[Federal Register Volume 61, Number 115 (Thursday, June 13, 1996)]
[Rules and Regulations]
[Pages 29928-29931]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-14761]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 27
[Docket No. 96-ASW-1; Special Condition No. 27-ASW-3]
Special Condition: Agusta Models A109D and A109E, High Intensity
Radiated Fields
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special condition; request for comments.
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SUMMARY: This special condition is issued for the Agusta Model A109D
and A109E helicopters. These helicopters will have a novel or unusual
design feature associated with electronic systems that perform critical
functions. The applicable airworthiness regulations do not contain
adequate or appropriate safety standards for the protection of the
electronic systems that perform critical functions from the effects of
external high intensity radiated fields (HIRF). 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 applicable airworthiness standards.
DATES: The effective date of this special condition is June 13, 1996.
Comments must be received on or before August 12, 1996.
ADDRESSES: Comments on this proposal may be mailed in duplicate to the
Federal Aviation Administration (FAA), Office of the Assistant Chief
Counsel, Attn: Rules Docket No. 96-ASW-1, Fort Worth, Texas 76193-0007,
or delivered in duplicate to the Office of the Assistant Chief Counsel,
2601 Meacham Blvd., Fort Worth, Texas. Comments must be marked Docket
No. 96-ASW-1. Comments may be inspected in the Rules Docket weekdays,
except Federal holidays, between 9 a.m. and 3 p.m.
FOR FURTHER INFORMATION CONTACT:
Mr. Carroll Wright, FAA, Rotorcraft Directorate, Regulations Group,
Fort Worth, Texas 76193-0111; telephone (817) 222-5120.
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 delay delivery of the affected helicopter. These
notice and comment procedures are also considered unnecessary since the
public has been previously provided with a substantial number of
opportunities to comment on substantially identical special conditions,
and their comments have been fully considered. Therefore, good cause
exists for making this special condition effective upon issuance.
Comments Invited
Although this final special condition was not subject to notice and
opportunity for prior public comment, comments are invited on this
final special condition. Interested persons are invited to comment on
this final special condition by submitting such written data, views, or
arguments as they may desire. Communications should identify the
regulatory docket number and be submitted in duplicate to the address
specified under the caption ADDRESSES. All communications received on
or before the closing date for comments will be considered. This
special condition may be changed in light of comments received. All
comments received will be available in the Rules Docket for examination
by interested persons, both before and after the closing date of
comments. A report summarizing each substantive public contact with FAA
personnel concerning this rulemaking will be filed in the docket.
Persons wishing the FAA to acknowledge receipt of their comments
submitted in response to this final rule must submit with those
comments a self-addressed, stamped postcard on which the following
statement is made: ``Comments to Docket No. 96-ASW-3.'' The postcard
will be date and time stamped and returned to the commenter.
Background
Agusta S.p.A., Cascina Costa, Italy, applied for an amendment to
U.S. Type Certificate H7EU through the Registro Aeronautico Italiano
(RAI) September 23, 1992, updated July 26, 1993, to include Model A109D
and A109E helicopters based on previously certified A109C and A109K2
helicopters. The A109D and A109E helicopters differ from the previously
certificated model helicopters because they contain the following:
a. Allison 250-C22(A109D) or Pratt & Whitney PW206C(A109E) FADEC
controlled engines.
b. A main landing gear that is held in position by two crossbeams
that are covered by pods and is retractable into the bottom of the
helicopter.
c. A new main rotor titanium hub, composite tension links,
electomeric bearings, with dampers derived from the Model A129
helicopter.
d. Updated fuselage and fuel systems; and
e. A new cockpit layout with flat panel displays (IDS) for
powerplant data monitoring.
Type Certification Basis
The certification basis established for the Agusta Model A109D and
A109E helicopters includes: 14 Code of Federal Regulations (CFR)
Sec. 21.29 and 14 CFR part 27 effective February 1, 1965, including
Amendments 27-1 through 27-8, except as more specifically required by
the following paragraph amendment levels:
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Paragraph Amendment
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27.2......................................................... 28
27.21........................................................ 21
27.45........................................................ 21
27.71........................................................ 21
27.79........................................................ 21
27.141....................................................... 21
27.143....................................................... 21
27.175....................................................... 21
27.177....................................................... 21
27.401....................................................... 27
27.610....................................................... 21
27.901....................................................... 23
27.903....................................................... 23
27.927....................................................... 23
27.954....................................................... 23
27.1091...................................................... 23
27.1093(b)................................................... 23
27.1189...................................................... 23
27.1305...................................................... 23
27.1309...................................................... 21
27.1321...................................................... 13
[[Page 29929]]
27.1322...................................................... 11
27.1323...................................................... 13
27.1325...................................................... 13
27.1401...................................................... 10
27.1505...................................................... 21
27.1519...................................................... 21
27.1521...................................................... 23
27.1527...................................................... 14
27.1529...................................................... 18
27.1549...................................................... 23
27.1555...................................................... 21
27.1557...................................................... 11
27.1581...................................................... 14
27.1583...................................................... 16
27.1585...................................................... 21
27.1587...................................................... 21
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Section 29.903(b), effective February 1, 1965, for category ``A''
engine isolation, elected by the applicant; Special Conditions No. 27-
54-EU-17 for Agusta Model A109 helicopter, issued on June 26, 1973;
equivalent safety in lieu of compliance shown for:
Section 27.1189, regarding shut-off means, and
Section 27.1305(d), regarding the fuel quantity indicator.
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 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 after public notice, 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).
Discussion
The Agusta Model A109D and A109E helicopters, at the time of the
application for amendment to U.S. Type Certificate H7EU, were
identified as incorporating one and possibly more electrical,
electronic, or combination of electrical and electronic (electrical/
electronic) systems that will perform functions critical to the
continued safe flight and landing of the helicopters. A FADEC is an
electronic device that performs the critical functions of engine
control. The control of the engines is critical to the continued safe
flight and landing of the helicopter during visual flight rules (VFR)
and instrument flight rules (IFR) operations.
If it is determined that this helicopter currently or at a future
date incorporates other electrical/electronic systems performing
critical functions, those systems also will be required to comply with
the requirements of this special condition.
Recent advances in technology have prompted the design of aircraft
that include advanced electrical and electronic systems that perform
functions required for continued safe flight and landing. However,
these advanced systems respond to the transient effects of induced
electrical current and voltage caused by the HIRF incident on the
external surface of the helicopters. 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. 29.1309(a). Higher energy levels radiate from operational
transmitters currently used for radar, radio, and television; 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 technological advances in helicopter design
and the changing environment have resulted in an increased level of
vulnerability of the electrical and electronic systems required for the
continued safe flight and landing of the helicopters. 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 technological developments and a changing environment
and, in 1986, initiated a high priority program to (1) determine and
define electromagnetic energy levels; (2) develop 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 a level of HIRF environment that a helicopter could be
exposed to during IFR operations. While the HIRF 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
emitters. This special condition will require the helicopters'
electrical/electronic systems and associated wiring be protected from
these energy levels. These external threat levels are believed to
represent the worst-case exposure for a helicopter operating under IFR.
The HIRF environment specified in this special condition is based
on many critical assumptions. With the exception of takeoff and landing
at an airport, one of these assumptions is the aircraft would be not
less than 500 feet above ground level (AGL). Helicopters operating
under visual flight rules (VFR) routinely operate at less than 500 feet
AGL and perform takeoffs and landings at locations other than
controlled airports. Therefore, it would be expected that the HIRF
environment experienced by a helicopter operating VFR may exceed the
defined environment by 100 percent or more.
This special condition will require the systems that perform
critical functions, as installed in the aircraft, to meet certain
standards based on either a defined HIRF environment or a fixed value
using laboratory tests.
The applicant may demonstrate that the operation and operational
capability of the installed electrical/electronic systems that perform
critical functions are not adversely affected when the aircraft is
exposed to the defined HIRF environment. The FAA has determined that
the environment defined in Table 1 is acceptable for critical functions
in
[[Page 29930]]
helicopters operating at or above 500 feet AGL. For critical functions
of helicopters operating at less than 500 feet AGL, additional factors
must be considered.
The applicant may also demonstrate by a laboratory test that the
electrical/electronic systems that perform critical functions 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 v/m and other
considerations, such as an alternate technology backup that is immune
to HIRF, are appropriate for critical functions during IFR operations.
A level of 200 v/m and further considerations, such as an alternate
technology backup that is immune to HIRF, are more appropriate for
critical functions during VFR operations.
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 a failure 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.
Compliance with HIRF requirements will be demonstrated by tests,
analysis, models, similarity with existing systems, or a combination of
these methods. The two basic options of either testing the rotorcraft
to the defined environment or laboratory testing may not be combined.
The laboratory test allows some frequency areas to be under tested and
requires other areas to have some safety margin when compared to the
defined environment. The areas required to have some safety margin are
those that have been, by past testing, shown to exhibit greater
susceptibility to adverse effects from HIRF; and laboratory tests, in
general, do not accurately represent the aircraft installation. 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.
The modulation that represents the signal most likely to disrupt
the operation of the system under test, based on its design
characteristics, should be selected. For example, flight control system
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.
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.--Field Strength Volts/Meter
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Frequency Peak Average
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10-100 KHz............................................ 50 50
100-500............................................... 60 60
500-2000.............................................. 70 70
2-30 MHz.............................................. 200 200
30-100................................................ 30 30
100-200............................................... 150 33
200-400............................................... 70 70
400-700............................................... 4020 935
700-1000.............................................. 1700 170
1-2 GHz............................................... 5000 990
2-4................................................... 6680 840
4-6................................................... 6850 310
6-8................................................... 3600 670
8-12.................................................. 3500 1270
12-18................................................. 3500 360
18-40................................................. 2100 750
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As discussed above, these special conditions are applicable
initially to the Model A109D and A109E helicopters. Should Agusta 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 conditions would apply to that model as well, under the
provisions of Sec. 21.101(a)(1).
Conclusion
This action affects only certain unusual or novel design features
on two models of 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 affected helicopter.
The substance of this special condition for similar installations
in a variety of helicopters has been subjected to the notice and
comment procedure and has been finalized without substantive change. 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 impractical, and good cause
exists for adopting this special condition immediately. Therefore, this
special condition is being made effective upon issuance. The FAA is
requesting comments to allow interested persons to submit views that
may not have been submitted in response to prior opportunities for
comment.
List of Subjects in 14 CFR Parts 21 and 29
Aircraft, Air transportation, Aviation safety, Rotorcraft, Safety.
The authority citation for this special condition is as follows:
Authority: 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 Federal Aviation Administration (FAA) issues the
following special condition as a part of the type certification basis
for the Agusta Model A109D and A109E 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
helicopters are exposed to high intensity radiated fields external to
the helicopters.
[[Page 29931]]
Issued in Fort Worth, Texas, on May 31, 1996.
Daniel P. Salvano,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 96-14761 Filed 6-12-96; 8:45 am]
BILLING CODE 4910-13-M
