[Federal Register Volume 60, Number 124 (Wednesday, June 28, 1995)]
[Rules and Regulations]
[Pages 33332-33333]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-15889]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. 125CE, Special Condition 23-ACE-81]
Special Conditions; Twin Commander Model 695 Airplane
AGENCY Federal Aviation Administration (FAA), DOT.
ACTION; Final special conditions; request for comments.
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SUMMARY: These special conditions are issued for the Twin Commander
Model 695 airplane modified by Garrett Aviation Services, Augusta,
Georgia. This airplane will have novel and unusual design features when
compared to the state of technology envisaged in the applicable
airworthiness standards. These novel and unusual design features
include the installation of electronic displays for which the
applicable regulations do not contain adequate or appropriate
airworthiness standards for the protection of these systems from the
effects of high intensity radiated fields (HIRF). These special
conditions contain the additional safety standards that the
Administrator considers necessary to establish a level of safety
equivalent to the airworthiness standards applicable to these
airplanes.
EFFECTIVE DATE: The effective date of these special conditions is June
28, 1995. Comments must be received on or before July 28, 1995.
ADDRESSES: Comments may be mailed in duplicate to: Federal Aviation
Administration, Office of the Assistant Chief Counsel, ACE-7,
Attention: Rules Docket Clerk, Docket No. 125CE, Room 1558, 601 East
12th Street, Kansas City, Missouri 64106. All comments must be marked:
Docket No. 125CE. Comments may be inspected in the Rules Docket
weekdays, except Federal holidays, between 7:30 a.m. and 4:00 p.m.
FOR FURTHER INFORMATION CONTACT: Ervin Dvorak, Aerospace Engineer,
Standards Office (ACE-110), Small Airplane Directorate, Aircraft
Certification Service, Federal Aviation Administration, 601 East 12th
Street, Kansas City, Missouri 64106; telephone (816) 426-6941.
SUPPLEMENTARY INFORMATION:
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety, and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
these special conditions.
Interested persons are invited to submit such written data, views,
or arguments as they may desire. Communications should identify the
regulatory docket and special conditions 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. These special conditions may be changed in light of the
comments received. All comments submitted will be available in the
rules docket for examination by interested parties, 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. Persons wishing the FAA to
acknowledge receipt of their comments, submitted in response to this
request, must include a self-addressed and stamped postcard on which
the following statement is made: ``Comments to Docket No. 125CE.'' The
postcard will be date stamped and returned to the commenter.
Background
On October 31, 1994, Garrett Aviation Services, 1550 Hangar Road,
Augusta, Georgia 30906, made an application to the FAA for a
supplemental type certificate (STC) for the Twin Commander Model 695
airplane. The proposed modification incorporates a novel or unusual
design feature, such as digital avionics consisting of an electronic
flight instrument system (EFIS), that is vulnerable to HIRF external to
the airplane.
Type Certification Basis
The type certification basis for the Twin Commander Model 695
Airplane is given in Type Certification Data Sheet No. 2A4 plus the
following:
Sec. 23.1301 of Amendment 23-20; Secs. 23.1309, 23.1311, and
23.1321 of Amendment 23-41 and Sec. 23.1322 of Amendment 23-43;
exemptions, if any; and the special conditions adopted by this remaking
action.
Discussion
The FAA may issue and amend special conditions, as necessary, as
part of the type certification basis if the Administrator finds that
the airworthiness standards, designated according to Sec. 21.101(b), do
not contain adequate or appropriate safety standards because of novel
or unusual design features of an airplane. 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 are normally issued according to Sec. 11.49, after public
notice, as required by Secs. 11.28 and 11.29(b), effective October 14,
1980, and become a part of the type certification basis in accordance
with Sec. 21.101(b)(2).
Garrett Aviation Services, plans to incorporate certain novel and
unusual design features into an airplane for which the airworthiness
standards do not contain adequate or appropriate safety standards for
protection from the effects of HIRF. These features include electronic
systems, which are susceptible to the HIRF environment, that were not
envisaged by the existing regulations for this type of airplane.
Protection of Systems From High Intensity Radiated Fields (HIRF):
Recent advances in technology have given rise to the application in
aircraft designs of advanced electrical and electronic systems that
perform functions required for continued safe flight and landing. Due
to the use of sensitive solid state advanced components in analog and
digital electronics circuits, these advanced systems are readily
responsive to the transient effects of induced electrical current and
voltage caused by the HIRF. The HIRF can degrade electronic systems
performance by damaging components or upsetting system functions.
Furthermore, the HIRF environment has undergone a transformation
that was not foreseen when the current requirements were developed.
Higher energy levels are radiated from transmitters that are used for
radar, radio, and television. Also, the number of transmitters has
increased significantly. There is also uncertainty concerning the
effectiveness of airframe shielding for HIRF. Furthermore, coupling to
cockpit-installed equipment through the cockpit window apertures is
undefined.
The combined effect of the technological advances in airplane
design and the changing environment has resulted in an increased level
of vulnerability of electrical and electronic systems required for the
continued safe [[Page 33333]] flight and landing of the airplane.
Effective measures against the effects of exposure to HIRF must be
provided by the design and installation of these systems. The accepted
maximum energy levels in which civilian airplane system installations
must be capable of operating safely are based on surveys and analysis
of existing radio frequency emitters. These special conditions require
that the airplane be evaluated under these energy levels for the
protection of the electronic system and its associated wiring harness.
These external threat levels, which are lower than previous required
values, are believed to represent the worst case to which an airplane
would be exposed in the operating environment.
These special conditions require qualification of systems that
perform critical functions, as installed in aircraft, to the defined
HIRF environment in paragraph 1 or, as an option to a fixed value using
laboratory tests, in paragraph 2, as follows:
(1) The applicant may demonstrate that the operation and
operational capability of the installed electrical and electronic
systems that perform critical functions are not adversely affected when
the aircraft is exposed to the HIRF environment defined below:
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
30-70............................................... 30 30
70-100.............................................. 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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or,
(2) The applicant may demonstrate by a system test and analysis
that the electrical and electronic systems that perform critical
functions can withstand a minimum threat of 100 volts per meter,
peak electrical field strength, from 10 KHz to 18 GHz. When using
this test to show compliance with the HIRF requirements, no credit
is given for signal attenuation due to installation.
A preliminary hazard analysis must be performed by the applicant,
for approval by the FAA, to identify electrical and/or 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 airplane. The systems identified by the hazard analysis that
perform critical functions are candidates for the application of HIRF
requirements. A system may perform both critical and non-critical
functions. Primary electronic flight display systems, and their
associated components, perform critical functions such as attitude,
altitude, and airspeed indication. The HIRF requirements apply only to
critical functions.
Compliance with HIRF requirements may be demonstrated by tests,
analysis, models, similarly with existing systems, or any combination
of these. Service experience alone is not acceptable since normal
flight operations may not include an exposure to the HIRF environment.
Reliance on a system with similar design features for redundancy as a
means of protection against the effects of external HIRF is generally
insufficient since all elements of a redundant system are likely to be
exposed to the fields concurrently.
Conclusion
In view of the design features discussed for the Twin Commander
Model 695 Airplane, the following special conditions are issued. This
action is not a rule of general applicability and affects only those
applicants who apply to the FAA for approval of these features on these
airplanes.
The substance of these special conditions has been subject to the
notice and public comment procedure in several prior rulemaking
actions. For example, the Dornier 228-200 (53 FR 14782, April 26,
1988), the Cessna Model 525 (56 FR 49396, September 30, 1991), and the
Beech Model 200, A200, and B200 airplanes (57 FR 1220, January 13,
1992). It is unlikely that additional public comment would result in
any significant change from those special conditions already issued and
commented on. For these reasons, and because a delay would
significantly affect the applicant's installation of the system and
certification of the airplane, which is imminent, the FAA has
determined that prior public notice and comment are unnecessary and
impracticable, and good cause exists for adopting these special
conditions without notice. Therefore, these special conditions are
being made effective upon publication in the Federal Register. However,
as previously indicated, interested persons are invited to comment on
these special conditions if they so desire.
List of Subjects in 14 CFR Part 23
Aircraft, Aviation safety, Signs and symbols
Citation
The authority citation for these special conditions is as follows:
Authority: Secs. 313(a), 601, and 603 of the Federal Aviation
Act of 1958; as amended (49 U.S.C. 1354(a), 1421, and 1423); 49
U.S.C. 106(g); 14 CFR 21.16 and 21.101; and 14 CFR 11.28 and 11.49.
Adoption of Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the modified Twin Commander Model 695
airplane:
1. Protection of Electrical and Electronic Systems from High
Intensity Radiated Fields (HIRF). Each system that performs critical
functions must be designed and installed to ensure that the operations,
and operational capabilities of these systems to perform critical
functions, are not adversely affected when the airplane is exposed to
high intensity radiated electromagnetic fields external to the
airplane.
2. For the purpose of these special conditions, 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.
Issued in Kansas City, Missouri on June 1, 1995.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-15889 Filed 6-27-95; 8:45 am]
BILLING CODE 4910-13-M
