[Federal Register Volume 60, Number 185 (Monday, September 25, 1995)]
[Rules and Regulations]
[Pages 49331-49333]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-23732]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-117; Special Condition No. 25-ANM-107]


Special Condition: Boeing Model 727-100, High-Intensity Radiated 
Fields

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special condition, request for comments.

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[[Page 49332]]


SUMMARY: This special condition is issued for the Boeing Model 727-100 
airplane. This airplane, as modified by Associated Air Center, utilizes 
new avionics/electronic systems, such as the electronic flight 
information systems (EFIS), which perform critical functions. The 
applicable regulations do not contain adequate or appropriate safety 
standards for the protection of these systems from the effects of high-
intensity radiated fields (HIRF). This special condition contains the 
additional safety standards that the Administrator considers necessary 
to establish a level of safety equivalent to that established by the 
existing airworthiness standards.

DATES: The effective date of this special condition is September 14, 
1995. Comments must be received on or before October 25, 1995.

ADDRESSES: Comments on this special condition may be mailed in 
duplicate to: Federal Aviation Administration, Office of the Assistant 
Chief Counsel, Attn: Rules Docket (ANM-7), Docket No. NM-117, 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-117. 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:
Tim Backman, FAA, Standardization Branch, ANM-113, Transport Airplane 
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington, 98055-4056; telephone (206) 227-2797; facsimile 
(206) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that good cause exists for making this 
special condition 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 condition 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. This special 
condition 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-117.'' The postcard will 
be date stamped and returned to the commenter.

Background

    On May 16, 1995, Associated Air Center (AAC), PO Box 54078, Dallas, 
Texas 75354, applied for a Supplemental Type Certificate (STC) to 
incorporate changes to the Boeing Model 727-100 airplane. The proposed 
modification includes the installation of digital avionics, including 
an Electronic Flight Instrument System (EFIS), which is vulnerable to 
high-intensity radiated fields (HIRF) external to the airplane.
    Boeing Model 727-100 series airplanes are listed on Type 
Certificate (TC) A3WE. The airplanes are pressurized, 131 passenger, 
large commercial transport type airplanes having a maximum operating 
altitude of 42,000 feet. The airplanes are powered by three aft 
fuselage-mounted turbojet or turbofan engines, depending on the 
specific model and airplane configuration.

Type Certification Basis

    Under the provision of Sec. 21.101 of 14 CFR part 21, AAC must show 
that the modified Boeing 727-100 continues to meet the applicable 
provisions of the regulations incorporated by reference in TC A3WE, 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 TC 
A3WE are as follows: CAR 4b, dated December 31, 1953, including 
Amendments 4b-1 thru 4b-11, and Special CAR SR-422B. In addition, the 
certification basis includes Sec. 25.1316, as added by Amendment 25-80, 
and may also include exemptions and other special conditions that are 
not relevant to this special condition. This special condition will 
form an additional part of the 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 Boeing Model 727-100 
series airplanes because of a novel or 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).

Novel or Unusual Design Features

    The Boeing Model 727-100 incorporates new avionic/electronic 
systems, such as the electronic flight instrument system (EFIS), that 
perform critical functions. These systems may be vulnerable to HIRF 
external to the airplane.

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 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, a special 
condition is needed for the Boeing Model 727-100, as modified by AAC, 
which requires that new electrical and electronic 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, plus the advent of space and satellite communications, 
coupled with electronic command and control of the airplane, the 
immunity of critical digital avionics 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 

[[Page 49333]]
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:
    1. A minimum threat of 100 volts per meter peak 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:

------------------------------------------------------------------------
                                                                        
                       Fequency                         Peak (V/ Average
                                                           M)     (V/M) 
------------------------------------------------------------------------
10 KHz-100 KHz........................................       50       50
100 KHz-500 KHz.......................................       60       60
500 KHz-2 MHz.........................................       70       70
2 MHz-30 MHz..........................................      200      200
30 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-1 GHz.........................................    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, this special condition is applicable to the 
Boeing Model 727-100 airplane, as modified by AAC. Should AAC apply at 
a later date for a supplemental type certificate to modify any other 
model included on Type Certificate No. A3WE to incorporate the same 
novel or unusual design feature, this special condition would apply to 
that model as well, under the provisions of Sec. 21.101(a)(1).

Conclusion

    This action affects only certain design features on the Boeing 
Model 727-100 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 the special condition for this airplane 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 this special 
condition immediately. Therefore, this special condition is 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 this special condition is as follows:

    Authority: 49 U.S.C. app. 1344, 1354(a), 1355, 1421, 1423, 1424, 
1425, 1428, 1429, 1430, and 49 U.S.C. 106(g).

The Special Condition

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special condition is issued as part of the 
type certification basis for the Boeing Model 727-100, as modified by 
Associated Air Center.
    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 this special condition, 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, WA, on September 14, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-23732 Filed 9-22-95; 8:45 am]
BILLING CODE 4910-13-M