[Federal Register Volume 63, Number 123 (Friday, June 26, 1998)]
[Rules and Regulations]
[Pages 34784-34786]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-16960]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21 and 29

[Docket No. SW002; Special Condition No. 29-002-SC]


Special Conditions: Eurocopter France Model AS-365 N3 ``Dauphin'' 
Helicopters, Full Authority Digital Engine Control (FADEC)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special condition; request for comments.

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SUMMARY: This special condition is issued for the Eurocopter France 
Model AS-365 N3 ``Dauphin'' helicopters. These helicopters will have a 
novel or unusual design feature associated with the Full Authority 
Digital Engine Control (FADEC). The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards to 
protect systems that perform critical functions from the effects of 
high-intensity radiated fields (HIRF). This special condition contains 
the additional safety standards that the Administrator considers 
necessary to ensure that critical functions of systems will be 
maintained when exposed to HIRF.

DATES: The effective date of this special condition is June 17, 1998. 
Comments must be received on or before August 25, 1998.

ADDRESSES: Comments on this special condition may be mailed in 
duplicate to: Federal Aviation Administration, Office of the Regional 
Counsel, Southwest Region, Attention: Rules Docket No. SW002, Fort 
Worth, Texas 76193-0007 or deliver in duplicate to the Office of the 
Regional Counsel, Southwest Region, at 2601 Meacham Blvd., Fort Worth, 
Texas 76137. Comments must be marked: Rules Docket No. SW002. Comments 
may be inspected in the Rules Docket weekdays, except Federal holidays, 
between 8:30 a.m. and 4:00 p.m.

FOR FURTHER INFORMATION CONTACT: Carroll Wright, FAA, Rotorcraft 
Directorate, Regulations Group, Fort Worth, Texas 76193-0111; telephone 
817-222-5120, fax 817-222-5961.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice and 
opportunity for prior public comment hereon are impracticable because 
these procedures would significantly delay issuance of the approval 
design and thus delivery of the affected aircraft. In addition, notice 
and opportunity for prior public comment are unnecessary since the 
substance of this special condition has been subject to the public 
comment process in several prior instances with no substantive comments 
received. The FAA therefore finds that good cause exists for making 
this special condition effective upon issuance.

Comments Invited

    Interested persons are invited to submit such written data, views, 
or arguments as they may desire. Communications should identify the 
regulatory docket and be submitted in duplicate to the address 
specified above. All communications received on or before the closing 
date for comments will be considered by the Administrator. The special 
condition may be changed in light of the comments received. All 
comments received will be available in the Rules Docket for examination 
by interested persons, both before and after the closing date for 
comments. A report summarizing each substantive public contact with FAA 
personnel concerning this rulemaking will be filed in the docket. 
Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this Special Condition must include a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Rules Docket No. SW002'' The postcard will be date 
stamped and returned to the commenter.

Background

    On September 1, 1997, Eurocopter France applied for an amendment to 
Type Certificate (TC) No. H10EU to include the new Model AS-365 N3 
``Dauphin'' helicopter. The Model AS-365 N3 ``Dauphin'' helicopter, 
which is a derivative of the Model AS-365 N2 helicopter that is 
currently approved under TC No. H10EU, is a transport category A and B 
helicopter powered by two Turbomeca Arriel 2C engines with FADEC. The 
Turbomeca Arriel 1C2 engine has been replaced with the Turbomeca Arriel 
2C engine, which includes a digital engine control system.

Type Certification Basis

    Under the provisions of 14 CFR Sec. 21.101, Eurocopter France must 
show that the Model AS-365 N3 ``Dauphin'' helicopter meets the 
applicable provisions of the regulations incorporated by reference in 
TC No. H10EU or the applicable regulations in effect on the date of 
application for the change to the Model No. AS-365 N3. The regulations 
incorporated by reference in the type certificate are commonly referred 
to as the ``original type certification basis.'' The regulations 
incorporated by reference in H10EU are as follows: Sec. 21.29 and 14 
CFR part 29, effective February 1, 1965, plus Amendments 29-1 through 
29-11. In addition, the applicant elected to comply with 14 CFR part 29 
amendments 29-12 through 29-16, except for 14 CFR part 29.397 
concerning the rotorbrake. The certification basis also includes 
certain special conditions and equivalent safety findings that are not 
relevant to this special condition.
    If the Administrator finds that the applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
these helicopters because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model AS-365 N3 helicopter must comply with the noise 
certification requirements of 14 CFR part 36; and the FAA must issue a 
finding of regulatory adequacy pursuant to Sec. 611 of Public Law 92-
574, the ``Noise Control Act of 1972.''
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49, as required by Secs. 11.28 and 11.29(b), and become part of 
the type certification basis in accordance with Sec. 21.101(b)(2).

[[Page 34785]]

    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, or should any other model already included on 
the same type certificate be modified to incorporate 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 Eurocopter France Model AS-365 N3 ``Dauphin'' helicopter will 
incorporate the following novel or unusual design features: Electrical, 
electronic, or combination of electrical electronic (electrical/
electronic) systems, such as FADEC, that will be performing functions 
critical to the continued safe flight and landing of the helicopter. 
FADEC is an electronic device that performs the functions of engine 
control.

Discussion

    The Eurocopter France Model AS-365 N3 ``Dauphin'' helicopter, at 
the time of application, was identified as having modifications that 
incorporate one and possibly more electrical/electronic systems, such 
as FADEC. After the design is finalized, Eurocopter France will provide 
the FAA with a preliminary hazard analysis that will identify any other 
critical functions required for safe flight and landing that are 
performed by the electrical/electronic systems.
    Recent advances in technology have given rise to the application in 
aircraft designs of advanced electrical/electronic systems that perform 
critical functions. These advanced systems respond to the transient 
effects of induced electrical current and voltage caused by HIRF 
incident on the external surface of the helicopter. These induced 
transient currents and voltages can degrade the performance of the 
electrical/ electronic systems by damaging the components or by 
upsetting the systems' functions.
    Furthermore, the electromagnetic environment has undergone a 
transformation not envisioned by the current application of 14 CFR 
Sec. 29.1309(a). Higher energy levels radiate from operational 
transmitters currently used for radar, radio, and television. Also, the 
number of HIRF transmitters has increased significantly.
    Existing aircraft certification requirements are inappropriate in 
view of these technological advances. In addition, the FAA has received 
reports of some significant safety incidents and accidents involving 
military aircraft equipped with advanced electrical/electronic systems 
when they were exposed to electromagnetic radiation.
    The combined effects of the technological advances in helicopter 
design and the changing environment have resulted in an increased level 
of vulnerability of the electrical/electronic systems required for the 
continued safe flight and landing of the helicopter. Effective measures 
to protect these helicopters against the adverse effects of exposure to 
HIRF will be provided by the design and installation of these systems. 
The following primary factors contributed to the current conditions: 
(1) increased use of sensitive electronics that perform critical 
functions; (2) reduced electromagnetic shielding afforded helicopter 
systems by advanced technology airframe materials; (3) adverse service 
experience of military aircraft using these technologies; and (4) an 
increase in the number and power of radio frequency transmitters and 
the expected increase in the future.
    The FAA recognizes the need for aircraft certification standards to 
keep pace with the developments in technology and environment and, in 
1986, initiated a high-priority program to (1) determine and define 
electromagnetic energy levels; (2) develop and describe guidance 
material for design, test, and analysis; and (3) prescribe and 
promulgate regulatory standards.
    The FAA participated with industry and airworthiness authorities of 
other countries to develop internationally recognized standards for 
certification.
    The FAA and airworthiness authorities of other countries have 
identified two levels of the HIRF environment to which a helicopter 
could be exposed, one environment for VFR operations and a different 
environment for IFR operations. While the HIRF rulemaking requirements 
are being finalized, the FAA is adopting a special condition for the 
certification of aircraft that employ electrical/electronic systems 
that perform critical functions. The accepted maximum energy levels 
that civilian helicopter system installations must withstand for safe 
operation are based on surveys and analysis of existing radio frequency 
transmitters. This special condition will require the helicopters' 
electrical/electronic systems and associated wiring to be protected 
from these energy levels. These external threat levels are believed to 
represent the worst-case exposure for a helicopter operating under VFR 
or IFR.
    Compliance with HIRF requirements will be demonstrated by tests, 
analysis, computer models, similarity with existing systems, or a 
combination of these methods. Service experience alone will not be 
acceptable since such experience in normal flight operations may not 
include an exposure to HIRF. Reliance on a system with similar design 
features for redundancy, as a means of protection against the effects 
of external HIRF, is generally insufficient because all elements of a 
redundant system are likely to be concurrently exposed to the radiated 
fields.
    This special condition will require the systems that perform 
critical control functions, or provide critical displays as installed 
in the aircraft, to meet certain standards based on either a defined 
HIRF environment or a fixed value using laboratory tests. Control 
system failures and malfunctions can more directly and abruptly 
contribute to a catastrophic event than display system failures and 
malfunctions. Therefore, it is considered appropriate to require more 
rigorous HIRF verification methods for critical control systems than 
for critical display systems.
    The applicant may demonstrate that the operation and operational 
capabilities of the installed electrical/electronic systems that 
perform critical functions are not adversely affected when the aircraft 
is exposed to the defined HIRF test environment. The FAA has determined 
that the test environment defined in Table 1 is acceptable for critical 
control functions in helicopters. The test environment defined in Table 
2 is acceptable for critical display systems in helicopters.
    The applicant may also demonstrate by a laboratory test that the 
electrical/electronic systems that perform critical control, or provide 
critical displays, can withstand a peak electromagnetic field strength 
in a frequency range of 10 KHz to 18 GHz. If a 
laboratory test is used to show compliance with the defined HIRF 
environment, no credit will be given for signal attenuation due to 
installation. A level of 100 volts per meter (v/m) is appropriate for 
critical displays systems. A level of 200 v/m is appropriate for 
critical control functions. Laboratory test levels are defined 
according to RTCA/DO-160D Section 20 Category W (100 v/m and 150 mA) 
and Category Y (200 v/m and 300 mA). As defined in DO-160D Section 20, 
the test levels are defined as the peak of the root mean square (rms) 
envelope. As a minimum, the modulations required for RTCA/DO-160D 
Section 20 Categories W and Y will be used. Other modulations should be 
selected for the signal most

[[Page 34786]]

likely to disrupt the operation of the system under test, based on its 
design characteristics. For example, flight control systems may be 
susceptible to 3 Hz square wave modulation while the video 
signals for electronic display systems may be susceptible to 400 
Hz sinusoidal modulation. If the worst-case modulation is 
unknown or cannot be determined, default modulations may be used. 
Suggested default values are a 1 KHz sine wave with 80 
percent depth of modulation in the frequency range from 10 
KHz to 400 MHz and 1 KHz square wave 
with greater than 90 percent depth of modulation from 400 
MHz to 18 GHz. For frequencies where the 
unmodulated signal would cause deviations from normal operation, 
several different modulating signals with various waveforms and 
frequencies should be applied.
    Applicants must perform a preliminary hazard analysis to identify 
electrical/electronic systems that perform critical functions. The term 
``critical'' means those functions whose failure would contribute to or 
cause an unsafe condition that would prevent the continued safe flight 
and landing of the helicopter. The systems identified by the hazard 
analysis as performing critical functions are required to have HIRF 
protection. A system may perform both critical and noncritical 
functions. Primary electronic flight display systems and their 
associated components perform critical functions such as attitude, 
altitude, and airspeed indications. HIRF requirements would apply only 
to the systems that perform critical functions.
    Acceptable system performance would be attained by demonstrating 
that the critical function components of the system under consideration 
continue to perform their intended function during and after exposure 
to required electromagnetic fields. Deviations from system 
specifications may be acceptable but must be independently assessed by 
the FAA on a case-by-case basis.

           Table 1.--VFR Rotorcraft Field Strength Volts/Meter          
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                     Frequency                         Peak     Average 
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10-100 KHz........................................        150        150
100-500...........................................        200        200
500-2000..........................................        200        200
2-30 MHz..........................................        200        200
30-100............................................        200        200
100-200...........................................        200        200
200-400...........................................        200        200
400-700...........................................        730        200
700-1000..........................................       1400        240
1-2 GHz...........................................       5000        250
2-4...............................................       6000        490
4-6...............................................       7200        400
6-8...............................................       1100        170
8-12..............................................       5000        330
12-18.............................................       2000        330
18-40.............................................       1000        420
------------------------------------------------------------------------


           Table 2.--IFR Rotorcraft Field Strength Volts/Meter          
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                     Frequency                         Peak     Average 
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10-100 KHz........................................         50         50
100-500...........................................         50         50
500-2000..........................................         50         50
2-30 MHz..........................................        100        100
30-70.............................................         50         50
70-100............................................         50         50
100-200...........................................        100        100
200-400...........................................        100        100
400-700...........................................        700         50
700-1000..........................................        700        100
1-2 GHz...........................................       2000        200
2-4...............................................       3000        200
4-6...............................................       3000        200
6-8...............................................       1000        200
8-12..............................................       3000        300
12-18.............................................       2000        200
18-40.............................................        600        200
------------------------------------------------------------------------

Applicability

    As previously discussed, this special condition is applicable to 
Model AS-365 N3 helicopters. Should Eurocopter France apply at a later 
date for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, the special 
condition would apply to that model as well under the provisions of 
Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of helicopters. It is not a rule of general 
applicability and affects only the applicant who applied to the FAA for 
approval of these features on the helicopters.
    The substance of this special condition has been subjected to the 
notice and comment procedures in several prior instances and has been 
derived without substantive change from those previously issued. It is 
unlikely that prior public comment would result in a significant change 
from the substance contained herein. For this reason and because a 
delay would significantly affect the certification of the helicopter, 
which is imminent, the FAA has determined that prior public notice and 
comment are unnecessary and impracticable, and good cause exists for 
adopting this special condition upon issuance. The FAA is requesting 
comments to allow interested persons to submit views that may not have 
been submitted in response to the prior opportunities for comment 
described above.

List of Subjects in 14 CFR Part 21 and 29

    Aircraft, Air transportation, Aviation safety, Rotorcraft, Safety.

    The authority citation for these special conditions is as follows: 
42 USC 7572; 49 USC. 106(g), 40105, 40113, 44701-44702, 44704, 44709, 
44711, 44713, 44715, 45303.

The Special Condition

    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 Eurocopter France Model AS 365 N3 
``Dauphin'' helicopters.

Protection for Electrical and Electronic Systems From High Intensity 
Radiated Fields

    Each system that performs critical functions must be designed and 
installed to ensure that the operation and operational capabilities of 
these critical functions are not adversely affected when the helicopter 
is exposed to high intensity radiated fields external to the 
helicopter.

    Issued in Fort Worth, Texas, on June 17, 1998.
Eric Bries,
Acting Manager, Rotorcraft Directorate Aircraft Certification Service, 
ASW-100.
[FR Doc. 98-16960 Filed 6-25-98; 8:45 am]
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