[Federal Register Volume 60, Number 105 (Thursday, June 1, 1995)]
[Proposed Rules]
[Pages 28547-28550]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-13397]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-93; Special Conditions No. 25-ANM-99]
Special Condition: Cessna Aircraft Company, Model 750 (Citation
X) Airplane, High-Intensity Radiated Fields
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special condition.
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SUMMARY: This special condition for the Cessna Aircraft Company
(Cessna) is issued for the Model 750 (Citation X) airplane. This new
airplane will utilize new avionics/electronic systems that provide
critical data to the flightcrew. 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. This
special condition contains the additional safety standards that the
Administrator considers necessary to establish a level of safety
equivalent to that established by the existing airworthiness standards.
EFFECTIVE DATE: July 3, 1995.
FOR FURTHER INFORMATION CONTACT:
Mark Quam, FAA, Standardization Branch, ANM-113, Transport Airplane
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW.,
Renton, Washington, 98055-4056; telephone (206) 221-2145, facsimile
(206) 227-1320.
SUPPLEMENTARY INFORMATION:
Background
On October 15, 1991, Cessna Aircraft Company (Cessna), 6030 Cessna
Blvd., P.O. Box 7704, Wichita, KS 67277-7704, applied for a new type
certificate in the transport airplane category for the Model 750
(Citation X) airplane. The Cessna Model 750 is a T-tail, low swept
wing, medium-sized business jet powered by two GMA-3007C turbofan
engines mounted on pylons extending from the aft fuselage. Each engine
will be capable of delivering 6,000 pounds thrust. The flight controls
will be powered and capable of manual reversion. The airplane has a
seating capacity of up to twelve passengers, and a maximum takeoff
weight of 31,000 pounds. [[Page 28548]]
Type Certification Basis
Under the provisions of Sec. 21.17 of the FAR, Cessna must show,
except as provided in Sec. 25.2, that the Model 750 (Citation X) meets
the applicable provisions of part 25, effective February 1, 1965, as
amended by Amendments 25-1 through 25-74 and Amendment 25-80. In
addition, the proposed certification basis for the Model 750 includes
part 34, effective September 10, 1990, plus any amendments in effect at
the time of certification; and part 36, effective December 1, 1969, as
amended by Amendment 36-1 through the amendment in effect at the time
of certification. No exemptions are anticipated. This special condition
will form an additional part of the type certification basis.
If the Administrator finds that the applicable airworthiness
regulations (i.e., part 25, as amended) do not contain adequate or
appropriate safety standards for the Cessna Model 750 because of a
novel or unusual design feature, special conditions are prescribed
under the provisions of Sec. 21.16 to establish a level of safety
equivalent to that established in the regulations.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 of the FAR after public notice, as required by Secs. 11.28
and 11.29, and become part of the type certification basis in
accordance with Sec. 21.17(a)(2).
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same novel or
unusual design feature, the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
Novel or Unusual Design Features
The Model 750 incorporates new avionics/electronic installations,
including a digital Electronic Flight Instrument System (EFIS), Air
data System, Attitude and Heading Reference System (AHRS), Navigation
and Communication System, Autopilot System, and a Full Authority
Digital Engine Control (FADEC) system that controls critical engine
parameters. These systems may be vulnerable to high-intensity radiated
fields external to the airplane.
Discussion
At the time that Cessna applied for type certification of the
Cessna Model 750 (Citation X) airplane, the existing lightning
protection airworthiness certification requirements were insufficient
to provide an acceptable level of safety for new technology avionics
and electronic systems. The two existing regulations that specifically
pertained to lightning were Sec. 25.581 (the airframe in general), and
Sec. 25.954 (fuel system protection). There were, however, no
regulations that specifically addressed protection of electrical and
electronic systems from lightning.
On March 29, 1994, the FAA published in the Federal Register Notice
of Proposed Special Conditions No. SC-94-1-NM (59 FR 14571) for the
Cessna Model 750 (Citation X). These special conditions were proposed
requirements to protect the airplane systems from the effects of
lightning and high-intensity radiated fields (HIRF). Cessna, commenting
to the docket by letter, noted that there were differences in the
preamble language from the language used in issue papers that discussed
the proposed method of compliance with the special conditions. The FAA
agreed. Although the special conditions proposed were not changed from
the original notice, the methods of compliance discussed in the issue
papers that preceded the original notice were, in fact, different in
certain respects than the methods of compliance discussed in the
original notice. The FAA inadvertently left out Cessna's proposed
alternative methods of complying with the proposed special conditions.
As the methods of compliance proposed by Cessna deviate in certain
respects from previous methods of compliance with the proposed special
conditions, the FAA agreed these methods should also be made available
for the public record and comment as well. Therefore, Notice SC-94-1-NM
was republished in the Federal Register on September 12, 1994, as
Notice SC-94-1A-NM (59 FR 46775) in its entirety, including Cessna's
proposed alternative methods of compliance with the special conditions.
The FAA agrees with Cessna's proposed alternative method of testing
and evaluation of the effects of lightning on the installed airplane
systems when complying with the proposed special conditions. However,
lightning protection is no longer considered a novel or unusual design
feature relative to the regulations, as Amendment 25-80, effective May
21, 1994, was added to 14 CFR part 25 of the FAR (59 FR 22116, April
28, 1994). The lightning special condition differs from the rule in
that the definitions of critical and essential functions are retained
as a separate paragraph (i.e. item 3 in the notice). The rule also
provides approaches to compliance for designing and verifying lightning
protection in Sec. 25.1316(c) that would be no different than the
approaches to compliance for the special conditions.
As there is no longer a need for lightning special conditions, the
proposed lightning special condition has been removed from this final
special condition and Sec. 25.1316, as adopted by Amendment 25-80, will
be added to the Cessna 750 certification basis as authorized under
Sec. 21.17(a)(1)(i). Cessna's proposed method of testing and evaluation
of the effects of lightning on the installed airplane systems for
compliance with the lightning special condition can be utilized when
complying with Sec. 25.1316, as the intent of the lightning special
condition and Sec. 25.1316 are identical.
There is no specific regulation that addresses protection
requirements for electrical and electronic systems from HIRF. Increased
power levels from ground based radio transmitters and the growing use
of sensitive electrical and electronic systems to command and control
airplanes have made it necessary to provide adequate protection.
To ensure that a level of safety is achieved equivalent to that
intended by the regulations incorporated by reference, a special
condition is needed for the Cessna Model 750, to require that new
technology electrical and electronic systems, such as the EFIS, FADEC,
AHRS, etc., be designed and installed to preclude component damage and
interruption of function due to both the direct and indirect effects
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 electronic command and control of the airplane, the
immunity of critical digital avionics systems to HIRF must be
established.
It is not possible to precisely define the HIRF to which the
airplane will be exposed in service. There is also uncertainty
concerning the effectiveness of airframe shielding for HIRF.
Furthermore, coupling of electromagnetic energy to cockpit-installed
equipment through the cockpit window apertures is undefined. Based on
surveys and analysis of existing HIRF emitters, the FAA considers that
an adequate level of protection exists when compliance with the HIRF
protection special condition is shown with either paragraphs 1 or 2
below:
1. A minimum threat of 100 volts per meter peak electric field
strength from 10 KHz to 18 GHz.
a. The threat must be applied to the system elements and their
associated [[Page 28549]] wiring harnesses without the benefit of
airframe shielding.
b. Demonstration of this level of protection is established through
system tests and analysis.
2. A threat external to the airframe of the following field
strengths for the frequency ranges indicated.
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Peak (V/ Average
Frequency M) (V/M)
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10 KHz-100 KHz...................................... 50 50
100 KHz-500 KHz..................................... 60 60
500 KHz-2000 KHz.................................... 70 70
2 MHz-30 MHz........................................ 200 200
30 MHz-100 MHz...................................... 30 30
100 MHz-200 MHz..................................... 150 33
200 MHz-400 MHz..................................... 70 70
400 MHz-700 MHz..................................... 4,020 935
700 MHz-1000 MHz.................................... 1,700 170
1 GHz-2 GHz......................................... 5,000 990
2 GHz-4 GHz......................................... 6,680 840
4 GHz-6 GHz......................................... 6,850 310
6 GHz-8 GHz......................................... 3,600 670
8 GHz-12 GHz........................................ 3,500 1,270
12 GHz-18 GHz....................................... 3,500 360
18 GHz-40 GHz....................................... 2,100 750
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Cessna's market for the Model 750 Citation X includes, at the
present time, two European JAA member countries. Consequently, Cessna
intends to pursue certification to meet the European JAA requirements
as well as the FAA requirements. To reduce the testing required, Cessna
proposes to test to an environment that combines a proposed FAA
certification environment (from the SAE AE4R Subcommittee) and a
proposed JAA certification environment (from EUROCAE WG-33) to form a
``worst case'' certification environment. Cessna's proposed environment
consists of the following:
Where the combined proposed certification environment is less than
100 volts per meter, Cessna would test to the proposed certification
environment (JAA or FAA, whichever is higher). Where the combined
environment is greater than 100 volts per meter, Cessna would test to
the proposed JAA environment (less aircraft attenuation above 200 MHz).
The aircraft attenuation would be established by the results of full
vehicle tests conducted by Cessna on Model 650, Citation III, and
Citation VII aircraft. Cessna's proposed Model 750 HIRF certification
environment is as follows:
Proposed Cessna 750 (Citation X (CX)) HIRF Certification Environment
------------------------------------------------------------------------
Proposed FAA Proposed JAA
certification certification Proposed CX
Frequency (HZ) environment environment environment
(peak/avg) (peak/avg) (peak/avg)
------------------------------------------------------------------------
10K-500K.................... 50/50 40/40 50/50
500K-2M..................... 40/40 40/40 40/40
2M-30M...................... 100/100 100/100 100/100
30M-100M.................... 20/20 20/20 20/20
100M-200M................... 50/30 50/30 50/30
200M-400M................... 70/70 70/70 70/70
400M-700M................... 1520/750 700/30 700/30
700M-1G..................... 1300/170 1300/70 1300/70
1G-2G....................... 2500/180 2500/160 2500/160
2G-4G....................... 3500/360 3500/240 3500/240
4G-6G....................... 6800/280 3200/280 3200/280
6G-8G....................... 1800/330 800/330 800/330
8G-12G...................... 3500/215 3500/330 3500/330
12G-18G..................... 1700/270 1700/180 1700/180
------------------------------------------------------------------------
Discussion of Comments
There were no comments received in response to Notice SC-94-1-NM
other than those submitted by Cessna, as discussed earlier in this
document. No comments were received in response to Supplemental Notice
SC-94-1A-NM.
The Federal Aviation Administration's Analysis/Summary
The FAA does not agree with Cessna's proposed alternative method of
compliance (i.e., the proposed CX threat environment) for the
evaluation of the effects of HIRF on the installed airplane systems.
The FAA has not formally adopted any of the certification environments
proposed by Cessna listed above. The latest published FAA policy that
defines the external environment acceptable for airplane testing is
dated July 29, 1992, and is reflected earlier in the preamble to these
special conditions. If Cessna wishes to reduce testing by combining the
FAA and JAA environments, Cessna should test to the higher of the
values given in the environment tables that have been adopted by the
FAA and JAA. It should be noted that frequencies above 18 GHz should be
used only if the pass/fail criteria are not met in the 12-18 GHz range,
or if the system is designed to operate in the range from 18-40 GHz.
The FAA's option of testing using 100 volts per meter threat from
10 KHz to 18 GHz requires that this treat be applied to the systems
elements and associated wiring without the benefit of airframe
shielding. The 100 volts per meter test can be established by systems
tests and analysis acceptable to the FAA.
In summary, the FAA has determined that Cessna must utilize the
FAA's HIRF envelop (the first HIRF envelope and not the proposed SAE
AE4R envelop) or may combine the FAA HIRF envelope and the JAA envelope
and test to the greater values.
As discussed earlier in this document, the special conditions are
applicable initially to the Model 750. Should Cessna apply at a later
date for a change to the type certificate to include another model
incorporating that same novel or unusual design feature, the special
conditions would apply to that model as well, under the provisions of
Sec. 21.101(a)(1).
Conclusion
This action affects only certain design features on the Cessna
Model 750 (Citation X) airplane. It is not a rule of general
applicability and affects only the manufacturer who applied to the FAA
for approval of these features on the airplane.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and record keeping
requirements.
The authority citation for these special conditions is as follows:
Authority 49 U.S.C. app. 1344, 1348(c), 1352, 1354(a), 1355,
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et
seq.; E.O. 11514; and 49 U.S.C. 106(g).
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special condition is issued as part of the
type certification basis for the Cessna Model 750 (Citation X) series
airplanes.
1. Protection from Unwanted Effects of High-Intensity Radiated
Fields (HIRF). Each electrical and electronic system that performs
critical functions must be designed and installed to ensure that the
operation and operational capability of these systems to perform
critical functions are not adversely affected when the airplane is
exposed to high-intensity radiated fields.
2. For the purpose of this special condition, the following
definition applies: Critical Functions. Functions whose failure would
contribute to or cause a failure condition that would prevent the
continued safe flight and landing of the airplane.
[[Page 28550]] Issued in Renton, Washington, on May 8, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-13397 Filed 5-31-95; 8:45 am]
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