[Federal Register Volume 66, Number 87 (Friday, May 4, 2001)]
[Rules and Regulations]
[Pages 22428-22431]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-11253]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM191, Special Conditions No. 25-179-SC]


Special Conditions: Lockheed-Georgia Model 1329-25; and Models 
1329-23A, -23D and -23E airplanes modified by STC SA2326SW (JetStar 
731); 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 for the Lockheed-Georgia 
Model 1329-25, and Models 1329-23A, -23D and -23E airplanes modified by 
STC SA2326SW, for the modifications installed by Duncan Aviation Inc. 
These modified airplanes will have novel and unusual design features 
when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. The

[[Page 22429]]

modification incorporates the installation of dual Attitude Heading 
Reference Systems (ARHS) that provide input to both pilot and copilot 
flight instruments displaying critical flight parameters (attitude) to 
the flightcrew. The applicable airworthiness standards do not contain 
adequate or appropriate safety standards for the protection of these 
systems from the effects of high-intensity radiated fields (HIRF). The 
special conditions contain the additional safety standards that the 
Administrator considers necessary to establish a level of safety 
equivalent to that provided by the existing airworthiness standards.

DATES: The effective date of these special conditions is April 17, 
2001. Comments must be received on or before June 4, 2001.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Attn: Rules Docket (ANM-114), Docket No. NM191, 1601 Lind 
Avenue SW., Renton, Washington, 98055-4056; or delivered in duplicate 
to the Transport Airplane Directorate at the above address. Comments 
must be marked: Docket No. NM191. 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, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; 
telephone (425) 227-2145; facsimile (425) 227-1149.

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 Docket or 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 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 these special conditions must include 
a self-addressed, stamped postcard on which the following statement is 
made: ``Comments to Docket No. NM191.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On February 21, 2001, Duncan Aviation, Inc., P.O. Box 81887, 
Lincoln, Nebraska, applied for a supplemental type certificate (STC) to 
modify the Lockheed-Georgia Model 1329-25, and Models 1329-23A, -23D 
and -23E airplanes modified by STC SA2326SW, listed on Type Certificate 
2A15. These airplanes are four engine transport category airplanes of 
the executive type, capable of carrying two flight crewmembers and ten 
passengers. All models are powered by four aft mount AiResearch TFD-731 
engines. In the Model 1329-23A, -23D, and -23E airplanes modified by 
STC SA232SW, the Pratt & Whitney turbojet engines have been replaced 
with the AiResearch TFE-731 engines. The modification incorporates the 
installation of dual Rockwell Collins Attitude Heading Reference 
Systems (ARHS) that provide input to both pilot and copilot flight 
instruments displaying critical flight parameters (attitude and 
heading) to the flightcrew. The AHRS can be susceptible to disruption 
to both command/response signals as a result of electrical and magnetic 
interference. This disruption of signals could result in loss of all 
critical flight displays and annunciations or present misleading 
information to the pilot.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Duncan Aviation, Inc., must 
show that the Lockheed-Georgia Model 1329-25, and Models 1329-23A, -23D 
and -23E airplanes modified by STC SA2326SW, as changed, continue to 
meet the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. 2A15, 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 certification 
basis for the modified Lockheed-Georgia Model 1329-25, and Models 1329-
23A, -23D and -23E airplanes modified by STC SA2326SW, includes CAR 4b, 
dated December 31, 1953, as amended by Amendments 4b-1 through 4b-9 as 
listed in the Type Certificate Data Sheet (TCDS) 2A15.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., CAR 4b, as amended) do not contain adequate or 
appropriate safety standards for the Lockheed-Georgia Model 1329-25, 
and Models 1329-23A, -23D and -23E airplanes modified by STC SA2326SW, 
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, these Lockheed-Georgia Model 1329-25; and Models 1329-23A, 
-23D, and -23E airplanes must comply with the fuel vent and exhaust 
emission requirements of part 34 and the noise certification 
requirements of part 36.
    Special conditions, as defined in Sec. 11.19, are issued in 
accordance with Sec. 11.38 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 Duncan apply at a later date 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, these special conditions would also apply to the other model 
under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    As noted earlier, the modified Lockheed-Georgia Model 1329-25, and 
Models 1329-23A, -23D and -23E airplanes modified by STC SA2326SW, will 
incorporate dual Attitude and Heading Reference Systems (AHRS) that 
provide input to both pilot and copilot flight instruments displaying 
critical flight parameters (attitude and heading) to the flightcrew. 
The AHRS can be susceptible to disruption to both command/response 
signals as a result of electrical and magnetic interference. This 
disruption of signals could result in loss of all critical flight 
displays and annunciations or present misleading information to the 
pilot.

Discussion

    There is no specific regulation that addresses protection 
requirements for electrical and electronic systems from HIRF. Increased 
power levels from ground-based radio transmitters and the growing use 
of sensitive avionic/electronic and electrical 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

[[Page 22430]]

reference, special conditions are needed for the Lockheed-Georgia Model 
1329-25; and Models 1329-23A, -23D and -23E. These special conditions 
require that new avionic/electronic and electrical systems, such as the 
AHRS, that perform critical functions be designed and installed to 
preclude component damage and interruption of function due to both the 
direct and indirect effects of HIRF.

High-Intensity Radiated Fields (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 avionic/electronic and electrical systems to HIRF 
must be established.
    It is not possible to precisely define the HIRF to which the 
airplane 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 paragraph 1, or paragraph 2, below:
    1. A minimum threat of 100 volts rms per meter electric field 
strength from 10 KHz to 18 GHz.
    a. The threat 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. Both peak and average 
field strength components from the Table are to be demonstrated.

------------------------------------------------------------------------
                                             Field strength (volts per
                                                      meter)
                Frequency                -------------------------------
                                               Peak           Average
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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              20
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 of the root-mean-
 square (rms) over the complete modulation period.
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    The threat levels identified above are the result of an FAA review 
of existing studies on the subject of HIRF, in light of the ongoing 
work of the Electromagnetic Effects Harmonization Working Group of the 
Aviation Rulemaking Advisory Committee.

Applicability

    As discussed above, these special conditions are applicable to 
Lockheed-Georgia Model 1329-25, and Models 1329-23A, -23D and --23E 
airplanes modified by STC SA2326SW, with the modifications installed by 
Duncan Aviation. Should Duncan Aviation apply at a later date 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, these 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 Lockheed-Georgia Model 1329-25, and Models 1329-23A, -23D and -23E 
airplanes modified by STC SA2326SW, that are further modified by Duncan 
Aviation. 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 the special conditions for this airplane 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 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

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 Lockheed-Georgia Model 1329-25, and 
Models 1329-23A, -23D and -23E airplanes modified by STC SA2326SW, that 
are further modified by Duncan Aviation, 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

[[Page 22431]]

to perform critical functions are not adversely affected when the 
airplane is exposed to high intensity radiated fields.
    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 Renton, Washington, on April 17, 2001.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-11253 Filed 5-3-01; 8:45 am]
BILLING CODE 4910-13-U