[Federal Register Volume 73, Number 62 (Monday, March 31, 2008)]
[Notices]
[Pages 16924-16944]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-6600]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


Airworthiness Criteria: Airship Design Criteria for Zeppelin 
Luftschifftechnik GmbH Model LZ N07 Airship

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of issuance of final design criteria.

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SUMMARY: This document announces the issuance of final design criteria 
for the Zeppelin Luftschifftechnik GmbH model LZ N07 airship. The 
German aviation airworthiness authority, the Luftfahrt-Bundesamt (LBA), 
forwarded an application for type validation of the Zeppelin 
Luftschifftechnik GmbH Company KG (ZLT) model LZ N07 airship on October 
1, 2001. The airship will meet the provisions of the Federal Aviation 
Administration (FAA) normal category for airships operations and will 
be certificated for day and night visual flight rules (VFR); 
additionally, an operator of this airship may petition for exemption to 
operate the airship in other desired operations.

EFFECTIVE DATE: March 21, 2008.

FOR FURTHER INFORMATION CONTACT: Federal Aviation Administration, 
Attention: Mr. Karl Schletzbaum, Project Support Office, ACE-112, 901 
Locust, Kansas City, Missouri 64106; telephone: 816-329-4146; e-mail: 
[email protected]; facsimile (816) 329-4090.

SUPPLEMENTARY INFORMATION: 

Background

    Under the provisions of the Bilateral Aviation Safety Agreement 
(BASA) between the United States and Germany, the German aviation 
airworthiness authority, the Luftfahrt-Bundesamt (LBA), forwarded an 
application for type validation of the Zeppelin Luftschifftechnik GmbH 
Company KG (ZLT) model LZ N07 airship on October 1, 2001. The LZ N07 
has a rigid structure, 290,330 cubic foot displacement and has 
accommodations for twelve passengers and two crewmembers. The airship 
will meet the provisions of the FAA normal category for airships; 
additionally, an operator of this airship may petition for exemption to 
operate the airship in other desired operations. The airship will be 
certificated for day and night visual flight rules (VFR).

Discussion of Comments

    On April 10, 2007, the Federal Aviation Administration issued a 
notice of availability of proposed airworthiness design criteria for 
the ZLT model LZ N07 airship. The criteria was the certification basis 
accepted for the U.S. validated of the airship according to 14 CFR part 
21, Sec.  21.17(b). This criteria consisted of the German national 
standard Luftt[uuml]chtigkeitsforderungen f[uuml]r Luftschiffe der 
Kategorien Normal und Zubringer (LFLS) [Airworthiness Requirements: 
Normal and Commuter Category Airships] and equivalent requirements 
identified by the national aviation authority of Germany, the LBA.
    The notice was published for public comment on May 3, 2007 (72 FR 
24656). The comment period closed on June 4, 2007.
    A commenter from the airship design industry requested that we 
extend the comment period for the proposed design criteria. We agreed 
and issued the reopening of the comment period on July 7 and published 
a notice on July 16, 2007 (72FR 38858).
    Three commenters provided their comments on the notice. While the 
notice was not a notice of a regulatory change or requirement, the FAA 
is responding to the comments.
    Two commenters came from firms that proposed to operate airships. 
These comments were supportive of the standard and the process.
    The third commenter came from an airship manufacturer, which 
provided extensive comments as discussed below in the sections of the 
LFLS.

General Comment

    In its decision to accept the German LFLS certification 
requirements, the FAA has stated, ``the LFLS requirements are at least 
equivalent to and, in many cases, more conservative than the 
requirements for the normal category contained in the ADC.'' The LFLS 
requirements are for an airship designed to meet a ``commuter'' 
category for carrying passengers, hence a higher level of safety is 
appropriate. [Note: ADC means Airship Design Criteria.]
    By this statement, it is implied that the ZLT airship will meet a 
higher standard of certification, where in fact, the airship does not 
currently meet several critical safety requirements in both the LFLS 
and FAA-P-8110-2 Design Criteria. It has, therefore, been designed and 
accepted to a lesser standard.
    More importantly, several of the claims by ZLT to demonstrate an 
equivalent level of safety are not supported by reasonable argument but 
are really requests for exemption. They are also at odds with FAA 
determinations in previous U.S. airship certification programs in 
critical areas affecting safety of flight and in FAA efforts for 
standardization.
    In reviewing the ZLT exemptions, it also became apparent that the 
Zeppelin airship design is a significant departure from a conventional 
non rigid design. The industry and the FAA understand that the 
designation of conventional non rigid design implies a certain level of 
capability, especially in emergency conditions, and, therefore a 
certain level of operating environment has been granted. If the 
applicant continues to seek exemptions or if these exemptions are 
granted, it is more appropriate to call this airship a hybrid and, 
thus, issue special operating limitations, which limit the regime it 
can fly in.
    Generally, it is not understood why such latitude is being 
contemplated. In previous U.S. airship certification programs, the FAA 
has rigidly applied, and the airship industry has rigidly complied with 
certain fundamental airship certification requirements with no 
exemptions being granted. The ZLT airship certification program in 
Germany does not appear to have met some of these basic requirements. 
In addition, the FAA would appear to be

[[Page 16925]]

accepting the airship on the basis of the LFLS certification program 
without close scrutiny of the merits of the ZLT arguments for an 
equivalent level of safety.
    By accepting the ZLT claims, a precedent would be set. To compound 
the matter, the claims for a dispensation against the requirements are 
numerous in these critical safety areas, thereby having a cumulative 
affect and potentially compromising safety.
    FAA Response: The FAA reviewed the LFLS and the differences from 
this standard as applied by the LBA. We then, compared them to the 
currently accepted airship design criteria, the FAA-P-8110-2 Airship 
Design Criteria. The LFLS, with the additional or equivalent 
requirements applied by the LBA to the Zeppelin N07-100 (now referred 
to as the certification basis), was determined to provide the level of 
safety specified in 14 CFR part 21, Sec.  21.17(b).
    The certification basis criteria, as summarized in the notice, is 
accepted by the FAA as providing an equivalent level of safety, as 
specified by the 14 CFR part 21, Sec.  21.17(b), and is the accepted 
airworthiness criteria for the ZLT LZ N07-100 as defined in that part. 
In accepting this certification basis, the FAA considered the entire 
proposed certification basis, and does not consider equivalent levels 
of safety (for specific regulations), special conditions, or exemptions 
in this process, as the need to issue such regulatory processes are not 
required when accepting an airworthiness criteria in total for a 
special class aircraft. In this case, a criterion that had not been 
previously accepted, along with equivalencies granted by the local 
authority, was accepted as the airworthiness criteria and is the 
certification basis for this special class aircraft.
    The ZLT N07-100 airship is a rigid type airship that is capable of 
operations that have been previously type certificated by the FAA; the 
rigid structure is the only design feature that has not previously been 
type certificated. The FAA considers the noticed criteria suitable for 
the ZLT LZ N07 airship and does not consider it a hybrid type.

Technical Comments

    The commenter continued with specific technical comments on the 
notice criteria:
    These fundamental certification requirements where ABC [American 
Blimp Corporation] considers that ZLT are claiming an unreasonable 
equivalent level of safety are identified as follows:
    1. LFLS Section 881(a) and ADC paragraph 3.4--Proof of Structure
    2. LFLS Section 76 and ADC paragraph 2.11 Engine Failure and 
Ballast Requirements
    3. LFLS Section 893(b) and ADC paragraph 4.49 Ballast Requirements 
during Normal Flight.
    4. LFLS Section 143(b) and ADC paragraph 2.14(b)--No Engines--Safe 
Descent
    5. LFLS Section 673(d) and ADC paragraph 4.14(d)--No Mech Linkage--
Dual Redundancy.
    6. LFLS Section 881 (f) and ADC paragraph 4.43 (f)(g) Emergency 
Deflation
    7. LFLS Section 883(e) and ADC paragraph 4.44(e)--Air to helium 
Provision
    8. LFLS Section 2498(b) and ADC paragraph 6.25 Position Lighting
    (1) Comment:
    With respect to item 1 above, the commenter stated:

LFLS Section 881(a) and ADC paragraph 3.4--Proof of Structure

    The LFLS section 881(a) Envelope design requirement states that 
``The envelope must be designed to be pressurized and maintain 
sufficient super pressure (amount of envelope pressure in excess of 
ambient pressure) to remain in tension while supporting the limit 
design loads for all flight conditions and ground conditions''. ZLT 
claims that they should be exempt from this requirement because the 
structural integrity of the LZ N07 airship is not dependent on the 
envelope tension but on the structural integrity of the rigid 
structure. The structure must, therefore, be subject to a full 
structural load analysis and full-scale structural tests to ensure it 
meets the requirement. We are assuming that the FAA will verify that 
full-scale structural tests were carried out. (The ADC paragraph 3.4 
Proof of Structure requirement is very specific in this regard and 
states, ``Compliance with the strength and deformation requirements 
must be shown for each critical load condition. Structural analysis may 
be used only if the structure conforms to those for which experience 
has shown this method to be reliable.'')

FAA Response

    Under the Bilateral Aviation Safety Agreement (BASA) between the 
FAA and the LBA, the FAA can accept the provisions of the proposed 
certification basis and the method of compliance accepted by the LBA. 
In this case, the alternate requirements imposed by the LBA for LFLS 
section 881(a) are considered acceptable; the method of compliance was 
also accepted. The corresponding LFLS section to ADC section 3.4 is 
LFLS section 307. Compliance for these sections was accepted as applied 
by the LBA. A review of the LFLS requirements shows that structural 
testing is required for certain parts of the structure.
    (2) Comment:
    With respect to items 2 and 3 above, the commenter stated:

LFLS Section 76 and ADC Paragraph 2.11--Engine Failure and Ballast 
Requirements and LFLS 893(b) and ADC Paragraph 4.49--Ballast 
Requirements During Normal Flight

    The ADC paragraph 2.11 states ``The airship must be capable of 
rapidly restoring itself to a state of equilibrium following failure of 
one or more engines during any flight condition. Only designated 
ballast may be used.'' The FAA states ``ZLT met this requirement with 
an equivalent level of safety'' by demonstrating that a zero vertical 
speed condition can be established for any flight condition, by using 
the thrust vectoring capability of the remaining engines. Being able to 
only do this on one engine not on more engines is not equivalent. This 
equivalent level of safety claim ignores the essential airship 
capability to conduct a free balloon safe landing as required by LFLS 
893(b) and ADC paragraph 4.49.
    This requirement is applied to not only single engine failure but 
also the all-engine failure condition. The FAA in all previous Airship 
Certification programs in the U.S. has rigidly applied the requirement 
primarily because it is based on the airship's inability to glide to a 
safe landing or conduct an autorotation as in a helicopter.
    FAA Response:
    LFLS section 76 is slightly different than the ADC, in that the 
LFLS allows for the failure ``of any engine'' and the ADC specifies the 
failure of ``one or more engines.'' As the goal of the requirement is 
interpreted to be attaining a zero descent rate, the use of vectored 
thrust, as accepted by the LBA, was also accepted by the FAA as an 
acceptable approach.
    The provisions of LFLS section 893 apply if a ballast system is 
installed. The LZ N07-100 airship has a water ballast system, but it is 
not approved for in-flight use. For this reason, this section was not 
applied to the LZ N07-100 by the LBA. The FAA has accepted this 
position.
    (3) Comment:
    With respect to item 4, the commenter stated:

[[Page 16926]]

LFLS Section 143(b)--Safe Descent

    Section 143(b) and ADC paragraph 4.49 state that ``It must be shown 
that without engine power, a safe descent and landing under the 
conditions of section 561 can be made'' In the ZLT narrative, it is 
stated ``With the airship heavy there is no means to modulate the 
descent * * *.'' This (flying heavy) is a choice made by the applicant 
to make the airship more economically viable.
    The equivalent level of safety argument that ``A qualitative safety 
analysis will be performed to show that the simultaneous occurrence of 
a loss of all engines (combined with worst case weight conditions) is 
extremely improbable'' is inaccurate. It is not unrealistic to expect a 
total engine failure at maximum heaviness, as could be the case with 
fuel contamination. Indeed, total engine failure was experienced in an 
airship in the U.S. leading to a free balloon landing. This accident 
occurred one hour into the cross-country flight with the airship in a 
heavy static weight condition.
    Once again, the provisions of this and the previous LFLS section 76 
and ADC paragraph 2.11 are a basic airship design requirement and based 
on the airships inability to glide or conduct an autorotation. It is 
required to also protect people and property on the ground and not just 
the occupants of the airship. If the applicant continues to choose to 
seek an exemption to the safety requirements of a blimp it is more 
appropriate to call this airship a hybrid and thus issue special 
operating limitations, which limit the regime it can fly in to 
unpopulated areas or at higher altitudes over populated areas.
    FAA Response:
    LFLS section 143 is the applicable requirement which was again 
subject to an equivalent level of safety issued by the LBA, which 
allowed an analysis to show that an all engine failure in conjunction 
with the maximum heaviness was extremely improbable. This approach was 
also accepted by the FAA. It should be noted that even with all engines 
inoperative, the airship is still in compliance with LFLS section 561, 
Emergency Landing Conditions, General. As previously stated, the FAA 
does not consider this airship a hybrid type.
    (4) Comment:
    With respect to item 5 above, the commenter stated:

LFLS Section 673(d) and ADC Para 4.14(d)--No Mechanical Linkage--Dual 
Redundancy

    The LFLS section 673(d) requires that airship without a direct 
mechanical linkage between the cockpit and primary surfaces, be 
designed with a dual redundant control system. ABC does not understand 
why the following statement is made ``dual redundant is considered 
ambiguous in that it does not clearly define the degree of redundancy 
required.'' A dual redundant flight control system is a relatively 
straightforward concept that has been incorporated in many aircraft and 
the requirement seems quite unambiguous.
    It is also stated that compliance will be shown as ``continued safe 
flight and landing is assured after complete failure of any one of the 
primary flight control system lanes.'' This ignores the requirements of 
LFLS section 683(c) for the ``hard over'' condition. Any demonstration 
must include one of the control fins in a hard-over condition and not 
just one failed lane. The argument that vectored thrust is part of the 
primary flight control system then means that it too must comply with 
Dual Redundancy. Any use of vectorable engines is going to compromise 
the ability to maintain forward speed and limit this recovery 
capability.
    FAA Response:
    LFLS section 673(d) is the applicable requirement, in this case the 
LBA referred to the requirements for analysis for the control systems 
as specified in LFLS 1309 as adequate substantiation to show that 
compliance with LFLS 673(d) had been met. The design of the fly-by-wire 
control system of the airship was found to be compliant with LFLS 
673(d) when considering that the control system was compliant with LFLS 
1309. The FAA concurred with the approach.
    (5) Comment:
    With respect to item 6 above, the commenter stated:

LFLS Section 881(f) and ADC paragraph 4.43(f)(g)--Emergency Deflation

    LFLS Section 881(f) requires that provisions be maintained to allow 
for rapid envelope deflation on the airship should it break loose from 
the mast. ZLT's airship does not meet this requirement. ZLT's claim 
that the masthead design is fail proof is irrelevant if the airship 
tears apart behind the nose section and departs the mooring mast. It is 
not understood why this important design feature is not incorporated 
for the other reason that it can be used to ensure the airship stays on 
the ground in any emergency egress of passengers. This again, is a 
basic design requirement that, coupled with concessions against other 
design issues, adds to an overall compromised design standard. There is 
no reason this cannot be incorporated.
    FAA Response:
    The ADC and LFLS sections fundamentally have the same requirement. 
As the LZ N07-100 is a rigid type, envelope deflation is not considered 
a possible option in meeting the safety requirement of these sections. 
The LBA accepted that an analysis showing the safe life design of the 
mooring mast and its systems would be adequate to meet this requirement 
on an equivalent basis. The FAA accepted this as equivalent, with the 
additional requirement that the applicant also provide additional 
ground procedures for handling the airship on the ground, transponder 
activation and notification procedures in the case the airship was lost 
from the mast.
    (6) Comment:
    With respect to item 7 above, the commenter stated:

LFLS Section 883(e) and ADC Para 4.44(e)--Air to Helium Provision

    LFLS section 883(e) and ADC paragraph 4.44(e) requires that 
provisions be maintained to blow air into the helium space in order to 
prevent wrinkling of the envelope. The other purpose is to prevent the 
ballonet from overfilling and possibly rupturing. The ZLT airship does 
not meet this requirement. In the case of the ZLT airship, one of the 
ballonets rupturing could bring about a large center of gravity shift. 
This again, is a basic and essential airship requirement that should 
have been met.
    FAA Response:
    Again, the ADC and LFLS sections fundamentally have the same 
requirement. As the LZ N07-100 is a rigid type, pressurization of the 
envelope to prevent envelope wrinkling is not applied, as the rigid 
structure eliminates the need for this requirement. With respect to 
ballonet rupturing and center of gravity issues, this issue is not 
identified as a compliance goal for this section.
    (7) Comment:
    With respect to item 8, the commenter stated:

LFLS Section 2498(b) and ADC Para 6.25--Position Lighting

    LFLS Section 2498(b) and ADC paragraph 6.25 specify the position 
lighting requirements for airships. It is not understood why a 
dispensation should be given for something that can be easily fixed 
with properly TSO'd LED or similar lighting. ABC had to go through a 
stringent certification of the lighting on the one model. This was 
revisited in a new model and the FAA

[[Page 16927]]

asked ABC to modify our position lighting by providing two sets of bow 
lights in slightly different positions to further ensure adequate 
brilliance in all sectors. It is not understood why any latitude is 
being given to this basic legal requirement affecting safe navigation 
of aircraft.
    FAA Response:
    The FAA notes that there is no LFLS section 2498(b) and that the 
comparable LFLS section to ADC section 6.25 is LFLS section 1385. The 
only section where an equivalent level of safety to the LFLS lighting 
requirements was granted by the LBA is LFLS section 1387(b). The LBA 
granted this equivalency based on what was considered compensating 
features of the lighting system installed on the LZ N07-100, and the 
FAA agreed.

Conclusion

    After review of the provided comments, the FAA sees no need to 
modify the proposed airworthiness criteria. Accordingly, the 
airworthiness criteria, as issued on April 10, 2007, is adopted as the 
certification basis for the ZLT LZ N07-100 airship under the provisions 
of 14 CFR part 21, Sec.  21.17(b).
    The design criterion is shown below:

Design Criteria

Applicable Airworthiness Criteria Under 14 CFR part 21

    The only applicable requirement for airship certification in the 
United States is FAA document FAA-P-8110-2, Airship Design Criteria 
(ADC). This document has been the basis of bilateral validation of 
airships between Germany and the United States for many years. However, 
in 1995, the LBA issued the initial version of the 
Luftt[uuml]chtigkeitsforderungen f[uuml]r Luftschiffe der Kategorien 
Normal und Zubringer, (hereafter referred to as the LFLS), which added 
a commuter category to German airship categories and also added 
additional requirements for normal category airships. Due to this, 
where the previously mutually accepted ADC can be considered to be 
harmonized in practice, the issuance of the LFLS created regulatory 
differences for normal category airships between the United States and 
Germany.
    In keeping with its bilateral obligations, the FAA has, with 
assistance from the LBA, determined that regulatory differences exist 
between the two requirements (ADC versus LFLS). This determination is 
the Significant Regulatory Differences analysis. In the case of the LZ 
N07 airship, the German certification was accomplished to the higher 
standard of the commuter category of the LFLS, with various LBA 
modifications and additions. The FAA desires to accept the Zeppelin 
airship model LZ N07 at the same airworthiness standard as it was 
certificated to in Germany, so we have decided to accept the 
requirements of the LFLS and the supplemental requirements issued by 
the LBA as the U.S. certification basis. With this decision, the bulk 
of the regulatory differences are not relevant, as the FAA is accepting 
the provisions of the German LFLS certification in the commuter 
category in its entirety. The FAA has, after comparing the normal 
category ADC to the commuter category LFLS requirements, determined 
that all of the LFLS requirements are at least equivalent to and, in 
many cases, more conservative than the requirements for normal category 
contained in the ADC.

Regulatory Differences

    The LFLS was developed considering the ADC at Change 1, but Change 
2 provisions were not considered. There will be one regulatory 
difference due to this; ZLT will show compliance to ADC Sec.  4.14 at 
Change 2.

Additional and Alternative Requirements

    The German aviation authority, the Luftfaht-Bundesamt (LBA) issued 
additional requirements, special conditions, and equivalent levels of 
safety to deal with certain design provisions and airworthiness 
concerns specific to the design of the LZ N07 that were not anticipated 
by the LFLS. These requirements will also become part of the U.S. 
certification basis for this airship.
    The U.S. certification basis for the LZ N07 was proposed as an 
entire certification basis, including those changes required by the FAA 
and the LBA. Based on the provisions of 14 Code of Federal Regulations 
(CFR) part 21, Sec. Sec.  21.17(b), 21.17(c) and 21.29, the following 
airworthiness requirements were evaluated and found applicable, 
suitable, and appropriate for this design, and they remained active 
until August 31, 2007, the FAA has now extended the project termination 
date to May 31, 2008 and the requirements will stay active until that 
date.
    The German regulation Luftt[uuml]chtigkeitsforderungen f[uuml]r 
Luftschiffe der Kategorien Normal und Zubringer, (referred to as the 
LFLS), effective April 13, 2001; except:
    (1) In lieu of compliance to LFLS Sec.  673 the LZ N07 will comply 
with ADC Sec.  4.14.
    (2) B-1 LBA, Equivalent Safety Finding for Sec.  76 LFLS, Engine 
Failure.

Discussion

    The LFLS requires that the airship restore itself to a state of 
equilibrium after the failure of any one engine during any flight 
condition. In the case of the LZ N07, a state of equilibrium using 
designated ballast cannot be achieved as required by the LFLS. ZLT met 
this requirement with an equivalent level of safety.
    In lieu of the provisions of LFLS Sec.  76 the following is 
required:
    In the case of failure of any one engine (of three) it must be 
shown that a zero vertical speed condition can be established for any 
flight condition by using the thrust vectoring capability of the 
remaining two engines and aerodynamic lift.
    The time to achieve this zero vertical speed will be demonstrated 
to be not more than when using a designated ballast system with a 
minimum discharge rate established in LFLS Sec.  893(d).
    (3) B-2 LBA, Equivalent Safety Finding for LFLS Sec.  143(b), 
Controllability and Maneuverability, General [all engines out].

Discussion

    LFLS Sec.  143(b) requires that the airship be capable of a safe 
descent and landing after failure of all engines under the conditions 
of LFLS Sec.  561. ZLT met this requirement with an equivalent level of 
safety.
    Even in the event of all engines failing, a limited means to 
control the descent of the airship is available, but only with the 
airship in equilibrium. With the airship heavy, there is no means to 
modulate the descent once speed has dissipated, since the descent rate 
is determined by heaviness only. However, descent will be stable and no 
unsafe attitude will result and the worst-case descent rate is still in 
compliance with the emergency landing conditions of LFLS Sec.  561. 
This fulfills the safety objective of LFLS Sec.  143(b).
    To satisfy the provisions of LFLS Sec.  143(b), the following is 
required:
    A qualitative safety analysis will be performed to show that the 
simultaneous occurrence of a loss of all engines (combined with worst 
case weight conditions) is extremely improbable.
    (4) B-3 LBA, Equivalent Safety Finding for LFLS Sec.  33(d)(2), 
Propeller Speed and Pitch Limits.

Discussion

    LFLS Sec.  33(d)(2) requires a demonstration with the propeller 
speed control inoperative that there is a means to limit the maximum 
engine speed to

[[Page 16928]]

103 percent of the maximum allowable takeoff rotations per minute 
(rpm). The LZ N07 is designed so that in case of a zero thrust 
condition in flight, the affected engine is shut off. The shutoff rpm 
is above 103 percent of the maximum allowable takeoff rpm.
    The LZ N07 airship is not equipped with a traditional propeller 
governor system. The propeller speed control function is provided by 
the AIU (engine control board). If the AIU fails, a means to shut down 
the engine is provided: called the Limiting System (Lasar). The 
limiting system provides two functional stages; the first stage limits 
rpm between 2725 and 2750, in case the AIU engine control board is 
unable to limit engine speed with the propeller in zero thrust pitch 
condition. The second stage shuts down the engine at 2900 rpm in case 
of limiting system first stage failure in order to avoid engine and 
propeller disintegration hazard to the airship. The shutdown of one 
engine is considered a major hazard. (Note: maximum rpm = 2700, 103 
percent maximum rpm = 2781.)
    In traditional governor systems during in-flight operation with 
zero thrust pitch selected, overspeed protection is not assured in case 
of a governor failure. The LZ N07 design is considered to provide 
equivalent or improved safety compared to previously certified 
(traditional) governor systems.
    To satisfy the provisions of LFLS Sec.  33(d)(2), the following is 
required:
    The proper function of the systems will be demonstrated by 
performing a system ground test simulation.
    The propeller overspeed capability of 126 percent of the maximum 
rpm will comply with the provisions of JAR P certification, (JAR P 
Sec.  170(a)(2)).
    (5) B-4 LBA, Equivalent Safety Finding for LFLS Sec.  145, 
Longitudinal Control.

Discussion

    LFLS Sec.  145 requires a demonstration of nose-down pitch change 
out of a stabilized and trimmed climb and 30 degree pitch angle at 
maximum continuous power and a nose-up pitch change out of a stabilized 
and trimmed descent and -30 degree pitch angle at maximum continuous 
power on all engines. ZLT met this requirement with an equivalent level 
of safety. The LZ N07 ballonet system limitations prevent stabilized 
climbs or descents above certain vertical speeds. The procedure 
required in LFLS Sec.  145 cannot be demonstrated by flight test 
without modification.
    ZLT demonstrated through flight test that sufficient control 
authority was available to recover from a steep climb or descent when 
the airship is trimmed for the appropriate climb or descent and is 
operated under maximum continuous power.
    Additionally, it was also shown that it is possible to produce a 
nose-down pitch change out of a stabilized and trimmed climbing flight 
and a nose-up pitch change out of a similar descent. The LZ N07 
ballonet systems limitations prevent this from being demonstrated at 
maximum continuous power and 30-degree pitch angle because the climb or 
descent rates are too high at the resulting airspeed.
    To satisfy the provisions of LFLS Sec.  145 the following is 
required:
    A flight test procedure will demonstrate that it is possible to 
produce:
    (1) A nose-down pitch change out of a stabilized climb with a nose-
up flight path angle as limited by the ballonet system for the relevant 
true airspeed or 30 degrees, whichever leads to a lower absolute value.
    (2) A nose-up pitch change out of a stabilized descent with a nose-
down flight path angle as limited by the ballonet system for the 
relevant true airspeed or -30 degrees, whichever leads to a lower 
absolute value.
    (6) C-1 LBA, Additional Requirement for a Reliable Load Validation; 
14 CFR part 25, Sec.  25.301(b).

Discussion

    The present LFLS does not include the requirement for the 
manufacturer to validate the load assumptions used for stress analyses. 
14 CFR part Sec.  25.301(b) requires that methods used to determine 
load intensities and distribution must be validated by flight load 
measurement unless the methods used for determining those loading 
conditions are shown to be reliable.
    The following is added as an additional requirement:
    The provisions of 14 CFR part 25, Sec.  25.301(b) will be complied 
with.
    (7) D-1 LBA, Additional Requirements for LFLS Sec.  853(a), 
Compartment Interiors [Flammability of Seat Cushions].

Discussion

    LFLS Sec.  853 does not provide requirements for flammability 
standards for seat cushions as introduced by Amendment 59 of 14 CFR 
part 25. The LBA requested a proof test for seat cushions with the oil 
burner as specified in 14 CFR part 25, Appendix F, part II or 
equivalent for passenger seats, except for crew seats.
    To satisfy the provisions of LFLS Sec.  853(a), the following is 
required:
    A proof test for seat cushions with the oil burner as specified in 
14 CFR part 25, Appendix F, part II or equivalent for passenger seats 
will be performed successfully.
    (8) D-5 LBA, Additional Requirements for LFLS Sec.  673(d), Primary 
Flight Controls.

Discussion

    LFLS Sec.  673(d) requires that airships without a direct 
mechanical linkage between the cockpit and primary flight control 
surfaces be designed with a dual redundant control system. The 
terminology ``dual redundant'' is considered ambiguous in that it does 
not clearly define the degree of redundancy required.
    To satisfy the provisions of LFLS Sec.  853(a), the following is 
required:
    Compliance with LFLS Sec.  1309 will show that continued safe 
flight and landing is assured after complete failure of any one of the 
primary flight control system lanes.
    (9) D-6 LBA, Equivalent Safety Finding for LFLS Sec.  771(c), Pilot 
Compartment [Controls Location with Respect to Propeller Hub].

Discussion

    LFLS Sec.  771(c) requires that aerodynamic controls and pilots may 
not be situated within the trajectories of the designated propeller 
burst area. Since a thrust vectoring (including a non-swiveling lateral 
propeller) system has been incorporated into the airship, with two 
engines forward and one aft engine, formal non-compliance in some cases 
cannot be avoided.
    To satisfy the provisions of LFLS Sec.  771(c), the following is 
required:
    A qualitative safety analysis will be accomplished that considers 
the mitigating effects of:
    (1) The relationship of overall swivel angle of propeller 
rotational plane versus crucial swivel angle of propeller rotational 
plane,
    (2) The distance between aft propeller and aerodynamic controls, 
and
    (3) The potential energy absorbing and deflecting structure between 
aft propulsion unit and controls and pilot.
    The analysis will consider the following:
    The lateral propeller is continuously operating in idle with the 
exception of ground maneuvering and approach phases.
    The rear propeller transitions through its crucial angle only, 
while swiveling from the horizontal to the vertical position from a 
takeoff/approach/landing/hover to a level flight configuration.
    Aircraft Flight Manual (AFM) procedures, cockpit placarding, and 
swivel lever markings shall be

[[Page 16929]]

established to restrict normal operation in the crucial swivel range.
    (10) D-7 LBA, Equivalent Safety Findings for LFLS Sec.  777(c), 
Cockpit Controls; 1141(a), Powerplant Controls: General; 1143(c), 
Engine Controls; 1149(a)(2), Propeller Speed and Pitch Controls; 
1167(c)(1), Vectored Thrust Controls.

Discussion

    LFLS Sec.  777(c), 1141(a), 1143(c), 1149(a)(2), and 1167(c)(1) all 
involve requirements governing the configuration and characteristics of 
throttle, propeller pitch, mixture, and thrust vectoring controls. Due 
to the constant speed throttle control concept allowing infinitely 
variable thrust vector control between maximum reverse and maximum 
forward thrust, a non-conventional control system was developed that is 
partially non-compliant with the requirements. The requirements and the 
configuration of the LZ N07 are summarized in Table 1 below.
    To satisfy the provisions of LFLS Sec.  777(c), 1141(a), 1143(c), 
1149(a)(2) and 1167(c)(1) the following is required:
    In the case of an identified non-compliance to the LFLS, as shown 
in Table 1, compliance will be by an evaluation of the airship and a 
finding that there are safe handling characteristics using the type 
design engine thrust control/thrust vectoring controls as described in 
Table 1.

                                                     Table 1
----------------------------------------------------------------------------------------------------------------
                                                      Compliant/non-         Description of equivalent level of
    LFLS paragraph            Requirement               compliant                     safety finding
----------------------------------------------------------------------------------------------------------------
 777(c)..............   throttle, propeller       1. non-compliant......   Propeller speed, thrust, and mixture
                        pitch, mixture            2. compliant..........   controls are arranged in this order
                        controls:.                                         from left to right. Propeller speed
                        1. order left to right.                            and mixture are grouped together
                        2. arrange to prevent                              forward of the THRUST levers because
                        confusion.                                         they are preset for individual
                                                                           operating conditions. The THRUST
                                                                           levers are located separately with
                                                                           the L/H and R/H THRUST levers and
                                                                           swivel controls grouped together in
                                                                           order to achieve convenient vector
                                                                           operation.
                                                                           Rear engine thrust control set is
                                                                           offset to the rear of the center
                                                                           pedestal, which makes its allocation
                                                                           to the rear engine obvious.
 1141(a).............   1. arrangement like 777   1. compliant as          See 777(c) above; compliant.
                        2. markings like          described above.
                        1555(a).                  2. compliant..........
 1143(c).............   1. separate control of    1. compliant..........   1. compliant
                        engines.                  2. simultaneous          2. simultaneous control of forward
                        2. simultaneous control   control virtually        engines allows for symmetric thrust
                        of engines.               compliant.               applications, which are essential for
                                                                           effective handling of the airship.
                                                                           The aft engine THRUST lever is not
                                                                           located between the forward THRUST
                                                                           levers because it requires individual
                                                                           control especially during take-off,
                                                                           hover, landing and ground
                                                                           maneuvering. Unintentional operation
                                                                           of the aft engine is prevented by
                                                                           this arrangement.
 1149(a).............   simultaneous speed and    Non-compliant for take-  In contrast to conventional propeller
                        pitch control of          off, hover, landing,     controls, a constant propeller pitch
                        propellers.               and ground maneuvering.  is commanded directly by the THRUST
                                                                           lever and propeller speed is
                                                                           preselected by the RPM lever and is
                                                                           automatically governed by means of
                                                                           throttle variation.
                                                                           In this operating mode, full RPM is
                                                                           selected and pitch control is
                                                                           commanded directly from the THRUST
                                                                           levers, which are not grouped
                                                                           together, thus not allowing
                                                                           simultaneous pitch control. The
                                                                           reason for this arrangement is
                                                                           explained in issue 1143(c) above, In
                                                                           FLIGHT configuration maximum pitch is
                                                                           preselected by the THRUST levers,
                                                                           speed control is now accomplished by
                                                                           movement of the RPM levers, which are
                                                                           grouped together allowing
                                                                           simultaneous speed control.
 1167(c)(1)..........   Thrust vectoring:......   1. compliant..........   1. compliant.
                        1.--independent of        2. non compliant......   2. simultaneous vectoring control of
                        other controls.                                    forward engines allows for symmetric
                        2.--separate and                                   vectoring. Asymmetric control of
                        simultaneous control of                            forward swivel angle is made
                        all propulsion units.                              impossible in order to prevent pilot
                                                                           confusion during vector control.
                                                                           Aft swivel adjustment is limited to 0
                                                                           for cruise and -90 for T/L. The aft
                                                                           swivel is separated due to the
                                                                           individual control requirement.
----------------------------------------------------------------------------------------------------------------

    (11) D-8 LBA, Equivalent Safety Findings for LFLS Sec.  807(d) and 
Sec.  807(d)(1)(i), Emergency Exits.

Discussion

    LFLS Sec.  807(d) and (d)(1)(i) for commuter category airships 
carrying less than 15 passengers requires at least three emergency 
exits. Refer to Table 2.

                                                     Table 2
----------------------------------------------------------------------------------------------------------------
      Category versus exits                First exit                Second exit               Third exit
----------------------------------------------------------------------------------------------------------------
Normal Category (Less than 10      External door/Main door:   One exit 19 x 26 inches   No requirement.
 passengers.).                      Sec.   783(a) (19 x 26     opposite of main door:
                                    inches).                   Sec.   807(a)(1).

[[Page 16930]]

 
 Commuter Category (Less than 15   Main door must be floor    Same as above...........   In addition one exit 19
 passengers.).                      level: Sec.   807(d)(1).                             x 26 required.
 Commuter Category Zeppelin LZ     Floor level main door      Second floor level main   Not provided. Equivalent
 N07. Design comprising 12          much larger as 19 x 26     door much larger as 19    safety requested for
 passengers.                        inches provided.           x 26 inches provided.     greater than 9
                                                                                         passengers.
----------------------------------------------------------------------------------------------------------------

    The design of the LZ N07 fully complies with the requirement for 
the Normal Category; however, the third exit required for compliance in 
the Commuter Category is not provided. This results in a formal 
noncompliance.
    To satisfy the provisions of LFLS Sec.  807(d) and 807(d)(1)(i), 
the following is required:
    Compliance for LFLS Sec.  807(d) and 807(d)(1)(i) will be shown by:
    (1) The first and second exits provided are both floor level exits 
and oversized compared to 19 by 26 inches.
    (2) The evacuation demonstration required in Sec.  803(e) shall be 
accomplished within 60 seconds, (with one exit blocked) instead of 90 
seconds.
    (12) D-9 LBA, Equivalent Safety Finding for Sec.  881(a), Envelope 
Design [Envelope Tension].

Discussion

    LFLS Sec.  881(a) requires that the envelope maintain tension while 
supporting limit load conditions for all flight conditions. The rigid 
design of the LZ N07 allows for limited wrinkling of the envelope under 
limit load conditions with no effect on airship handling and 
performance.
    Due to the unique kind of rigid structural design, the structural 
integrity of the LZ N07 airship is not dependent on the tension of the 
envelope, as rigid structure replaces the load-carrying envelope. The 
alignment of structure, engines, empennage, cabin and other components 
affecting handling qualities, performance, and other factors is 
independent of any wrinkling condition of the envelope.
    To satisfy the provisions of LFLS Sec.  881(a), the following is 
required:
    Safe handling characteristics will be demonstrated by flight test, 
the limit load carrying capability by analysis.
    (13) D-10 LBA, Equivalent Safety Finding for LFLS Sec.  881(f), 
Envelope Design [Rapid Deflation Provisions].

Discussion

    LFLS Sec.  881(f) requires that provisions be maintained to allow 
for rapid envelope deflation of the airship should it break loose from 
the mast while moored. The present design does not include such a 
provision. For German certification, ZLT had to demonstrate an 
equivalent level of safety. As part of this, ZLT presented that, due to 
the unique kind of rigid structural design of the airship, any rapid 
deflation provision will not significantly reduce the effective cross 
section of the envelope; thus, the uncontrolled drift of the airship 
due to surface winds once free of its moorings could not be brought 
under control. ZLT presented that the overall level of safety is 
negatively affected by the potential unwanted operation of the required 
rapid deflation provision when unintentionally operated or operated due 
to individual failure conditions, and that this could lead to a 
potentially severe failure condition.
    ZLT was required by the LBA to provide an equivalent level of 
safety by means of a qualitative safety analysis and by showing that 
the reliability of the mast coupling system design is significantly 
improved over typical non-rigid airship systems. It also provided proof 
of safe life design for the structural parts and to prove the fail-safe 
design of the hydraulically powered locking mechanism. These systems 
are part of the ground based mooring vehicle.
    We understand that the rigid structure of the airship complicates 
or eliminates the deflation design feature expected of non-rigid types 
of airships, and we believe that this requirement cannot be met without 
an equivalent level of safety. The rapid deflation feature of a non-
rigid airship is provided to allow emergency egress without the ship 
lifting and to deflate the envelope in case an airship is blown off of 
the mast and is subsequently uncontrolled. These concerns still apply 
to a rigid airship.
    We accept the evacuation procedure, described in the section 
discussion LFLS Sec.  809(e), as an acceptable equivalent feature for 
the evacuation requirement.
    In the event that the airship is blown off of the mast, we believe 
that a rigid airship will present the same or enhanced hazard as the 
requirement for non-rigid type airships was developed to mitigate, that 
being of an unmanned and, or, uncontrolled airship in controlled 
airspace in the proximity of persons, property, or other aircraft.
    To satisfy the provisions of LFLS Sec.  881(f), the following is 
required:
    Safe life design for the structural parts and fail-safe design of 
the hydraulically powered locking mechanism of the mooring vehicle will 
be shown.
    The Airship Flight Manual will contain mast procedures for all 
approved mast mooring conditions. These procedures will also include a 
requirement to have transponder equipment active when the airship is 
moored on the mast, and define conditions when a pilot must be in the 
airship.
    (14) D-11 LBA, Equivalent Safety Finding for LFLS Sec.  883(e), 
Pressure System.

Discussion

    LFLS Sec.  883(e) requires that provisions be maintained to blow 
air into the helium space in order to prevent wrinkling of the 
envelope. The present design of the airship does not include this 
provision; therefore, ZLT had to demonstrate equivalent level of 
safety.
    Due to the unique kind of rigid structural design, the structural 
integrity of the airship is not dependent on the tension of the 
envelope. Rigid structure replaces the load-carrying envelope. The 
alignment of structure, engines, empennage, and cabin, etc., affecting 
handling qualities and airship controllability is independent of any 
wrinkling condition of the envelope.
    To satisfy the provisions of LFLS Sec.  883(e), the following is 
required:
    Safe operation at reduced helium pressures will be demonstrated.
    (15) D-12 LBA, Interpretation of LFLS Sec.  785(b), Seats, berths 
and safety belts [Approval of].

Discussion

    The LFLS requires approval for seats; the LBA required approval of 
passenger and crew seats according to TSO C39b. The ZLT uses seats that 
are TSO C39b approved by a seat vendor; if this is not done, the seats 
used will demonstrate compliance to TSO C39b.
    To satisfy the provisions of LFLS Sec.  758(b), the following is 
required:
    Seats will comply with the provisions of TSO C39b.

[[Page 16931]]

    (16) D-13 LBA, Additional Requirement; LFLS Sec.  1585(a)(10), 
Operating Procedures [Ditching, Emergency Evacuation].

Discussion

    The LFLS does not provide requirements for ditching exits; the LBA 
requested a floatation analysis to be done, to analyze the case of an 
unplanned ditching. Helium loss during the emergency evacuation 
procedure was not considered. It was determined by calculation that the 
passenger cabin provides enough buoyancy for safe egress with the 
requirement that one emergency exit shall be usable above the static 
waterline for at least 90 seconds for emergency evacuation.
    To satisfy the provisions of LFLS Sec.  758(b), the following is 
required:
    It shall be demonstrated by test or analysis that an emergency 
evacuation exit will remain above the waterline for at least 90 seconds 
after finally settling on the water. Relevant instructions will be 
included in the Airship Flight Manual.
    (17) D-14 LBA, Interpretative Material; LFLS Sec.  803(e), 
Emergency Evacuation Demonstration.

Discussion

    LFLS Sec.  803(e) requires an emergency evacuation demonstration. 
This evacuation must be completed within 90 seconds. Compliance with 
LFLS Sec.  881(g) must be considered in conjunction with Sec.  803(a) 
through (e).
    This requirement demonstrates the ability of the entire cabin to be 
evacuated within 90 seconds using the maximum number of occupants, with 
flight crew preparation for the emergency evacuation. Normal valving of 
helium to provide emergency deflation on the ground during the 
emergency evacuation, according to Sec.  881(g), is assumed.
    To satisfy the provisions of LFLS Sec.  803(e), the following is 
required:
    (1) It will be demonstrated that the cabin can be emergency 
egressed within 90 seconds.
    (2) In addition, the evacuation method established will include the 
preparation of the airship for the ground phase of the emergency 
evacuation on the ground. The applicant will demonstrate by analysis 
supported by tests that the preparation for cabin emergency evacuation 
could be conducted within 30 seconds (from time of landing until start 
of cabin emergency evacuation). This technique will be published in the 
AFM. Refer to Figure 1, ``ZLT Emergency Evacuation Technique.'' 
[GRAPHIC] [TIFF OMITTED] TN31MR08.000

    (3) The evacuation method established will include four steps:
    (a) After the occurrence of the emergency situation, the pilot has 
to prepare the airship for an emergency landing.
    (b) The pilot has to land the airship.
    (c) The pilot has to prepare the airship for the evacuation. This 
includes providing enough heaviness so that the airship cannot leave 
the ground during the passenger evacuation. Also, the pilot must keep 
the airship in a safe position before starting the evacuation. By 
controlling the deflation, the pilot must try to prevent trapping of 
the envelope over the occupants during the evacuation.
    (d) The actual evacuation will only begin when a safe position of 
the airship can be maintained and when enough heaviness is provided.
    These steps will be reflected in the AFM.
    (18) D-15 LBA, Additional Requirements; 14 CFR part 23, Sec. Sec.  
23.859 and 23.1181(d), [cabin heating; fuel burner].

Discussion

    ZLT wishes to install fuel burner heating equipment for a cabin 
heating and ventilation system in the lower shell of the passenger 
cabin. The LFLS does not provide adequate requirements for the 
installation of fuel burner equipment. The LBA required the application 
of 14 CFR part 23, Sec. Sec.  23.859 and 23.1181(d), revised as of 
January 1, 1998, in addition to other applicable requirements of the 
LFLS. The LBA interpretation of Sec.  23.859(a) is such that the entire 
heater compartment will be considered a fire region and has to be of 
fireproof construction. Part 23 Sec.  23.859, paragraphs (a)(1) to 
(a)(3), will be complied with also. Other applicable FAA regulations 
introduced by reference to Sec. Sec.  23.859 and 23.1181(d) by

[[Page 16932]]

the LBA will be complied with by compliance to applicable LFLS 
sections.
    The airship will comply with the provisions of 14 CFR part 23, 
Sec.  23.859, Combustion Heater Fire Protection, and Sec.  23.1181(d), 
Firewalls.
    (19) E-1 LBA, Additional Requirements Remote Propeller Drive 
System.

Discussion

    The LZ N07 propellers of both forward and aft propulsion systems 
are not conventionally installed directly on the engine crankshaft. A 
remote propeller drive system consisting of torque shafts, swivel 
gears, friction clutches and a belt drive unit (on the aft engine only) 
is installed between engine and propeller to provide thrust and vector 
capability for the propellers. The LFLS does not contain requirements 
for such power transmission designs.
    The LBA required compliance as described in LBA guidance paper I-
231-87, applicable to components installed between engines and 
propellers. I-231-87(01) requires compliance with JAR 22H or 14 CFR 
part 33; however, instead of JAR 22H or 14 CFR part 33 compliance, 
compliance with applicable sections of JAR P (Change 7) as listed in 
Table 3 will be required.

                               Table 3.--Applicable Sections of JAR P and I-231-87
----------------------------------------------------------------------------------------------------------------
                               Section                                                  Summary
----------------------------------------------------------------------------------------------------------------
I-231-87............................................................  Remote torque shafts/Fernwellen.
I-231-87(01)........................................................  Alle Bauteile zwischen Motor und Propeller
                                                                       FAR 33.
I-231-87(02)........................................................  Kr[auml]fte auf k[uuml]rzestem Weg in
                                                                       tragende Bauteile.
I-231-87(03)........................................................  Konstruktive Ma[beta]nahmen gegen
                                                                       ungleiche Dehnung.
I-231-87(04)........................................................  Bei Drehgelenken ungleichf[ouml]rm.
                                                                       Drehbewegung meiden.
I-231-87(05)........................................................  Abstand Struktur zu rotierenden Teilen
                                                                       >13mm.
I-231-87(06)........................................................  FVB: Erweichungstemperatur TGA nicht
                                                                       [uuml]berschreiten.
I-231-87(07)........................................................  Nicht feuersichere Wellen: Feuerschutz zum
                                                                       Motor.
I-231-87(08)........................................................  Keine Gef[auml]hrdung durch angetr. Rest
                                                                       gebroch. Welle.
I-231-87(09)........................................................  Unterkritischer Lauf/Kritische Drehzahl
                                                                       1,5*nmax.
I-231-87(10)........................................................  Schwingungsversuch mit Anla[beta]-
                                                                       Abstellvorg[auml]ngen.
JAR-P...............................................................  Propellers: Change 7, dated 22.10.87.
JAR-P01.............................................................  Section 1--Requirements.
JAR-P01 1A..........................................................  SUB-SECTION A--GENERAL
JAR-P030(a)(1)......................................................  Specification detailing airworthiness
                                                                       requirements.
JAR-P040(b).........................................................  Fabrication methods.
JAR-P040(b)(1)......................................................  Consistently sound structure and reliable.
JAR-P040(b)(2)......................................................  Approved process specifications, if close
                                                                       control required.
JAR-P040(c).........................................................  Castings.
JAR-P040(c)(1)......................................................  Casting technique, heat treatment, quality
                                                                       control.
JAR-P040(c)(2)......................................................  AA Approval for casting production
                                                                       required.
JAR-P040(e).........................................................  Welded structures and welded components.
JAR-P040(e)(1)......................................................  Welding technique, heat treatment, quality
                                                                       control.
JAR-P040(e)(3)......................................................  Drawings annotated and with working
                                                                       instructions.
JAR-P040(e)(4)......................................................  If required, radiographic inspection, may
                                                                       be in steps.
JAR-P070............................................................  Failure analysis.
JAR-P070(a).........................................................  Failure analysis/assessment of propeller
                                                                       and control systems.
JAR-P070(b)(2)......................................................  Significant overspeed or excessive drag.
JAR-P070(c).........................................................  Proof of probability of failure.
JAR-P070(e).........................................................  Acceptability of failure analysis, if more
                                                                       on 1 of:
JAR-P070(e)(1)......................................................  A safe life being determined.
JAR-P070(e)(2)......................................................  A high level of integrity, parts to be
                                                                       listed.
JAR-P070(e)(3)......................................................  Maintenance actions, serviceable items.
JAR-P080............................................................  Propeller pitch limits and settings.
JAR-P090............................................................  Propeller pitch indications.
JAR-P130............................................................  Identification.
JAR-P140............................................................  Conditions applicable to all tests.
JAR-P140(a).........................................................  Oils and lubricants.
JAR-P140(b).........................................................  Adjustments.
JAR-P140(b)(1)......................................................  Adjustments prior to test not be altered
                                                                       after verification.
JAR-P140(b)(2)......................................................  Adjustment and settings checked/
                                                                       unintentional variations recorded.
JAR-P140(b)(2)(i)...................................................  At each strip examination.
JAR-P140(b)(2)(ii)..................................................  When adjustments and settings are reset.
JAR-P140(b)(3)......................................................  Instructions for (b)(1) proposed for
                                                                       Manuals.
JAR-P140(c).........................................................  Repairs and replacements.
JAR-P140(d).........................................................  Observations.
JAR-P150............................................................  Conditions applicable to endurance tests
                                                                       only.
JAR-P150(a).........................................................  Propeller accessories to be used during
                                                                       tests.
JAR-P150(b).........................................................  Controls (ground and flight tests).
JAR-P150(b)(1)......................................................  Automatic controls provided in operation.
JAR-P150(b)(2)......................................................  Controls operated in accordance with
                                                                       instructions.
JAR-P150(b)(3)......................................................  Instructions provided in Manuals.
JAR-P150(c).........................................................  Stops (ground tests).
JAR-P160............................................................  General.
JAR-P160(b).........................................................  Pass without evidence of failure or
                                                                       malfunction.
JAR-P160(c).........................................................  Detailed inspection before and after tests
                                                                       complete.
JAR-P170(c).........................................................  Spinner, deicing equipment, etc., subject
                                                                       to same test.

[[Page 16933]]

 
JAR-P190(c).........................................................  Propellers fitted with spinner and fans.
JAR-P200............................................................  Rig tests of propeller equipment.
JAR-P200(a).........................................................  Tests for feathering, beta control, thrust
                                                                       reverse.
JAR-P200(b).........................................................  Test to represent the amount of 1000 hour
                                                                       cycles.
JAR-P200(c).........................................................  Evidence of similar tests may be
                                                                       acceptable.
JAR-P210............................................................  Endurance tests.
JAR-P210(b).........................................................  Variable pitch propellers.
JAR-P210(b)(1)......................................................  Variable pitch propellers tested to one of
                                                                       following:
JAR-P210(b)(1)(i)...................................................  A 110-hour test.
JAR-P210(b)(1)(i)(A)................................................  5 hours at takeoff power.
JAR-P210(b)(1)(i)(B)................................................  50 hours maximum continuous power.
JAR-P210(b)(1)(i)(C)................................................  50 hours consisting of ten 5-hour cycles.
JAR-P210(b)(2)......................................................  At conclusion of the endurance test total
                                                                       cycles.
JAR-P210(b)(2)(ii)..................................................  Governing propellers: 1500 cycles of
                                                                       control.
JAR-P210(b)(2)(iv)..................................................  Reversible-pitch propellers: 200 cycles +
                                                                       30 seconds.
JAR-P220............................................................  Functional tests not less 50 in flight.
JAR-P220(b).........................................................  Variable pitch (governing) propellers.
JAR-P220(b)(1)......................................................  Propeller governing system compatible w.
                                                                       engine.
JAR-P220(b)(2)......................................................  Stability of governing under various oil
                                                                       temperatures conditions.
JAR-P220(b)(3)......................................................  Response to rapid throttle movements,
                                                                       balked landing.
JAR-P220(b)(4)......................................................  Governing and feathering at all speeds up
                                                                       to VNE.
JAR-P220(b)(5)......................................................  Unfeathering, especially after cold soak.
JAR-P220(b)(6)......................................................  Beta control response and sensitivity.
JAR-P220(b)(7)......................................................  Correct operation of stops and warning
                                                                       lights.
JAR-P220(c).........................................................  Propeller design for operation in reverse
                                                                       pitch 50 landing.
----------------------------------------------------------------------------------------------------------------

    To satisfy the additional required provisions, the following is 
required:
    Compliance will be shown for the Remote Propeller Drive System to 
the requirements of LBA document I-237-87, dated September 1987, and 
the Joint Aviation Requirements (JARs) summarized in Table 3.

                                              Table 3.--(Repeated)
----------------------------------------------------------------------------------------------------------------
                               Section                                                  Summary
----------------------------------------------------------------------------------------------------------------
I-231-87............................................................  Remote torque shafts/Fernwellen.
I-231-87(01)........................................................  Alle Bauteile zwischen Motor und Propeller
                                                                       FAR 33.
I-231-87(02)........................................................  Kr[auml]fte auf k[uuml]rzestem Weg in
                                                                       tragende Bauteile.
I-231-87(03)........................................................  Konstruktive Mabnahmen gegen ungleiche
                                                                       Dehnung.
I-231-87(04)........................................................  Bei Drehgelenken ungleichfrm. Drehbewegung
                                                                       meiden.
I-231-87(05)........................................................  Abstand Struktur zu rotierenden Teilen
                                                                       >13mm.
I-231-87(06)........................................................  FVB: Erweichungstemperatur TGA nicht
                                                                       [uuml]berschreiten.
I-231-87(07)........................................................  Nicht feuersichere Wellen: Feuerschutz zum
                                                                       Motor.
I-231-87(08)........................................................  Keine Gef[auml]hrdung durch angetr. Rest
                                                                       gebroch. Welle.
I-231-87(09)........................................................  Unterkritischer Lauf/ Kritische Drehzahl
                                                                       1,5*nmax.
I-231-87(10)........................................................  Schwingungsversuch mit Anlab-
                                                                       Abstellvorg[auml]ngen.
JAR-P...............................................................  Propellers Change 7, dated 22.10.87.
JAR-P01.............................................................  Section 1--Requirements.
JAR-P01 1A..........................................................  SUB-SECTION A--GENERAL.
JAR-P030(a)(1)......................................................  Specification detailing airworthiness
                                                                       requirements.
JAR-P040(b).........................................................  Fabrication Methods.
JAR-P040(b)(1)......................................................  Consistently sound structure and reliable.
JAR-P040(b)(2)......................................................  Approved process specification, if close
                                                                       control required.
JAR-P040(c).........................................................  Castings.
JAR-P040(c)(1)......................................................  Casting technique, heat treatment, quality
                                                                       control.
JAR-P040(c)(2)......................................................  AA Approval for casting production
                                                                       required.
JAR-P040(e).........................................................  Welded Structures and Welded Components.
JAR-P040(e)(1)......................................................  Welding technique, heat treatment, quality
                                                                       control.
JAR-P040(e)(3)......................................................  Drawings annotated and with working
                                                                       instructions.
JAR-P040(e)(4)......................................................  If required, radiographic inspection, may
                                                                       be in steps.
JAR-P070............................................................  Failure Analysis.
JAR-P070(a).........................................................  Failure analysis/assessment propeller/
                                                                       control system.
JAR-P070(b)(2)......................................................  Significant overspeed or excessive drag.
JAR-P070(c).........................................................  Proof of probability of failure.
JAR-P070(e).........................................................  Acceptability of failure analysis, if more
                                                                       on 1 of:
JAR-P070(e)(1)......................................................  A safe life being determined.
JAR-P070(e)(2)......................................................  A high level of integrity, parts to be
                                                                       listed.
JAR-P070(e)(3)......................................................  Maintenance actions, serviceable items.
JAR-P080............................................................  Propeller Pitch Limits and Settings.
JAR-P090............................................................  Propeller Pitch Indications.
JAR-P130............................................................  Identification.

[[Page 16934]]

 
JAR-P140............................................................  Conditions Applicable to All Tests.
JAR-P140(a).........................................................  Oils and Lubricants.
JAR-P140(b).........................................................  Adjustments.
JAR-P140(b)(1)......................................................  Adjustment prior to test not be altered
                                                                       after verification.
JAR-P140(b)(2)......................................................  Adjustment and settings checked/
                                                                       unintentional variations recorded.
AR-P140(b)(2)(i)....................................................  At each strip examination.
JAR-P140(b)(2)(ii)..................................................  When adjustments and settings are reset.
JAR-P140(b)(3)......................................................  Instructions for (b)(1) proposed for
                                                                       Manuals.
JAR-P140(c).........................................................  Repairs and Replacements.
JAR-P140(d).........................................................  Observations.
JAR-P150............................................................  Conditions Applicable to Endurance Tests
                                                                       Only.
JAR-P150(a).........................................................  Propeller accessories to be used during
                                                                       tests.
JAR-P150(b).........................................................  Controls (Ground and Flight Tests).
JAR-P150(b)(1)......................................................  Automatic controls provided in operation.
JAR-P150(b)(2)......................................................  Controls operated in accordance with
                                                                       instructions.
JAR-P150(b)(3)......................................................  Instructions provided in Manuals.
JAR-P150(c).........................................................  Stops (Ground Tests).
JAR-P160............................................................  General.
JAR-P160(b).........................................................  Pass without evidence of failure or
                                                                       malfunction.
JAR-P160(c).........................................................  Detailed inspection before and after tests
                                                                       complete.
JAR-P170(c).........................................................  Spinner, deicing equipment, etc., subject
                                                                       to same test.
JAR-P190(c).........................................................  Propellers Fitted with Spinner and Fans.
JAR-P200............................................................  Rig Tests of Propeller Equipment.
JAR-P200(a).........................................................  Tests for feathering, Beta Control, thrust
                                                                       reverse.
JAR-P200(b).........................................................  Test to represent the amount of 1000 h
                                                                       cycles.
JAR-P200(c).........................................................  Evidence of similar tests may be
                                                                       acceptable.
JAR-P210............................................................  Endurance Tests.
JAR-P210(b).........................................................  Variable Pitch Propellers.
JAR-P210(b)(1)......................................................  Variable Pitch Propellers tested to one of
                                                                       following.
JAR-P210(b)(1)(i)...................................................  A 110-Hour Test.
JAR-P210(b)(1)(i)(A)................................................  5 hours at Takeoff Power.
JAR-P210(b)(1)(i)(B)................................................  50 hours Maximum Continuous Power.
JAR-P210(b)(1)(i)(C)................................................  50 hours consisting of ten 5-hour cycles.
JAR-P210(b)(2)......................................................  At conclusion of the Endurance Test total
                                                                       cycles.
JAR-P210(b)(2)(ii)..................................................  Governing Propellers: 1500 cycles of
                                                                       control.
JAR-P210(b)(2)(iv)..................................................  Reversible-pitch Propellers: 200 cycles +
                                                                       30 sec.
JAR-P220............................................................  Functional Tests not less 50 in flight.
JAR-P220(b).........................................................  Variable Pitch (Governing) Propellers.
JAR-P220(b)(1)......................................................  Propeller governing system compatible with
                                                                       engine.
JAR-P220(b)(2)......................................................  Stability of governing under various oil
                                                                       temperature conditions.
JAR-P220(b)(3)......................................................  Response to rapid throttle movements,
                                                                       balked landing.
JAR-P220(b)(4)......................................................  Governing and feathering at all speeds up
                                                                       to VNE.
JAR-P220(b)(5)......................................................  Unfeathering, especially after cold soak.
JAR-P220(b)(6)......................................................  Beta control response and sensitivity.
JAR-P220(b)(7)......................................................  Correct operation of stops and warning
                                                                       lights.
JAR-P220(c).........................................................  Propeller Design for Operation in Reverse
                                                                       Pitch 50 landing.
----------------------------------------------------------------------------------------------------------------

LBA DOCUMENT I-237-87

Preliminary Guideline for Compliance of Transmission-Shafts in 
Powerplant Installations of Airplanes (Part 23) and Powered 
Sailplanes (JAR 22)

LBA-Document: I231-87
Issue: 30. September 1987
Change record: translated into English, May 2002

Translation has been done by best knowledge and judgment. In any 
case, the officially published text in German language is 
authoritative.

    At the present time the Airworthiness Requirements for motorized 
aircraft assume only propeller-engine-combinations, where the 
propeller is directly fixed at the engine flange.
    Clutches, transmission shafts, intermediate bearings, angular 
drives (gearboxes), universal joints, shifting sleeves etc. are 
accommodated for neither by JAR-22, nor by part 23 (JAR-23), or part 
33 (JAR-E).
    The necessity to supplement/amend the Airworthiness Requirements 
became obvious for a powered sailplane, where a transmission shaft 
from the engine in the middle of the fuselage runs through the 
cockpit between the pilots (side-by-side seats) to the bow of the 
fuselage where the propeller is mounted.
    The rupture of a so installed transmission shaft can, besides 
the loss of thrust, also by the whirling of the parts that remain 
attached to the run-away engine have catastrophic effects to pilots 
and aircrafts/aeroplanes.
    Also differently arranged transmission shafts that do not pass 
through the cockpit can endanger the surrounding primary structure, 
the controls or other important systems critically.
    For transmission shaft installations the following Special 
Requirements have to be applied for powered sailplanes and aircraft 
(aeroplanes) in addition to JAR-22 and part 23 (JAR-23), 
respectively part 33 (JAR-E):
    (l) All parts between engine and propeller, that serve the 
transfer of engine-power to the propeller are regarded as parts of 
the engine and are, as far as practicable/applicable, to be shown to 
comply with JAR-22 Subpart H Engines or part 33 Aircraft Engines 
(JAR-E), respectively.
    (2) Propeller thrust, lateral loads and gyroscopic moments have 
to be transferred to load carrying members on the shortest possible 
way.
    (3) Dissimilar expansion/deformation between structural and 
powerplant parts, may it be under loads or/and temperatures has to 
be accounted for by appropriate means.
    (4) Universal joints used in the transmission shaft installation 
have to be selected and arranged/installed so that an unsteadiness 
of the rotation speed is avoided.

[[Page 16935]]

    (5) Wrappings, guidances, protective covers and all other 
structural members must have such a spacing from rotating parts, 
that under deformation due to flight or ground loads and if pressure 
is exerted by parts of the body (pilot or passenger) a radial or 
respectively longitudinal distance of at least 13 mm (0.5 inch) 
remains.
    (6) It has to be guaranteed that parts made of fibre-reinforced 
materials during operation do not exceed (reach) the softening 
temperature. Softening temperature: TGA according to DIN 29971. 
Compliance has to be sought in a ``cooling test flight'' according 
to JAR 22.1041/22.1047 or part 23, Sec. Sec.  23.1041/23.1045/
23.1047 (or JAR 23...), respectively.
    If the difference between the corrected maximum operational 
temperature and the softening temperature is less than 15, the 
operational temperature has to be monitored (continuously) by an 
instrument.
    (7) If parts of the transmission shaft installation are made 
from material not being fireproof, these parts have to be protected 
against the effects of fire in the engine compartment.
    (8) It has to be shown, that the whirling rest of a broken 
transmission shaft, still driven by the engine does neither directly 
endanger occupants (pilots included) nor parts of the primary 
structure in a way that the flight cannot be brought to a safe end. 
Compliance has to be sought in a test under the assumption that the 
shaft is broken at a place most critical for compliance and the 
engine running at take-off power.
    (9) The repeated in-flight-stopping and re-starting of the 
engine is common practice for powered sailplane. To avoid passing 
through a critical RPM-range, transmission shaft installation must 
operate in a sub-critical RPM-range.
    The critical RPM of any transmission shaft must be at least 1.5 
times the maximum operational RPM. When determining the critical RPM 
the influences of the maximum imbalance to be expected from the 
manufacturing process, as well as the bending of the shaft under 
load factor and probable forced bending by fuselage deformation has 
to be considered.
    (10) The vibration test required by JAR-22.1843 or FAR 33.43 
(a)(b)/ (JAR-E) respectively must comprise the complete transmission 
shaft installation (engine-transmission-shaft-propeller). The 
effects of engine stopping and restarting must be investigated.
    The stresses derived from the test above have to be superimposed 
with the stresses directly originating from load factors acting on 
the transmission shaft or are forced on the transmission shaft by 
deformation of the airframe.
    The resulting peak stresses must not exceed the fatigue limit of 
the material used for the transmission shaft installation.

Figure 2: LBA Document

    (20) E-2 LBA, Equivalent Safety Finding; LFLS Sec.  1167(d), 
Vectored Thrust Components [Auxiliary Thrust Vectoring].

Discussion

    LFLS Sec.  1167(d) (subpart E) requires an auxiliary means be 
provided to return the vectoring thrust system into a normal operating 
position should the primary means fail. The current design does not 
include this design feature. The LZ N07 is equipped with a system of 
swiveling propellers. This system is used for conventional cruise 
flight with the propellers in a vertical position and also for steering 
the airship at low airspeeds with the propellers in swiveled positions. 
This results in no one ``normal position'' of the propeller than can be 
specified. Even if the propeller swiveling system fails, such a stuck 
position might be useful for the pilot. Also, since all three engines 
are operating individually, a single vectoring failure does not 
interfere with the two remaining propulsion units.
    Instead of providing auxiliary means to return the system to the 
normal operating position, the design, operation, and function of the 
vectoring system on the Zeppelin LZ N07 airship provides an equivalent 
level of safety.
    To satisfy the provisions of LFLS Sec.  1167(d), the following is 
required:
    It will be shown by flight test that continued safe flight and 
landing is possible with a propeller stuck in any one position with the 
affected engine (still) running or shut off.
    (21) F-1 LBA, Additional Requirements; LFLS Sec.  1301, Function 
and Installation; and LFLS Sec.  1309, Equipment, Systems and 
Installations (HIRF).

Discussion

    The LZ N07 utilizes new avionics/electronic systems that provide 
critical data to the flight crew. The applicable regulations do not 
contain adequate or appropriate safety standards for the protection of 
these systems from the effects of high intensity radiated fields 
(HIRF). The LBA's required additional safety standards considered 
necessary to establish a level of safety equivalent to that established 
by existing airworthiness standards.
    There is no specific regulation that addresses protection 
requirements for electrical and electronic systems from HIRF. Increased 
power levels from the ground based radio transmitters and the growing 
use of sensitive electrical and electronic systems to command and 
control the airship, especially under IFR conditions, have made it 
necessary to provide adequate protection. To ensure that the level of 
safety is achieved equivalent to that intended by the regulations 
incorporated by reference, additional requirements are needed for the 
LZ N07 to require that new technology electrical and electronic systems 
be designed and installed to preclude component damage and interruption 
of critical functions due to effect of HIRF.

High Intensity Radiated Fields (HIRF)

    With the trend toward increased power levels from ground-based 
transmitters, plus the advent of space and satellite communications, 
coupled with electrical and electronic command and control of an 
airship, the immunity of critical systems to HIRF must be established. 
It is not possible to precisely define the HIRF to which the airship 
will be exposed in service. There is also uncertainty concerning the 
effectiveness of gondola shielding for HIRF. Furthermore, coupling of 
electromagnetic energy to gondola-installed equipment through the 
windows apertures is undefined. Based on surveys and analysis of 
existing HIRF emitters, an adequate level of protection exists when 
compliance with the HIRF special condition is shown.
    To satisfy the provisions of LFLS Sec.  1301 and LFLS Sec.  1309 
the following is required:
    The airship systems and associated components, considered 
separately and in relation to other systems, must be designed and 
installed so that:
    (a) Each system that performs a critical or essential function is 
not adversely affected when the airship is exposed to the normal HIRF 
environment.
    (b) All critical functions must not be adversely affected when the 
airship is exposed to the certification HIRF environment.
    (c) After the airship is exposed to the certification HIRF 
environment, each affected system that performs a critical function 
recovers normal operation without requiring any crew action, unless 
this conflicts with other operational or functional requirements of 
that system.
    The following definitions apply:
    (a) Critical function: A function whose failure would prevent 
continued safe flight and landing of the airship.
    (b) Essential function: A function whose failure would reduce the 
capability of the airship or the ability of the crew to cope with 
adverse operating conditions.
    (c) The definitions of normal and certification HIRF environments, 
frequency bands, and corresponding average and peak levels are defined 
in Table 4 and Table 5.

[[Page 16936]]

General Guidance Material
    The User Guide for AC/AMJ 20-1317 THE CERTIFICATION OF AIRCRAFT 
ELECTRICAL AND ELECTRONICAL SYSTEMS FOR OPERATION IN THE HIGH RADIATED 
FIELDS (HIRF) ENVIRONMENT dated 9/21/98 must be used. In case of 
conflicting issues, this notice will supersede, unless otherwise 
notified.

Criticality Definitions

    In order to perform hazard assessments, the table below defines 
equivalence:

                                 Table 4
------------------------------------------------------------------------
                               Guidance according    LFLS certification
   Definition CRI F-1/HIRF      to AC/AMJ 20-1317          basis *
------------------------------------------------------------------------
Critical....................  Catastrophic........  Multiple failure
                                                     analysis will not
                                                     apply in general.
Essential...................  Hazardous Severe      Multiple failure
                               Major.                analysis will not
                                                     apply in general.
------------------------------------------------------------------------
* Since the LFLS is based on 14 CFR part 23, multiple failure analysis
  will not apply in general. However, common mode failures, or failures
  if one failure would lead inevitably to another failure, have to be
  considered.

Equipment Test Requirements

    If ZLT can demonstrate for Level A, B, or C equipment that 
equipment testing is adequate for showing compliance, the following 
equipment test requirement will be used:
    RTCA DO-160 D, if equipment development was launched in 1996 or 
later a no TSO or JTSO certification will be obtained by the supplier.
    RTCA DO-160 C, or earlier if equipment development was launched in 
1995 or earlier, or if the equipment affected already holds a separate 
TSO or JZSO certification.

                                 Table 5
------------------------------------------------------------------------
                     Frequency                         Peak     Average
------------------------------------------------------------------------
10 kHz-100 kHz....................................         40         40
100 kHz-500 kHz...................................         40         40
500 kHz-2 MHz.....................................         40         40
2 MHz-30 MHz......................................        100        100
30 MHz-70 MHz.....................................         20         20
70 MHz-100 MHz....................................         20         20
100 MHz-200 MHz...................................         50         30
200 MHz-400 MHz...................................         70         70
400 MHz-700 MHz...................................        730         30
700 MHz-1 GHz.....................................       1300         70
1 GHz-2 GHz.......................................       2500        160
2 GHz-4 GHz.......................................       3500        240
4 GHz-6 GHz.......................................       3200        280
6 GHz-8 GHz.......................................        800        330
8 GHz-12 GHz......................................       3500        330
12 GHz-18 GHz.....................................       1700        180
------------------------------------------------------------------------

Certification HIRF Environment
    Field Strengths in Volts/Meter, (V/m).

    Note: At 10 kHz-100kHz a Height Impedance Field of 320V/m peak 
exists.


                                 Table 6
------------------------------------------------------------------------
                     Frequency                         Peak     Average
------------------------------------------------------------------------
10 kHz-100 kHz....................................         20         20
100 kHz-500 kHz...................................         20         20
500 kHz-2 MHz.....................................         30         30
2 MHz-30 MHz......................................         50         50
30 MHz-70 MHz.....................................         10         10
70 MHz-100 MHz....................................         10         10
100 MHz-200 MHz...................................         30         30
200 MHz-400 MHz...................................         25         25
400 MHz-700 MHz...................................        730         30
700 MHz-1 GHz.....................................         40         10
1 GHz-2 GHz.......................................       1700        160
2 GHz-4 GHz.......................................       3000        170
4 GHz-6 GHz.......................................       2300        280
6 GHz-8 GHz.......................................        530        230
------------------------------------------------------------------------

Normal HIRF Environment
    Field Strengths in Volts/Meter, (V/m).
Abbreviations:
GHz Gigahertz
IFR Instrument Flight Rules
kHz Kilohertz
m Meter
MHz Megahertz
V Volt
    (22) F-2 LBA, Additional Requirements; LFLS Sec.  1301, Function 
and Installation, and LFLS Sec.  1309, Equipment, Systems and 
Installations [Software development and transition to RTCA DO-178B/ED-
12B].

Discussion

    The LZ N07 will be certificated with microprocessor-based systems 
installed that contain software. The LBA considered that there was 
limited policy or guidance for transitioning to the use of RTCA DO 
178B/ED-12B from earlier guidance regarding means of compliance for 
software-based systems. Specific transition criteria were specified for 
the LZ N07 compliance program.
    RTCA DO 178B/ED-12B, ``Software Considerations in Airborne Systems 
and Equipment Certification,'' dated December 1, 1992, provides 
guidance for software development where industry and regulatory 
experience showed RTCA document DO 178A/ED-12A, ``Software 
Considerations in Airborne Systems and Equipment Certification,'' dated 
1985, required revision. Through RTCA, Inc./EUROCAE, a joint committee 
comprised of representatives from both the public and private sectors, 
created DO 178B/ED-12B to reflect the experience gained in the 
certification of aircraft and engines containing software based systems 
and equipment and to provide guidance in the area not previously 
addressed by DO 178A/ED-12A. DO 178B/ED-12B contains more objectively 
determinable compliance criteria and considerably enhances the 
consistency of software evaluations. The use of DO 178B/ED-12B provides 
for a more thorough and sure compliance finding to objective standards, 
reducing the likelihood of software errors.
    Due to being superseded for the reasons discussed above, DO 178A/
ED-12A and prior versions were not recognized by the LBA as acceptable 
means of compliance for software being developed or being modified for 
an airship certification program (in Germany) whose application date 
was later than January 11, 1993 (except as noted in subparagraph 1(a) 
and 1(b) below). The LZ N07 program fell into this category. ZLT was 
allowed to propose exceptions to the use of DO 178B/ED-12B (or 
equivalently acceptable means of compliance) for specific systems or 
equipment. These requests were evaluated on a case-by-case basis and 
were considered when:
    (a) The LBA determined that the software modification is so simple 
or straightforward that an upgrade of the applicant's processes to DO 
178B/ED-12B from earlier revisions of DO 178/ED-12 is not necessary for 
assuring that the modification is specified, designed, and implemented 
correctly, and verified appropriately; or
    (b) Where a straightforward and readily obvious determination could 
be made by the LBA that airworthiness will not be affected if some 
specific objectives of DO 178B/ED-12B were not met.
    One example might be the modification of a code table or local or 
private data that can be readily verified by inspection. A second 
example might

[[Page 16937]]

be minor gain changes necessary for adoption of existing equipment to a 
new airframe. A third example might be the modification of a small 
percentage of code that has no effect on common or global data or other 
forms of coupling between modules nor interfaces with other equipment 
or where such effects are easily limited and where such limiting is 
easily verifiable. A fourth example might be where a non-essential 
system with Level 3 software per DO 178A/ED-12A would be appropriately 
re-categorized during the system safety assessment and DO 178B/ED-12B 
processes as Level E software. Exemptions such as the above were, for 
the most part, directed at previously approved software-based equipment 
that had an established and acceptable service history performing the 
same function in the same installation environment as the new 
application and for which only significant changes were being made such 
as outlined above.
    Regardless of which version of DO 178/ED-12 was used, ZLT was 
required to submit to the LBA a Plan for Software Aspects of 
Certification (PSAC), a Software Configuration Index (SCI), and a 
Software Accomplishment Summary (SAS) containing the information 
specified in DO 178B/ED-12B, paragraphs 11.1, 11.16, and 11.20, 
respectively, in addition to any other information required by the 
version of DO 178/ED-12 used for the software approval.
    For the software being modified, two acceptable methods of 
upgrading to DO 178B/ED-12B were specified:
    (a) ZLT was allowed to upgrade the entire development baseline, 
including all processes and all data items per the provisions of DO 
178B/ED-12B, section 12.1.4. Existing processes and data items that can 
be shown to already meet the objectives for DO 178B/ED-12B will not 
need upgrading.
    (b) Alternatively, ZLT was allowed to choose an incremental 
approach, using DO 178B/ED-12B processes to make modifications and 
upgrading the products (data items) of the life cycle processes only 
where they are affected by the modification. A regression analysis 
should identify those areas of the code and other data items affected 
by the modification. Data items were upgraded in those areas where they 
were directly affected by the modification (for instance, new 
requirements) and where required in order to satisfy the objectives of 
DO 178B/ED-12B, Annex A (for instance, where otherwise unmodified 
requirements must be upgraded to provide sufficient data for the 
requirements-based testing of the modified code sections).
    In planning the transition activities using either alternative, ZLT 
should perform an analysis to see where the processes and products of 
the software life cycle do not satisfy the DO 178B/ED-12B objectives. 
This will provide a limit to the activity required and criteria for 
assessing the upgrade.
    To satisfy the provisions of LFLS Sec.  1301 and LFLS Sec.  1309, 
the following is required:
    Software development for the LZ N07 will be accomplished according 
to DO 178B/ED-12B (or equivalently acceptable means of compliance) for 
specific systems or equipment. Deviations from this requirement will be 
considered when:
    (a) The software modification is so simple or straightforward that 
an upgrade of the applicant's processes to DO 178B/ED-12B from earlier 
revisions of DO 178/ED-12 is not necessary for assuring that the 
modification is specified, designed, and implemented correctly, and 
verified appropriately; or
    (b) Where a straightforward and readily obvious determination can 
be made by the certifying authority that airworthiness will not be 
affected if some specific objectives of DO 178B/ED-12B were not met.
    The applicant will submit a Plan for Software Aspects of 
Certification (PSAC), a Software Configuration Index (SCI), and a 
Software Accomplishment Summary (SAS) containing the information 
specified in DO 178B/ED-12B, paragraphs 11.1, 11.16, and 11.20, 
respectively, in addition to any other information required by the 
version of DO 178/ED-12 used for the software approval.
    For software modifications, two methods of upgrading to DO 178B/ED-
12B are acceptable:
    (a) Upgrade the entire development baseline, including all 
processes and all data items, per the provisions of DO 178B/ED-12B, 
section 12.1.4. Existing processes and data items that can be shown to 
already meet the objectives for DO 178B/ED-12B will not need upgrading.
    (b) Choose an incremental approach, using DO 178B/ED-12B processes 
to make modifications and upgrading the products (data items) of the 
life cycle processes only where they are affected by the modification. 
A regression analysis should identify those areas of the code and other 
data items affected by the modification. Data items were upgraded in 
those areas where they were directly affected by the modification (for 
instance, new requirements), and where required in order to satisfy the 
objectives of DO 178B/ED-12B, Annex A (for instance, where otherwise 
unmodified requirements must be upgraded to provide sufficient data for 
the requirements-based testing of the modified code sections).
    In planning the transition activities using either alternative, an 
analysis will be performed to determine where the processes and 
products of the software life cycle do not satisfy the DO 178B/ED-12B 
objectives.
    Equipment comprising software that is already certified under TSO, 
JTSO, FAA-STC, or LBA requirements, will be excluded from this 
requirement. However, the software qualification standard of such 
equipment will be at least according to DO 178A.
    Equipment comprising software that is specifically developed for 
use in LZ N07 and modifications to equipment comprising software 
specific for LZ N07 that is not, or is not yet, certified under TSO, 
JTSO, FAA-STC, or LBA requirement, will be certified according to this 
requirement.
    (23) F-3 LBA, Additional Requirements, LFLS Sec.  1301, Function 
and Installation, and LFLS Sec.  1309, Equipment, Systems and 
Installations [Electronic Hardware Design Assurance (ASIC)].

Discussion

    The LZ N07 will utilize electronic systems that may perform 
critical and essential functions. During its certification of the 
airship, the LBA made the determination that LBA airworthiness 
requirements did not contain adequate standards or guidance for the 
assurance that the internal hardware of these electronic systems are 
designed to meet the appropriate safety standards.
    There was no existing LBA policy or guidance for showing compliance 
to the existing rules for those aspects of certification associated 
with Application Specific Integrated Circuits (ASICs) and Electronic 
Programmed Logic Devices (EPLDs). Recently, EUROCAE Working Group 46 
``Complex Electronic Hardware'' was established to work in cooperation 
with RTCA SC-180 to consider this subject.
    LFLS Sec.  1309 was intended by the LBA as a general requirement 
that should be applied to all systems and powerplant installations (as 
required by LFLS Sec.  901(a)) to determine the effect on the airship 
of a functional failure or malfunction. It is based on the principle 
that there should be an inverse relationship between the severity of 
the effect of a failure and the probability of its occurrence.

[[Page 16938]]

Definitions
    a. Continued Safe Flight and Landing: The capability for continued 
controlled flight and landing, possibly using emergency procedures, but 
without requiring exceptional pilot skill or strength. Some airship 
damage may be associated with a Failure Condition, during flight or 
upon landing.
    b. Error: An occurrence arising as a result of incorrect action by 
the flight crew or maintenance personnel.
    c. Event: An occurrence that has its origin distinct from the 
airship, such as atmospheric conditions (e.g., gusts, temperature 
variations, icing, and lightning strikes) runway conditions, cabin and 
baggage fires. The term is not intended to cover sabotage.
    d. Failure: A loss of function, or a malfunction, of a system or 
part thereof. e. Failure Condition: The effect on the Airship and its 
occupants, both direct and consequential, caused or contributed to by 
one or more failures, considering relevant adverse operational or 
environmental conditions. Failure Conditions may be classified 
according to their severities as follows:
    (1) Minor: Failure Conditions that would not significantly reduce 
Airship safety and which involve crew actions that are well within 
their capabilities. Minor failure conditions may include, for example, 
a slight reduction in safety margins or functional capabilities, a 
slight increase in crew workload, such as routine flight plan changes, 
or some inconvenience to occupants.
    (2) Major: Failure Conditions that would reduce the capability of 
the Airship or the ability of the crew to cope with adverse operating 
conditions to the extent that there would be, for example, a 
significant reduction in safety margins or functional capabilities, a 
significant increase in crew workload or in conditions impairing crew 
efficiency, or discomfort to occupants, possibly including injuries.
    (3) Hazardous: Failure conditions that would reduce the capability 
of the airship or the ability of the crew to cope with adverse 
operating conditions to the extent that there would be:
    (a) A large reduction in safety margins or functional capabilities;
    (b) Physical distress or higher workload such that the flight crew 
cannot be relied upon to perform their tasks accurately or completely; 
or
    (c) Serious or fatal injury to a relatively small number of the 
occupants.
    (4) Catastrophic: Failure conditions that would prevent Continued 
Safe Flight and Landing.
f. Redundancy: The presence of more than one independent means for 
accomplishing a given function or flight operation. Each means need not 
necessarily be identical.

Technical Discussion

    LFLS Sec.  1309(b) and (d) require substantiation by analysis and, 
where necessary, by appropriate ground, flight, or simulator tests, 
that a logical and acceptable inverse relationship exists between the 
probability and the severity of each Failure Condition. However, tests 
are not required to verify Failure Conditions that are postulated to be 
Catastrophic. The goal is to ensure an acceptable overall Airship 
safety level, considering all Failure Conditions of all systems.
    a. The requirements of LFLS Sec.  1309(b) and (d) are intended to 
ensure an orderly and thorough evaluation of the effects on safety of 
foreseeable failures or other events, such as errors or external 
circumstances, separately or in combination, involving one or more 
system functions. The interactions of these factors within a system and 
among relevant systems should be considered.
    b. The severities of Failure Conditions may be evaluated according 
to the following considerations:
    (1) Effects on the Airship, such as reductions in safety margins, 
degradations in performance, loss of capability to conduct certain 
flight operations, or potential or consequential effects on structural 
integrity.
    (2) Effects on crewmembers, such as increases above their normal 
workload that would affect their ability to cope with adverse 
operational or environmental conditions.
    (3) Effects on the occupants; i.e., passengers and crewmembers.
    (4) For convenience in conducting design assessments, Failure 
Conditions may be classified according to their severities as Minor, 
Major, Hazardous, or Catastrophic. Chapter 1, ``Definitions'' provides 
accepted definitions of these terms.
    (a) The classification of Failure Conditions does not depend on 
whether or not a system or function is the subject of a specific 
requirement. Some ``required'' systems, such as transponders, position 
lights, and public address systems, may have the potential for only 
Minor Failure Conditions. Conversely, other systems that are not 
``required,'' such as flight management systems, may have the potential 
for Major, Hazardous, or Catastrophic Failure Conditions.
    (b) Regardless of the types of assessment used, the classification 
of Failure Conditions should always be accomplished with consideration 
of all relevant factors; e.g., system, crew, performance, operational, 
external, etc. Examples of factors would include the nature of the 
failure modes, any effects or limitations on performance, and any 
required or likely crew action. It is particularly important to 
consider factors that would alleviate or intensify the severity of a 
Failure Condition. An example of an alleviating factor would be the 
continued performance of identical or operationally similar functions 
by other systems not affected by the Failure Condition. Examples of 
intensifying factors would include unrelated conditions that would 
reduce the ability of the crew to cope with a Failure Condition, such 
as weather or other adverse operational or environmental conditions.
    The probability that a Failure Condition would occur may be 
assessed as Probable, Improbable (Remote or Extremely Remote), or 
Extremely Improbable. Each Failure Condition should have a probability 
that is inversely related to its severity.
    1. Minor Failure Conditions may be Probable.
    2. Major Failure Conditions must be no more frequent than 
Improbable (Remote).
    3. Hazardous Failure Conditions must be no more frequent than 
Improbable (Extremely Remote).
    4. Catastrophic Failure Conditions must be Extremely Improbable.
    c. An assessment to identify and classify Failure Conditions is 
necessarily qualitative. On the other hand, an assessment of the 
probability of a Failure Condition may be either qualitative or 
quantitative. An analysis may range from a simple report that 
interprets test results or compares two similar systems to a detailed 
analysis that may (or may not) include estimated numerical 
probabilities. The depth and scope of an analysis depends on the types 
of functions performed by the system, the severities of Failure 
Conditions, and whether or not the system is complex. Regardless of its 
type, an analysis should show that the system and its installation can 
tolerate failures to the extent that Major and Hazardous Failure 
Conditions are Improbable and Catastrophic Failure Conditions are 
Extremely Improbable:
    (1) Experienced engineering and operational judgment should be 
applied when determining whether or not a system is complex. Comparison 
with similar, previously approved systems is sometimes helpful. All 
relevant systems Attributes should be considered; however, the 
complexity of the software used to program a digital-computer-

[[Page 16939]]

based system should not be considered because the software is assessed 
and controlled by other means, as described in paragraph 2.i.
    (2) An analysis should consider the application of the fail-safe 
design concept described in paragraph 5 and give special attention to 
ensuring the effective use of design techniques that would prevent 
single failures or other events from damaging or otherwise adversely 
affecting more than one redundant system channel or more than one 
system performing operationally-similar functions. When considering 
such common-cause failures or other events, consequential or cascading 
effects should be taken into account if they would be inevitable or 
reasonably likely.
    (3) Some examples of such potential common-cause failures or other 
events would include rapid release of energy from concentrated sources 
such as uncontained failures of rotating parts or pressure vessels, 
pressure differentials, non-catastrophic structural failures, loss of 
environmental conditioning, disconnection of more than one subsystem or 
component by over temperature protection devices, contamination by 
fluids, damage from localized fires, loss of power, excessive voltage, 
physical or environmental interactions among parts, human or machine 
errors, or events external to the system or to the Airship.
    d. Compliance for a system or part thereof that is not complex may 
sometimes be shown by design and installation appraisals and evidence 
of satisfactory service experience on other Airships using the same or 
other systems that are similar in their relevant Attributes.
    e. In general, a Failure Condition resulting from a single failure 
mode of a device cannot be accepted as being Extremely Improbable. In 
very unusual cases, however, experienced engineering judgment may 
enable an assessment that such a failure mode is not a practical 
possibility. When making such an assessment, all possible and relevant 
considerations should be taken into account, including all relevant 
Attributes of the device. Service experience showing that the failure 
mode has not yet occurred may be extensive, but it can never be enough. 
Furthermore, flight crew or ground crew checks have no value if a 
Catastrophic failure mode would occur suddenly and without any prior 
indication or warning. The assessment's logic and rationale should be 
so straightforward and readily obvious that, from a realistic and 
practical viewpoint, any knowledgeable, experienced person would 
unequivocally conclude that the failure mode simply would not occur.
    f. LFLS Sec.  1309(c) provides requirements for system monitoring, 
failure warning, and capability for appropriate corrective crew action. 
Guidance on acceptance means of compliance is provided in paragraph 
8.g.
    g. In general, the means of compliance described in this Appendix 
to CRI F-ASIC's are not directly applicable to software assessments 
because it is not feasible to assess the number or kinds of software 
errors, if any, that may remain after the completion of system design, 
development, and test. RTCA DO-178A and EUROCAE ED-12A, or later 
revisions thereto, provide acceptable means for assessing and 
controlling the software used to program digital-computer-based 
systems. The documents define and use certain terms to classify the 
criticalities of functions. These terms have the following 
relationships to the terms used in this Appendix to CRI F-ASIC's to 
classify Failure Conditions: Failure Conditions adversely affecting 
non-essential functions would be Minor, Failure Conditions adversely 
affecting essential functions would be Major or Hazardous, and Failure 
Conditions adversely affecting critical functions would be 
Catastrophic.
    h. Functional Hazard Assessment.
    Before an applicant proceeds with a detailed safety assessment, it 
is useful to prepare a preliminary hazard assessment of the system 
functions in order to determine the need for and scope of subsequent 
analysis. This assessment may be conducted using service experience, 
engineering and operational judgment, or a top-down deductive 
qualitative examination of each function performed by the system. A 
functional hazard assessment is a systematic, comprehensive examination 
of a system's functions to identify potential Major, Hazardous and 
Catastrophic Failure Conditions that the system can cause or contribute 
to not only if it malfunctions or fails to function but also in its 
normal response to unusual or abnormal external factors. It is 
concerned with the operational vulnerabilities of the system rather 
than with the detailed hardware analysis.
    Each system function should also be examined with respect to 
functions performed by other Airship systems because the loss of 
different but related functions provided by separate systems may affect 
the severity of Failure Conditions postulated for a particular system. 
In assessing the effects of a Failure Condition, factors that might 
alleviate or intensify the direct effects of the initial Failure 
Condition should be considered, including consequent or related 
conditions existing within the Airship that may affect the ability of 
the crew to deal with direct effects, such as the presence of smoke, 
acceleration vectors, interruption of communication, interference with 
cabin pressurization, etc.
    When assessing the consequences of a given Failure Condition, 
account should be taken of the warnings given, the complexity of the 
crew action, and the relevant crew training. The number of overall 
Failure Conditions involving other than instinctive crew actions may 
influence the flight crew performance that can be expected. Training 
requirements may need to be specified in some cases.
    A functional hazard assessment may contain a high level of detail 
in some cases, such as for a flight guidance and control system with 
many functional modes, but many installations may need only a simple 
review of the system design by the applicant. The functional hazard 
assessment is a preliminary engineering tool. It should be used to 
identify design precautions necessary to ensure independence, to 
determine the required software level, and to avoid common mode and 
cascade failures.
    If further safety analysis is not provided, then the functional 
hazard assessment could itself be used as certification documentation.
    (1) Analysis of Hazardous and Catastrophic Failure Conditions
    (a) A detailed safety analysis will be necessary for each Hazardous 
and Catastrophic Failure Condition identified by the functional hazard 
assessment. Hazardous Failure Conditions should be Improbable 
(Extremely Remote), and Catastrophic Failure Conditions should be 
Extremely Improbable. The analysis will usually be a combination of 
qualitative and quantitative assessment of the design. Probability 
levels that are related to Catastrophic Failure Conditions should not 
be assessed only on a numerical basis, unless this basis can be 
substantiated beyond reasonable doubt.
    (b) For simple and conventional installations, i.e., low complexity 
and similarity in relevant Attributes, it may be possible to assess a 
Catastrophic Failure Condition as being Extremely Improbable on the 
basis of experienced engineering judgment, without using all the formal 
procedures listed above. The basis for the assessment will be the 
degree of redundancy, the established independence and isolation of the 
channels and the reliability record of the technology involved. A 
Failure Condition resulting from a single failure

[[Page 16940]]

mode of a device cannot generally be accepted as being Extremely 
Improbable, except in very unusual cases.
    To satisfy the provisions of LFLS Sec.  1301 and LFLS Sec.  1309 
Equipment, Systems and Installations with respect to Electronic 
Hardware Design Assurance (ASIC), the design considerations and 
analyses described in the above Discussion and Technical Discussion 
will be utilized to accomplish the following:
    Correct operation will be demonstrated by test or analysis under 
all combinations and permutations of conditions of the gates within the 
device for electronic hardware whose anomalous behavior would cause or 
contribute to a failure of a system resulting in a catastrophic or 
hazardous failure condition for the airplane as defined in Advisory 
Circular 23.1309-1C.
    Correct operation will also be demonstrated by test or analysis 
under all combinations and permutations of conditions at the pins of 
the device for electronic hardware whose anomalous behavior would cause 
or contribute to a failure of a system resulting in a major or minor 
failure condition for the airplane as defined in Advisory Circular 
23.1309-1C.
    If the testing and analysis methods outlined above are impractical 
due to the complexity of the device, the electronic hardware should be 
developed using a structured development process. The applicant may use 
the guidelines in RTCA DO-254, ``Design Assurance Guidance for Airborne 
Electronic Hardware'' or another process that is acceptable to the FAA. 
If the applicant chooses to use the guidelines in RTCA DO-254, the 
hardware development assurance levels should be the same as the 
software development assurance levels agreed to by the applicant and 
the FAA.
    (24) F-4 LBA, Additional Requirements concerning LFLS Sec.  1301, 
Sec.  1303, Sec.  1305, Sec.  1309, Sec.  1321, Sec.  1322, Sec.  1330, 
Sec.  1431 with respect to Liquid Crystal Displays.

Discussion

    ZLT proposed to use Liquid Crystal Displays (LCDs) for presentation 
of Airspeed/Altitude/Attitude/Engine/Warning and Caution information to 
the pilots. The LBA had no published approval criteria for LCD 
technology.
    The LCDs to be installed in the LZ-N07 flight deck will display 
flight information, including functions critical to safe flight and 
landing. There is presently no existing guidance material for Liquid 
Crystal Display airworthiness certification in the LFLS. For the LZ-N07 
certification, the following Guidance Material for LCD airworthiness 
approval was developed. The following Guidance Material provides 
acceptable guidance for airworthiness approval of display systems using 
LCD technology in the LZ-N07.

Guidance Material

Guidance Material for Electronic Liquid Crystal Display Systems 
Airworthiness Approval

Purpose
    This Guidance Material provides guidance for certification of 
Liquid Crystal Display (LCD) based electronic display systems used for 
guidance, control, or decision-making by the pilots of an Airship. Like 
all guidance material, this document is not, in itself, mandatory and 
does not constitute a regulation. It is issued to provide guidance and 
to outline a method of compliance with the rules.
Scope
    The material provided in this section consists of guidance related 
to pilot displays and specifications for LCDs in the cockpit of an 
Airship. The content of the Appendix is limited to statements of 
general certification considerations, including color, symbology, 
coding, clutter, dimensionality, and attention-getting requirements, 
and display visual characteristics.
    a. Information Separation
    (1) Color Standardization
    (a) Although color standardization is desirable, during the initial 
certification of electronic displays, color standards for symbology 
were not imposed (except for cautions and warnings in LFLS Sec.  1322). 
At that time, the expertise did not exist within industry or the LBA, 
nor did sufficient service experience exist to rationally establish a 
suitable color standard.
    (b) In spite of the permissive LCD color atmosphere that existed at 
the time of initial LCD display certification programs, an analysis of 
the major certifications to date reveals many areas of common color 
design philosophy; however, if left unrestricted, in several years 
there will be few remaining common areas of color selection. If that is 
the case, information transfer problems may begin to occur that have 
significant safety implications. To preclude this, the following colors 
are being recommended based on current-day common usage. Deviations may 
be approved with acceptable justification.
    (c) The following depicts acceptable display colors related to 
their functional meaning recommended for electronic display systems.
    1. Display features should be color-coded as follows:

------------------------------------------------------------------------
 
------------------------------------------------------------------------
Warnings.................................  Red
Flight envelope and system limits........  Red
Cautions, abnormal sources...............  Amber/Yellow
Earth....................................  Tan/Brown
Engaged modes............................  Green
Sky......................................  Cyan/Blue
ILS deviation pointer....................  Magenta
Flight director bar......................  Magenta/Green
------------------------------------------------------------------------

    2. Specified display features should be allocated colors from one 
of the following color sets:

 
------------------------------------------------------------------------
                                     Color set 1         Color set 2
------------------------------------------------------------------------
Fixed reference symbols........  White.............  Yellow*
Current data, values...........  White.............  Green
Armed modes....................  White.............  Cyan
Selected data, values..........  Green.............  Cyan
Selected heading...............  Magenta**.........  Cyan
Active route/flight plan.......  Magenta...........  White
------------------------------------------------------------------------
*The extensive use of the color yellow for other than caution/abnormal
  information is discouraged.
**In color Set 1, magenta is intended to be associated with those
  analogue parameters that constitute ``fly to'' or ``keep centered''
  type information.


[[Page 16941]]

    (d) When deviating from any of the above symbol color assignments, 
the manufacturer should ensure that the chosen color set is not 
susceptible to confusion or color meaning transference problems due to 
dissimilarities with this standard. The Authority test pilot should be 
familiar with other systems in use and evaluate the system specifically 
for confusion in color meanings.
    (e) The LBA does not intend to limit electronic displays to the 
above colors, although they have been shown to work well. The colors 
available from a symbol generator/display unit combination should be 
carefully selected on the basis of their chrominance separation. 
Research studies indicate that regions of relatively high color 
confusion exist between red and magenta, magenta and purple, cyan and 
green, and yellow and orange (amber). Colors should track with 
brightness so that chrominance and relative chrominance separation are 
maintained as much as possible over day/night operation. Requiring the 
flight crew to discriminate between shades of the same color for symbol 
meaning in one display is not recommended.
    (f) Chrominance uniformity should be in accordance with the 
guidance provided in SAE Document ARP 1874. As designs are finalized, 
the manufacturer should review his color selections to ensure the 
presence of color works to the advantage of separating logical 
electronic display functions or separation of types of displayed data. 
Color meanings should be consistent throughout all color LCD displays 
in the cockpit. In the past, no criteria existed requiring similar 
color schemes for left and right side installations using electro-
mechanical instruments.
    (2) Color Perception versus Workload
    (a) When color displays are used, colors should be selected to 
minimize display interpretation workload. Symbol coloring should be 
related to the task or crew operation function. Improper color-coding 
increases response times for display item recognition and selection, 
and it increases the likelihood of errors in situations where response 
rate demands exceed response accuracy demands. Color assignments that 
differ from other displays in use, either electromechanical or 
electronic, or that differ from common usage (such as red, yellow, and 
green for stoplights), can potentially lead to confusion and 
information transferal problems.
    (b) When symbology is configured such that symbol characterization 
is not based on color contrast alone but on shape as well, then the 
color information is seen to add a desirable degree of redundancy to 
the displayed information. There are conditions in which pilots whose 
vision is color deficient can obtain waivers for medical qualifications 
under National crew license regulations. In addition, normal aging of 
the eye can reduce the ability to sharply focus on red objects or 
discriminate blue/green. For pilots with such deficiency, display 
interpretation workload may be unacceptably increased unless symbology 
is coded in more dimensions than color alone. Each symbol that needs 
separation because of the criticality of its information content should 
be identified by at least two distinctive coding parameters (size, 
shape, color, location, etc.).
    (c) Color diversity should be limited to as few colors as practical 
to ensure adequate color contrast between symbols. Color grouping of 
symbols, annunciations, and flags should follow a logical scheme. The 
contribution of color to information density should not make the 
display interpretation times so long that the pilot perceives a 
cluttered display.
    (3) Standard Symbology. Many elements of electronic display formats 
lend themselves to standardization of symbology, which would shorten 
training and transition times when pilots change airplane types.
    (4) Symbol Position
    (a) The position of a message or symbol within a display conveys 
meaning to the pilot. Without the consistent or repeatable location of 
a symbol in a specific area of the electronic display, interpretation 
errors and response times may increase. The following symbols and 
parameters should be position consistent:
    (1) All warning/caution/advisory annunciation locations.
    (2) All sensor data: altitude, airspeed, glideslope, etc.
    (3) All sensor failure flags. (Where appropriate, flags should 
appear in the area where the data is normally placed.)
    (4) Either the pointer or scale for analogue quantities should be 
fixed. (Moving scale indicators that have a fixed present value may 
have variable limit markings.)
    (b) An evaluation of the positions of the different types of 
alerting messages and annunciations available within the electronic 
display should be conducted, with particular attention given to 
differentiation of normal and abnormal indications. There should be no 
tendency to misinterpret or fail to discern a symbol, alert, or 
annunciation due to an abnormal indication being displayed in the 
position of a normal indication and having similar shape, size or 
color.
    (c) Pilot and copilot displays may have minor differences in 
format, but all such differences should be evaluated specifically to 
ensure that no potential for interpretation error exists when pilots 
make cross-side display comparisons.
    (5) Clutter. A cluttered display is one that uses an excessive 
number and/or variety of symbols, colors, or small spatial 
relationships. This causes increased processing time for display 
interpretation. One of the goals of display format design is to convey 
information in a simple fashion in order to reduce display 
interpretation time. A related issue is the amount of information 
presented to the pilot. As this increases, tasks become more difficult 
as secondary information may detract from the interpretation of 
information necessary for the primary task. A second goal of display 
format design is to determine what information the pilot actually 
requires in order to perform the task at hand. This will serve to limit 
the amount of information that needs to be presented at any point in 
time. Addition of information by pilot selection may be desirable, 
particularly in the case of navigational displays, as long as the basic 
display modes remain uncluttered after pilot de-selection of secondary 
data. Automatic de-selection of data has been allowed in the past to 
enhance the pilot's performance in certain emergency conditions.
    (6) Interpretation of Two-Dimensional Displays. Modern 
electromechanical attitude indicators are three-dimensional devices. 
Pointers overlay scales; the fixed airplane symbol overlays the flight 
director single cue bars that, in turn, overlay a moving background. 
The three-dimensional aspect of a display plays an important role in 
interpretation of instruments. Electronic flight instrument system 
displays represent an attempt to copy many aspects of conventional 
electromechanical displays but in only two dimensions. This can present 
a serious problem in quick-glance interpretation, especially for 
attitude. For displays using conventional, discrete symbology, the 
horizon line, single cue flight director symbol, and fixed airplane 
reference should have sufficient conspicuity such that the quick-glance 
interpretation should never be misleading for basic attitude. This 
conspicuity can be gained by ensuring that the outline of the fixed 
airplane symbol(s) always retains its distinctive shape, regardless of 
the background or position of the horizon line or pitch ladder. Color 
contrast is helpful in defining distinctive display elements but is 
insufficient by itself

[[Page 16942]]

because of the reduction of chrominance difference in high ambient 
light levels. The characteristics of the flight director symbol should 
not detract from the spatial relationship of the fixed airplane 
symbol(s) with the horizon. Careful attention should be given to the 
symbol priority (priority of displaying one symbol overlaying another 
symbol by editing out the secondary symbol) to assure the conspicuity 
and ease of interpretation similar to that available in three-
dimensional electromechanical displays.

    Note: Horizon lines and pitch scales that overwrite the fixed 
airplane symbol or roll pointer have been found unacceptable in the 
past.

    (7) Attention-Getting Requirements
    (a) Some electronic display functions are intended to alert the 
pilot to changes: navigation sensor status changes (VOR flag), computed 
data status changes (flight director flag or command cue removal), and 
flight control system normal mode changes (annunciator changes from 
armed to engaged) are a few examples. For the displayed information to 
be effective as an attention-getter, some easily noticeable change must 
be evident. A legend change by itself is inadequate to annunciate 
automatic or uncommanded mode changes. Color changes may seem adequate 
in low light levels or during laboratory demonstrations but become much 
less effective at high ambient light levels. Motion is an excellent 
attention-getting device. Symbol shape changes are also effective, such 
as placing a box around freshly changed information. Short-term 
flashing symbols (approximately 10 seconds or flash until acknowledge) 
are effective attention-getters. A permanent or long-term flashing 
symbol that is non-cancelable should not be used.
    (b) In some operations, continued operation with inoperative 
equipment is allowed (under provisions of an MEL). The display designer 
should consider the applicant's MEL desires because in some cases a 
continuous strong alert may be too distracting for continued dispatch.
    (8) Color Drive Failure. Following a single color drive failure, 
the remaining symbology should not present misleading information, 
although the display does not have to be usable. If the failure is 
obvious, it may be assumed that the pilot will not be susceptible to 
misleading information due to partial loss of symbology. To make this 
assumption valid, special cautions may have to be included in the AFM 
procedures that point out to the pilot that important information 
formed from a single primary color may be lost, such as red flags.
    (9) For Both Active Matrix and Segmented Liquid Crystal Displays
    Viewing Envelope: The installed display must meet all the following 
requirements when viewed from a rectangle centered on the design eye 
position and sized 1-foot vertical dimension and 2-feet horizontal 
dimension.
    General: The display symbology must be clearly readable throughout 
the viewing envelope under all ambient illumination levels ranging from 
1.1 lux (0.10 fc) to sun shaft illumination of 86,400 lux (8000 fc) at 
45 degrees incidence to the face of the display.
    Symbol Alignment: Symbols that are interpreted relative to each 
other must be aligned to preclude erroneous interpretation.
    Flicker: Flicker must not be readily discernible or distracting 
under day, twilight, or night conditions, considering both foveal and 
full peripheral vision, and using a format most susceptible to 
producing flicker.
    Multiple Images: Multiple display images produced by light not 
normal to the display surface must neither be distracting nor cause 
erroneous interpretation.
    Luminance: The display luminance must be sufficient to provide a 
comfortable level of viewing under all conditions and provide rapid eye 
adaptation when transitioning from looking outside the flight deck.
    Minimum Luminance: Under night lighting, with the display 
brightness set at the lowest usable level for flight with normal 
symbology, all flags and annunciators must be adequately visible.
    Lighting: In order to aid daylight viewing, the displays' 
backlighting must be designed such that adequate daylight backlighting 
is provided when the cockpit discrete lighting control is set to the 
`bright' position. In ``non-bright'' positions, the displays must be 
modulated in a balanced fashion in conjunction with other cockpit 
lighting.
    (10) For Active Matrix Displays
    Matrix Anomalies: For both static and dynamic formats, the display 
must have no matrix anomalies that cause distraction or erroneous 
interpretation.
    Line Width Uniformity: Lines of specified color and luminance must 
remain uniform in width at all orientations. Unintended line width 
variation must not be readily apparent or distracting in any case.
    Symbol Quality: Symbols must not have distracting gaps or geometric 
distortions that cause erroneous interpretations.
    Symbol Motion: Display symbology that is in motion must not have 
distracting or objectionable jitters, jerkiness, or ratcheting effects.
    Image Retention: Image retention must not be readily discernible 
day or night and must not be distracting or cause an erroneous 
interpretation or smearing effect for motion dynamic symbology.
    Defects: Visible defects on the display surface (such as ``on'' 
elements, ``off'' elements, spots, discolored areas, etc.) must not be 
distracting or cause an erroneous interpretation. Service limits for 
defects must be established.
    Luminance Uniformity: Display areas of a specified color and 
luminance must have a luminance uniformity of less than 50 percent 
across the utilized display surface. The rate of change of luminance 
within any small area shall be minimized to eliminate distracting 
visual effects. These requirements apply for any eye position within 
the display viewing envelope.
    Contrast Ratios: The average contrast ratio over the usable display 
surface must be a minimum of 201 at the design eye position and 101 for 
any eye position within the display viewing envelope when measured 
under a dark ambient illumination. This requirement is based on a 0.5 
mm (0.0201) line width. Smaller line widths must have a comparable 
readability, which may require a higher contrast ratio.
    (11) For Segmented Displays
    Activated Segments: Activated segments must have a contrast ratio 
with the immediately adjacent inactivated background of 21 for viewing 
angles of on-axis to 50 degrees off-axis.
    Inactivated Segments: When segments are not electrically activated, 
there must be no obtrusive difference between the normal background 
luminance, color, or texture and the inactivated segments of the area 
surrounding them. The contrast ratio between inactivated segments and 
the background must not be greater than 1.151 in a light ambient when 
viewed from an angle normal to the display up to an angle 50 degrees 
off-axis.
    For the purpose of this Issue Paper, the following definition 
applies:

Luminance Uniformity = (Lmax - Lmin / 
Lave (expressed in percent)

Where
Lmax = Maximum luminance measured anywhere on the 
utilized display surface
Lmin = Minimum luminance measured anywhere on the 
utilized display surface
Lave = Average luminance of the utilized display surface

    To satisfy the provisions of LFLS Sec.  1301, Sec.  1303, Sec.  
1305, Sec.  1309, Sec.  1321,

[[Page 16943]]

Sec.  1322, Sec.  1330, Sec.  1431 with respect to Liquid Crystal 
Displays, the design considerations and analyses described in the above 
Guidance Material will be utilized:
    (a) Equipment comprising LCDs that is not specifically developed 
for use in the LZ-N07, and which is already certified under TSO, JTSO, 
FAA-STC, or LBA Kennblatt, will be excluded and not certified according 
to these guidelines.
    (b) Equipment comprising LCDs that is specifically developed for 
the use in LZ-N07, and modifications to equipment comprising LCDs 
specific for the LZ-N07, and that is not, or not yet, certified under 
TSO, JTSO, FAA-STC, or LBA Kennblatt, will be certified according to 
these guidelines.
    (25) F-5 LBA, Additional Requirements; LFLS Sec.  1301, Function 
and Installation, and LFLS Sec.  1309, Equipment, Systems and 
Installations, Use of Commercial Off-The-Shelf (COTS) Software in 
Airship Avionics Systems.

General Discussion

    The LZ N07 will be certificated with digital microprocessor based 
systems installed that may contain commercial off-the-shelf (COTS) 
software. This Guidance Material identifies acceptable means of 
certifying airborne systems and equipment containing COTS software on 
the airship.

Background

    Many COTS software applications and components have been developed 
for use outside the field of commercial air transportation. Much of the 
COTS software has been developed for systems for which safety is not a 
concern or for systems with safety criteria different from that of 
commercial airships. Consequently, for COTS software, adequate 
artifacts may not be available to assess the adequacy of the software 
integrity. Available evidence may be insufficient to show that adequate 
software life cycle processes were used. RTCA DO 178B/ED-12B recognizes 
the above and addresses means by which COTS may be shown to comply with 
airship certification requirements.

Technical Discussion

    Document RTCA DO 178B/ED-12B provides a means for obtaining the 
approval of airborne COTS software. For those systems that make use of 
COTS software, the objectives of RTCA DO 178B/ED-12B should be 
satisfied. If deficiencies exist in the life cycle data of COTS 
software, DO 178B/ED-12B addresses means to augment that data to 
satisfy the objectives. If Zeppelin chooses to utilize a means other 
than DO 178B/ED-12B, the LBA requests Zeppelin to propose, via the Plan 
for Software Aspects of Certification (PSAC), how it intends to show 
that all COTS software complies with Airship Requirements LFLS 
Sec. Sec.  1301, 1309. Zeppelin should obtain agreement on the means of 
compliance from the LBA prior to implementation.

Abbreviations Used in this Guidance

                                 Table 7
------------------------------------------------------------------------
               Abbreviation                          Explanation
------------------------------------------------------------------------
COTS......................................  Commercial Off-the-Shelf
                                             Software
CRI.......................................  Certification Review Item
EUROCAE...................................  European Organization for
                                             Civil Aviation Electronics
LBA.......................................  Luftfahrt Bundesamt
LFLS......................................  Airworthiness Requirements
                                             for Airships
PSAC......................................  Plan for Software Aspects of
                                             Certification
RTCA......................................  Radio Technical Commission
                                             for Aeronautics
------------------------------------------------------------------------

    To satisfy the provisions of LFLS Sec.  1301, Function and 
Installation, and LFLS Sec.  1309, Equipment, Systems and 
Installations, Use of Commercial Off-the-Shelf (COTS) Software in 
Airship Avionics Systems the design considerations and analyses 
described in the above Guidance Material will be utilized:
    Equipment comprising COTS that is not specifically developed for 
use in the LZ-N07, and which is already certified under TSO, JTSO, FAA-
STC, or LBA Kennblatt, will be excluded and not certified according to 
this Guidance Material.
    Equipment comprising COTS that is specifically developed for use in 
the LZ-N07, and modifications to equipment comprising COTS specific for 
LZ-N07, and that is not, or not yet, certified under TSO, JTSO, FAA-
STC, or LBA Kennblatt, will be certified according to this Guidance 
Material.
    (26) F-6 LBA, Sec. Sec.  1301, 1322, 1528, 1585; LFLS (Equivalent 
Safety Finding) Envelope Pressure Indicator--Color Coding.

Discussion

    To indicate the envelope pressure of the LZ-N07, ZLT will propose 
an instrument (Envelope Pressure Indicator, EPI) that will provide 
annunciation of the Helium and Ballonet Pressure as well as indications 
of the aft and forward Fan and Sensor Fail status using LED columns. 
The measurement range covers a red, amber, and green band by a colored 
scale adjacent to the LED columns. The LED columns are continuously of 
an amber color, due to the technical solution possible only. In 
addition, any out-of-limit pressure determination will trigger a 
discrete warning output to the Integrated Instrument Display System 
(IIDS) for crew alerting and generation of an appropriate warning 
message.
    Using the pressure indications, the flight crew is able to monitor 
and control the airship throughout the flight. Furthermore, the ground 
crew will utilize the EPI to maintain constant pressures in the hull.
    Messages on displays should be unambiguous and easily readable and 
should be designed to avoid confusion to the crew. The use of an amber 
colored LED column, indicating possible red, amber, and green status of 
the associated systems, is not in line with the general color 
philosophy of the LZ N07 cockpit and the applicable LFLS requirements, 
and it was considered by the LBA as an unusual design feature.
    While the LBA allowed the use of amber based on an equivalent 
safety finding, we believe that the provisions of LFLS Sec.  1322, 
where an amber indication is reserved to indicate where immediate crew 
awareness is required and subsequent crew action will be required, 
should be adhered to.
    The control and indicating systems will, therefore, comply with the 
provisions of LFLS Sec.  1322.
    (27) F-7 LBA, Equivalent Safety Finding Sec.  1387(b) LFLS, Bow 
Light Dihedral Angle.

Discussion

    LFLS Sec.  1387(b) requires a dihedral angle formed by two 
intersecting vertical planes making angles of 110 degrees to the right 
and to the left. LFLS appendix table 10 requires, in addition, a 
minimum light intensity of 20 cd throughout the dihedral angle. The LZ-
N07 system only attains the required intensity over 100 degrees but is 
still visible from 100 degrees to 110 degrees (left and right) at a 
reduced intensity. The LBNA granted an equivalency to LFLS Sec.  
1387(b) based on the greater dihedral angle coverage of the aft light, 
+/-80 degrees rather than +/-70 degrees at the specified intensity. 
This is acceptable to the FAA.
    To satisfy the provisions of LFLS Sec.  1387(b), the following is 
required:
    The LFLS Sec.  1387(b) required dihedral angle will be no less than 
100 degrees at the intensities specified in Table 10 of the appendix of 
the LFLS. In addition, the rear light will have an included angle of +/
-80 degrees at the specified intensity from Table 10 of the appendix of 
the LFLS. Refer to Figure 3.

[[Page 16944]]

[GRAPHIC] [TIFF OMITTED] TN31MR08.001

    (28) Ballast Water.

Discussion

    To minimize the possibility of environmental contamination from 
ballast water, there will be provisions in the airship or servicing 
provisions that ensure that biological or chemical contamination does 
not occur due to the servicing of ballast water of one location and 
dumping of water in a different location. This provision will be added 
to the certification basis as a special environmental requirement:

    Under no circumstances may water ballast be loaded or released 
that does not comply with the provisions of 40 CFR part 141, 
National Primary Drinking Water Regulations. Obtaining water from a 
water supply use for human consumption is acceptable; water aerially 
released or otherwise dumped cannot degrade beyond the limits set by 
40 CFR part 141. If ballast water is contaminated, it can only be 
released into appropriate sewage facilities in accordance with 
national and local laws and regulations. These provisions will be 
explained in the Airship Flight Manual and ground operations 
materials and manuals. Procedures will also be developed that will 
eliminate the possibility of biological contamination growing in the 
ballast system and then being jettisoned or dumped, unless detected 
and treated.

    The ballast system will have a method of securing filler locations 
to eliminate the possibility of tampering with the system.

    Issued in Kansas City, Missouri, on March 21, 2008.
David R. Showers
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E8-6600 Filed 3-28-08; 8:45 am]
BILLING CODE 4910-13-P