[Federal Register Volume 60, Number 115 (Thursday, June 15, 1995)]
[Rules and Regulations]
[Pages 31384-31386]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-14660]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-110; Special Conditions No. 25-ANM-100]


Special Conditions: Modified Gulfstream American Corporation 
Model 1159 Airplane; High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Gulfstream 
American Corporation (GAC) Model 1159 airplane, modified by Learjet, 
Inc., of Denver, Colorado. This airplane will be 
[[Page 31385]] equipped with a digital Electronic Flight Instrument 
System (EFIS) that will perform critical functions. The applicable 
regulations do not contain adequate or appropriate safety standards for 
the protection of the EFIS from the effects of high-intensity radiated 
fields (HIRF). These special conditions provide the additional safety 
standards that the Administrator considers necessary to ensure that the 
critical functions performed by this system are maintained when the 
airplane is exposed to HIRF.

DATES: The effective date of these special conditions is May 26, 1995. 
Comments must be received on or before July 31, 1995.

ADDRESSES: Comments on these final special conditions, request for 
comments, may be mailed in duplicate to: Federal Aviation 
Administration, Office of the Assistant Chief Counsel, Attn: Rules 
Docket (ANM-7), Docket No. NM-110, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056; or delivered in duplicate to the Office of the 
Assistant Chief Counsel at the above address. Comments must be marked 
``Docket No. NM-110.'' Comments may be inspected in the Rules Docket 
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT:
Mark Quam, FAA, Standardization Branch, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington 98055-4056; telephone (206) 227-2145.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that good cause exists for making these 
special conditions effective upon issuance; however, 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 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. Persons wishing the FAA to acknowledge receipt of their 
comments submitted in response to this request must submit with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket No. NM-110.'' The postcard will 
be date stamped and returned to the commenter.

Background

    On March 27, 1995, Learjet, Inc., of Denver, Colorado, applied for 
a supplemental type certificate to modify the Gulfstream American 
Corporation (GAC) Model 1159 airplane. The GAC Model 1159 airplane is a 
business jet with two aft-mounted turbofan engines. The airplane can 
carry two pilots and 19 passengers, depending on the exit and interior 
configuration, and is capable of operating to an altitude of 45,000 
feet. The original equipment installed in these airplanes presented the 
required flight information in the form of analog displays. The 
proposed modification incorporates the installation of a five tube 
digital Electronic Flight Instrument System (EFIS) that displays 
required flight critical information and critical functions. The 
installation of the EFIS system displaying critical functions is 
potentially vulnerable to high-intensity radiated fields (HIRF) 
external to the airplane.

Supplemental Type Certification Basis

    Under the provisions of Sec. 21.101 of the Federal Aviation 
Regulations (FAR), Learjet, Inc., must show that the altered GAC Model 
1159 airplane continues to meet the applicable provisions of the 
regulations incorporated by reference in Type Certificate No. A12EA, or 
the applicable regulations in effect on the date of application for the 
change. 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 Type Certificate No. 
A12EA include the following for the GAC Model 1159 airplanes: Civil 
Aviation Regulation (CAR) 4b dated December 31, 1953, including 
Amendments 4b-1 through 4b-14, Special Regulations SR422B and SR450A. 
In addition, under Sec. 21.101(b)(1), the following sections of the FAR 
apply to the EFIS installation: 25.1301(d), 25.1303, and 25.1322, as 
amended by Amendment 25-38; and 25.1309, 25.1321(a)(b)(d), and (e), 
25.1331, 25.1333, and 25.1335, as amended by Amendment 25-41. These 
special conditions will form an additional part of the supplemental 
type certification basis.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., CAR 4b or part 25, as amended) do not contain 
adequate or appropriate safety standards for the GAC Model 1159 
airplane because of a novel of 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 of the FAR after public notice, as required by Secs. 11.28 
and 11.29, 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 applicant apply for a supplemental type 
certificate to modify any other model 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).

Discussion

    There is no specific regulation that addresses protection 
requirements for electrical and electric systems from high-intensity 
radiated fields (HIRF). Increased power levels from ground-based radio 
transmitters, and the growing use of sensitive electrical and 
electronic systems to command and control airplanes, have made it 
necessary to provide adequate protection.
    To ensure that a level of safety is achieved equivalent to that 
intended by the regulations incorporated by reference, special 
conditions are needed for the modified GAC Model 1159 airplanes that 
would require that the EFIS be designed and installed to preclude 
component damage and interruption of function due to the effects of 
HIRF.
    With the trend toward increased power levels from ground-based 
transmitters, plus the advent of space and satellite communications, 
coupled with electronic command and control of the airplane, the 
immunity of critical digital avionics systems, such as the EFIS, to 
HIRF must be established.
    It is not possible to precisely define the HIRF to which the 
airplanes will be exposed in service. There is also uncertainty 
concerning the effectiveness of airframe shielding for HIRF. 
Furthermore, coupling of electromagnetic energy to cockpit-installed 
equipment through the cockpit window apertures is undefined. Based on 
surveys and analysis of existing HIRF emitters, an adequate level of 
protection exists when compliance with the HIRF protection special 
condition is shown with either paragraphs 1 or 2 below: [[Page 31386]] 
    1. A minimum threat of 100 volts per meter peak electric field 
strength from 10 KHz to 18 GHz.
    a. The treat must be applied to the system elements and their 
associated wiring harnesses without the benefit of airframe shielding.
    b. Demonstration of this level of protection is established through 
system tests and analysis.
    2. A threat external to the airframe of the following field 
strengths for the frequency ranges indicated:

------------------------------------------------------------------------
                                                      Peak (V/   Average
                      Frequency                          M)       (V/M) 
------------------------------------------------------------------------
10 KHz-100 KHz......................................        50        50
100 KHz-500 KHz.....................................        60        60
500 KHz-2000 KHz....................................        70        70
2 MHz-30 MHz........................................       200       200
30 MHz-70 MHz.......................................        30        30
70 MHz-100 MHz......................................        30        30
100 MHz-200 MHz.....................................       150        33
200 MHz-400 MHz.....................................        70        70
400 MHz-700 MHz.....................................     4,020       935
700 MHz-1000 MHz....................................     1,700       170
1 GHz-2 GHz.........................................     5,000       990
2 GHz-4 GHz.........................................     6,680       840
4 GHz-6 GHz.........................................     6,850       310
6 GHz-8 GHz.........................................     3,600       670
8 GHz-12 GHz........................................     3,500     1,270
12 GHz-18 GHz.......................................     3,500       360
18 GHz-40 GHz.......................................     2,100       750
------------------------------------------------------------------------

    As discussed above, these special conditions are applicable to the 
GAC Model 1159 airplane, modified by Learjet, Inc. Should Learjet, Inc. 
apply at a later date for a supplemental type certificate to modify any 
other model included on Type Certificate No. A12EA 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 unusual or novel design features 
on GAC Model 1159 airplanes modified by Learjet, Inc. It is not a rule 
of general applicability and affects only the applicant who applied to 
the FAA for approval of this feature on this airplane.
    The substance of these special conditions 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 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 immediately. Therefore these special 
conditions are 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 the prior opportunities for 
comment described above.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority. 49 U.S.C. app. 1344, 1348(c), 1352, 1354(a), 1355, 
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et 
seq.; E.O. 11514; and 49 U.S.C. 106(g).

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the supplemental type certification basis for the GAC Model 1159 
airplane, as modified by Learjet, Inc.:
    1. Protection from Unwanted Effects of High-Intensity Radiated 
Fields (HIRF). Each electrical and electronic system that performs 
critical functions must be designed and installed to ensure that the 
operation and operational capability of these systems to perform 
critical functions are not adversely affected when the airplane is 
exposed to high intensity radiated fields external to the airplane.
    2. The following definition applies with respect to this special 
condition: Critical Function. 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 Renton, Washington, on May 26, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-14660 Filed 6-14-95; 8:45 am]
BILLING CODE 4910-13-U