[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
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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
