[Federal Register Volume 63, Number 57 (Wednesday, March 25, 1998)]
[Proposed Rules]
[Pages 14381-14383]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-7826]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM147; Notice No. 25-98-02-SC]


Special Conditions: Boeing Model 757-300; High-Intensity Radiated 
Fields

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for the Boeing Model 
757-300. This airplane will utilize new avionics/electronic systems 
that provide critical data to the flightcrew. 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. These proposed special conditions contain 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: Comments must be received on or before April 24, 1998.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Office of the Regional Counsel, Attn: 
Rules Docket (ANM-7), Docket No. NM147, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056; or delivered in duplicate to the Office of the 
Regional Counsel at the above address. Comments must be marked: Docket 
No. NM147. 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: John Dimtroff, FAA, Airplane and 
Flight Crew Interface Branch, ANM-111, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056, telephone (425) 227-2117 or facsimile (425) 
227-1320.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of 
these proposed special conditions by submitting 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 
before further rulemaking action on this proposal is taken. The 
proposals contained in this notice may be changed in light of the 
comments received. All comments received will be available, both before 
and after the closing date for comments, in the Rules Docket for 
examination by interested parties. 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. NM147.'' The

[[Page 14382]]

postcard will be date stamped and returned to the commenter.

Background

    On February 21, 1996, the Boeing Commercial Airplane Group, P. O. 
Box 3707, Seattle, Washington 98124-2207, applied for an amendment to 
Type Certificate No. A2NM to include the new Model 757-300, a 
derivative of the 757-200. The 757-300 is a swept-wing, conventional-
tail, twin-engine, turbofan-powered transport. Each engine will be 
capable of delivering 43,100 pounds of thrust. The flight controls are 
unchanged beyond those changes deemed necessary to accommodate the 
stretched configuration. The airplane has a seating capacity of up to 
289, and a maximum takeoff weight of 270,000 pounds (122,470 Kg).

Type Certification Basis

    Under the provisions of Title 14 CFR 21.101, Boeing must show that 
the Model 757-300 meets the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A2NM, or the 
applicable regulations in effect on the date of application for the 
change to the Model 757-300. 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. A2NM include 14 CFR part 25, as amended by 
Amendments 25-1 through 25-45, and certain other later amended sections 
of part 25 that are not relevant to these proposed special conditions. 
Except for certain earlier amended sections of part 25 that are not 
relevant to these proposed special conditions, Boeing has chosen to 
comply with part 25 as amended by Amendments 25-1 through 25-85, the 
applicable regulations in effect on the date of application. In 
addition to the applicable airworthiness regulations and special 
conditions, the 757-300 must comply with the fuel vent and exhaust 
emission requirements of part 34, effective September 10, 1990, plus 
any amendments in effect at the time of certification; and the noise 
certification requirements of part 36, effective December 1, 1969, as 
amended by Amendment 36-1 through the amendment in effect at the time 
of certification. The special conditions that may be developed as a 
result of this notice will form an additional part of the type 
certification basis.
    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 757-300 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(b), 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 type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified 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 757-300 airplane avionics enhancement will utilize electronic 
systems that perform critical functions, including the following 
airframe Line Replaceable Units (LRU): Multi-Mode Receiver (MMR), 
Flight Control Computer (FCC), Yaw Damper Stabilizer Trim Module (YSM), 
Air Data Inertial Reference System (ADIRS), and the Allied Signal Radio 
Altimeter (RA). These systems may be vulnerable to high-intensity 
radiated fields (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, special 
conditions are needed for the 757-300, which require that new 
technology electrical and electronic systems, such as the MMR, FCC, 
YSM, ADIRS, and RA, 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

    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 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.

----------------------------------------------------------------------------------------------------------------
                                                                      Field Strength (volts per meter)          
                                                           -----------------------------------------------------
                         Frequency                                 US            UK/European      Consolidated  
                                                           -----------------------------------------------------
                                                              Peak     Avg.     Peak     Avg.     Peak     Avg. 
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10 kHz-100 kHz............................................       30       30       50       50       50       50
100 kHz-500 kHz...........................................       40       30       60       60       60       60
500 kHz-2 MHz.............................................       30       30       70       70       70       70
2 MHz-30 MHz..............................................      190      190      200      200      200      200
30 MHz-70 MHz.............................................       20       20       30       30       30       30
70 MHz-100 MHz............................................       20       20       30       30       30       30

[[Page 14383]]

                                                                                                                
100 MHz-200 MHz...........................................       30       30      150       30      150       30
200 MHz-400 MHz...........................................       30       30       70       70       70       70
400 MHz-700 MHz...........................................       80       80      700       40      700       80
700 MHz-1 GHz.............................................      690      240     1700       80     1700      240
1 GHz-2 GHz...............................................      970       70     5000      360     5000      360
2 GHz-4 GHz...............................................     1570      350     4500      360     4500      360
4 GHz-6 GHz...............................................     7200      300     5200      300     7200      300
6 GHz-8 GHz...............................................      130       80     2000      330     2000      330
8 GHz-12 GHz..............................................     2100       80     3500      270     3500      270
12 GHz-18 GHz.............................................      500      330     3500      180     3500      330
18 GHz-40 GHz.............................................      780       20    (\1\)    (\1\)      780      20 
----------------------------------------------------------------------------------------------------------------
\1\ NA.                                                                                                         
The field strengths are expressed in terms of peak root-mean-square (rms) values.                               

    The threat levels identified above differ from those used in 
previous special conditions and 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. In general, these standards are 
less critical than the threat level that was previously used as the 
basis for earlier special conditions.

Applicability

    As discussed above, these special conditions would be applicable 
initially to the 757-300 airplane. Should Boeing apply at a later date 
for a change to the type certificate to include another model 
incorporating 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 certain design features only on the Model 757-
300. It is not a rule of general applicability and affects only the 
manufacturer who applied to the FAA for approval of these features on 
this model.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and record keeping 
requirements.

    The authority citation for these proposed special conditions is as 
follows:

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

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for the Boeing 757-300 series airplanes.
    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, Washington, on March 17, 1998.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-7826 Filed 3-24-98; 8:45 am]
BILLING CODE 4910-13-P