[Federal Register Volume 68, Number 174 (Tuesday, September 9, 2003)]
[Rules and Regulations]
[Pages 53028-53030]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-22797]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM264, Special Conditions No. 25-246-SC]


Special Conditions: Gulfstream Aerospace LP 1125 Westwind Astra; 
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 Gulfstream Aerospace 
LP 1125 Westwind Astra airplanes modified by Garrett Aviation Services. 
These modified airplanes will have novel or unusual design features 
when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. The 
modification incorporates the upgrade of one Air Data Computer system 
and the installation of a second Air Data Computer system, both of 
which perform critical functions. The applicable airworthiness 
regulations do not contain adequate or appropriate safety 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 that provided by the existing 
airworthiness standards.

DATES: The effective date of these special conditions is August 28, 
2003. Comments must be received on or before October 9, 2003.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Attention: Rules Docket (ANM-113), Docket No. NM264, 1601 
Lind Avenue SW., Renton, Washington 98055-4056; or delivered in 
duplicate to the Transport Airplane Directorate at the above address. 
All comments must be marked: Docket No. NM264.

FOR FURTHER INFORMATION CONTACT: Meghan Gordon, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(425) 227-2138; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that notice and opportunity for prior public 
comment is impracticable, because these procedures would significantly 
delay certification of the airplane 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; however, the FAA invites interested persons to participate in 
this rulemaking by submitting written comments, data, or views. The 
most helpful comments reference a specific portion of the special 
conditions, explain the reason for any recommended change, and include 
supporting data. We ask that you send us two copies of written 
comments.
    We will file in the docket all comments we receive as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. The docket is available for public 
inspection before and after the comment close date. If you wish to 
review the docket in person, go to the address in the ADDRESSES section 
of this preamble between 7:30 a.m. and 4 p.m., Monday through Friday, 
except Federal holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late, if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions, based on the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, include with your comments a pre-addressed, 
stamped postcard on which the docket number appears. We will stamp the 
date on the postcard and mail it back to you.

Background

    On July 2, 2003, Garrett Aviation Services, 1200 North Airport 
Drive, Capital Airport, Springfield, IL 62707, applied for a 
supplemental type certificate (STC) to modify Gulfstream Aerospace LP 
Model 1125 Westwind Astra airplanes approved under Type Certificate No. 
A16NM. The Model 1125 Westwind Astra is a small transport category 
airplane, powered by two Turbofan Engines; the airplane has a maximum 
takeoff weight of 24,800 pounds. The Model 1125 Westwind Astra operates 
with a 2-pilot crew and holds up to 9 passengers. The modification 
incorporates the upgrade

[[Page 53029]]

of the single Rockwell Collins ADS-85 Air Data System and the 
installation of an Innovative Solutions & Support Air Data Display Unit 
and a 2-inch Standby Altimeter. These avionics/ electronics and 
electrical systems have the potential to be vulnerable to high-
intensity radiated fields (HIRF) external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Garrett Aviation Services 
must show that the Model 1125 Westwind Astra airplanes, as modified, 
continue to meet the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A16NM 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 Model 1125 
Westwind Astra airplanes includes 14 CFR part 25, dated February 1, 
1965, through Amendment 25-54, except for special conditions and 
exceptions noted in Type Certificate Data Sheet (TCDS) A16NM.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for the Gulfstream Aerospace LP Model 1125 
Westwind Astra airplanes modified by Garrett Aviation Services 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, the Gulfstream Aerospace LP 1125 Westwind Astra airplanes 
modified by Garrett Aviation Services must comply with the fuel vent 
and exhaust requirements of 14 CFR part 34 and the noise certification 
requirements of 14 CFR part 36, and the FAA must issue a finding of 
regulatory adequacy pursuant to Sec.  611 of Public Law 92-574, the 
``Noise Control Act of 1972.''
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with Sec.  11.38, and become part of the type certification 
basis in accordance with Sec.  21.101.
    Special conditions are initially applicable to the model for which 
they are issued. Should Garrett Aviation Services apply at a later date 
for a supplemental type certificate to incorporate the same or similar 
novel or unusual design features, these special conditions would also 
apply to the other model.

Novel or Unusual Design Features

    As noted earlier, the Gulfstream Aerospace LP Model 1125 Westwind 
Astra airplanes modified by Garrett Aviation Services will incorporate 
the upgrade of the single Rockwell Collins ADS-85 Air Data System and 
the installation of an Innovative Solutions & Support Air Data Display 
Unit and a 2-inch Standby Altimeter that will perform critical 
functions. These systems may be vulnerable to HIRF external to the 
airplane. The current airworthiness standards of part 25 do not contain 
adequate or appropriate safety standards for the protection of this 
equipment from the adverse effects of HIRF. Accordingly, these systems 
are considered to be a novel or unusual designs.

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 avionics/electronics 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 reference, special 
conditions are needed for the Gulfstream Aerospace LP Model 1125 
Westwind Astra airplanes modified by Garrett Aviation Services. These 
special conditions require that new avionics/electronics and electrical 
systems 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 and the advent of space and satellite communications, 
coupled with electronic command and control of the airplane, the 
immunity of critical avionics/electronics 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 2 below:
    1. A minimum threat of 100 volts rms (root-mean-square) 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 field strengths 
identified in the table below for the frequency ranges indicated. Both 
peak and average field strength components from the table are to be 
demonstrated.

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                                            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             200
2GHz-4 GHz..............................            3000             200
4 GHz-6 GHz.............................            3000             200

[[Page 53030]]

 
6 GHz-8 GHz.............................            1000             200
8 GHz-12 GHz............................            3000             300
12 GHz-18 GHz...........................            2000             200
18 GHz-40 GHz...........................             600            200
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Note.--The field strengths are expressed in terms of peak of the root-
  mean-square (rms) values over the complete modulation period.

    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 
Gulfstream Aerospace LP Model 1125 Westwind Astra airplanes modified by 
Garrett Aviation Services. Should Garrett Aviation Services apply at a 
later date for a supplemental type certificate to modify any other 
model included on the Type Certificate No. A16NM to incorporate the 
same or similar novel or unusual design features, these special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on Gulfstream Aerospace LP Model 1125 Westwind Astra airplanes modified 
by Garrett Aviation Services. It is not a rule of general applicability 
and affects only the applicant which applied to the FAA for approval of 
these features on the airplanes.
    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. 
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 record keeping 
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 Gulfstream Aerospace LP Model 1125 
Westwind Astra airplanes modified by Garrett Aviation Services.
    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.
    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.

Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-22797 Filed 9-8-03; 8:45 am]
BILLING CODE 4910-13-P