[Federal Register Volume 63, Number 123 (Friday, June 26, 1998)]
[Rules and Regulations]
[Pages 34786-34789]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-16959]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 27

[Docket No. SW001; Special Conditions No. 27-001-SC]


Special Conditions: Eurocopter Model AS-350 B3 ``Ecureuil'' 
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 Model AS-
350 B3 ``Ecureuil'' helicopters. These helicopters will have a novel or 
unusual design feature associated with the Full Authority Digital 
Engine Control

[[Page 34787]]

(FADEC). The applicable airworthiness regulations do not contain 
adequate or appropriate safety standards to protect systems that 
perform critical control functions, or provide critical displays, 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 April 30, 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, Attention: Rules Docket No. SW001, Fort Worth, Texas 76193-
0007 or deliver in duplicate to the Office of the Regional Counsel at 
2601 Meacham Blvd., Fort Worth, Texas 76137. Comments must be marked: 
Rules Docket No. SW001. 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 design 
approval and thus delivery of the affected aircraft. In addition, 
notice and opportunity for prior public comment are unnecessary since 
the substance of these special conditions 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 or special condition number 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. SW001.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On June 18, 1997, Eurocopter applied for an amendment to Type 
Certificate (TC) No. H9EU to include the new Model AS-350 B3 
``Ecureuil'' helicopter. The Model AS-350 B3 ``Ecureuil'' helicopter, 
which is a derivative of the AS-350 B/B1/B2 versions currently approved 
under TC No. H9EU, is a normal category five-passenger helicopter 
powered by a Turbomeca Arriel 2B engine with FADEC. The Model AS-350 B3 
is derived from the Model AS-350 B2 with the following main 
modifications: (1) Turbomeca Arriel 2B engine with digital engine 
control system; (2) Powerplant instruments on Liquid Crystal Display; 
and (3) AS-355 N type tail rotor.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Eurocopter must show that 
the Model AS-350 B3 ``Ecureuil'' helicopter meets the applicable 
provisions of the regulations incorporated by reference in TC No. H9EU 
or the applicable regulations in effect on the date of application for 
the change to the Model AS-350 B3. 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 H9EU are as follows: Sec. 21.29 and 14 CFR part 27, 
effective February 1, 1965, plus Amendments 27-1 through 27-10. In 
addition, the certification basis 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-350 B3 must comply with the noise 
certification requirements of 14 CFR part 36; and the FAA must issue a 
finding of regulatory adequacy pursuant to section 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).
    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 Model AS-350 B3 ``Ecureuil'' helicopters 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 Model AS-350 B3 ``Ecureuil'' 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 will provide the FAA with a 
preliminary hazard analysis that will identify any other critical 
functions, required for safe flight and landing, 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 
Sec. 27.1309(a).

[[Page 34788]]

Higher energy levels radiate from operational transmitters currently 
used for radar, radio, and television. Also, the number of 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 emitters 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 that a helicopter could 
be exposed to, 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 control functions, or provide critical displays. 
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 emitters. 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, 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 display 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 means squared (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 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 helicopters. 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, including control and 
display.
    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

[[Page 34789]]

                                                                        
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
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           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 
the Model AS-350 B3 helicopter. Should Eurocopter 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 helicopter. 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 helicopter.
    The substance of this special condition has been subjected to the 
notice and comment procedure 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 Parts 21 and 27

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

    The authority citation for this special condition is as follows: 42 
U.S.C. 7572; 49 U.S.C. 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 Model AS-350 B3 ``Ecureuil'' 
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 April 30, 1998.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 98-16959 Filed 6-25-98; 8:45 am]
BILLING CODE 4910-13-P