[Federal Register Volume 64, Number 229 (Tuesday, November 30, 1999)]
[Rules and Regulations]
[Pages 66719-66721]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-31040]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE156, Special Condition 23-100-SC]


Special Conditions; Piper Cheyenne PA-31T2; Protection of Systems 
for High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued to Carpenter Avionics, 
Inc., 624-B Fitzhugh Blvd., Smyrna Airport, Smyrna, Tennessee 37167, 
for a Supplemental Type Certificate for the Piper Cheyenne PA-31T2 
airplane. 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 flight instrument system (EFIS) 
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.

DATES: The effective date of these special conditions is November 18, 
1999. Comments must be received on or before December 30, 1999.

ADDRESSES: Comments may be mailed in duplicate to: Federal Aviation 
Administration, Regional Counsel, ACE-7, Attention: Rules Docket Clerk, 
Docket No. CE156, Room 506, 901 Locust, Kansas City, Missouri 64106. 
All comments must be marked: Docket No. CE156. 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, 901 Locust, 
Room 301, Kansas City, Missouri 64106; telephone (816) 329-4123, or Les 
Taylor, Aerospace Engineer, at the same address, telephone (816) 329-
4134.

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, 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 
these special conditions 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 notice 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 conditions 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 notice must include a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Docket No. CE156.'' The postcard will be date stamped and 
returned to the commenter.

Background

    On June 25, 1999, Carpenter Avionics Inc., 624-B Fitzhugh Blvd., 
Smyrna Airport, Smyrna, Tennessee 37167, made an application to the FAA 
for a new Supplemental Type Certificate for the Piper Cheyenne PA-31T2 
airplane. The Cheyenne is currently approved under TC No. A8EA. The 
proposed modification incorporates a novel or unusual design feature, 
such as digital avionics consisting of an EFIS, that is vulnerable to 
HIRF external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR part 21, Sec. 21.101, Carpenter 
Avionics, Inc. must show that the Piper Cheyenne PA-31T2 aircraft meets 
the following provisions, or the applicable regulations in effect on 
the date of application for the change to the Cheyenne PA-31T2: CAR 3 
effective May 15, 1956, through Amendment 3-8, effective December 18, 
1962; FAR 23.205, 23.1545, 23.1563 and 23.1583, as amended by Amendment 
23-3, effective November 11, 1965; and FAR 23.1557(c) as amended by 
Amendment 23-7, effective September 14, 1969; and the Eastern Region 
Engineering and Manufacturing Branch letter of December 6, 1965, 
addressing the showing of equivalent safety with regard to CAR 3.682, 
3.771 and 3.772. Special Conditions No. 23-3-EA-1, Docket No. 9245, 
including Amendment No. 1 and AEA-210 letter of November 11, 1971, as 
amended by AEA-210 letter of February 1, 1978, referring to Amendment 
23-14 and FAR 23.991 as amended by Amendment 23-7, effective September 
14, 1969. Noise Certification--FAR 36 up to Amendment 10, as 
applicable. Fuel Venting Emissions--SFAR 27 up to Amendment 3, as 
applicable, and Sec. 23.1301 of Amendment 23-20; Secs. 23.1309, 
23.1311, and 23.1321 of Amendment 23-49; and Sec. 23.1322 of Amendment 
23-43; exemptions, if any; and the special conditions adopted by this 
rulemaking action.

Discussion

    If the Administrator finds that the applicable airworthiness 
standards 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.
    Special conditions are normally issued in accordance with 
Sec. 11.49, as required by Secs. 11.28 and 11.29(b), and become a 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 applicant apply for a supplemental type 
certificate to modify any other model already included on the same type 
certificate 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

    Carpenter Avionics Inc. 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 EFIS, 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

[[Page 66720]]

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 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 per
                       Frequency                              meter)
                                                        ----------------
                                                          Peak   Average
------------------------------------------------------------------------
10 kHz-100 kHz.........................................      50       50
100 kHz-500 kHz........................................      50       50
500 kHz-2 MHz..........................................      50       50
2 MHz-30 MHz...........................................     100      100
30 MHz-70 MHz..........................................      50       50
70 MHz-100 MHz.........................................      50       50
100 MHz-200 MHz........................................     100      100
200 MHz-400 MHz........................................     100      100
400 MHz-700 MHz........................................     700       50
700 MHz-1 GHz..........................................     700      100
1 GHz-2 GHz............................................    2000      200
2 GHz-4 GHz............................................    3000      200
4 GHz-6 GHz............................................    3000      200
6 GHz-8 GHz............................................    1000      200
8 GHz-12 GHz...........................................    3000      300
12 GHz-18 GHz..........................................    2000      200
18 GHz-40 GHz..........................................     600      200
------------------------------------------------------------------------
  The field strengths are expressed in terms of peak root-mean-square
(rms) values.
------------------------------------------------------------------------

      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 either electrical 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, similarity 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.

Applicability

    As discussed above, these special conditions are applicable to 
Piper Cheyenne PA-31T2 airplane. Should Carpenter Avionics Inc. apply 
at a later date for a supplemental type certificate to modify any other 
model on the same type certificate to incorporate 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 novel or unusual design features 
on one model of airplane. 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 airplane.
    The substance of these special conditions has been subjected to the 
notice and comment period 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 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 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 23

    Aircraft, Aviation safety, Signs and symbols.

Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR part 21, 
Secs. 21.16 and 21.101; and 14 CFR part 11, Secs. 11.28 and 11.49.

The 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 Piper Cheyenne PA-31T2 airplane 
modified by Carpenter Avionics Inc. to add an EFIS.
    1. Protection of Electrical and Electronic Systems from High 
Intensity Radiated Fields (HIRF). Each system

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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 November 18, 1999.
Marvin R. Nuss,
Acting Manager, Small Airplane Directorate.
[FR Doc. 99-31040 Filed 11-29-99; 8:45 am]
BILLING CODE 4910-13-P