[Federal Register Volume 66, Number 209 (Monday, October 29, 2001)]
[Rules and Regulations]
[Pages 54414-54416]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-27160]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM200; Special Conditions No. 25-189-SC]


Special Conditions: Boeing Model 727-100/-200 Series Airplanes; 
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 Boeing Model 727 -100/
-200 series airplanes modified by Aircraft Systems & Manufacturing. 
These modified airplanes will have a novel or unusual design feature 
when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. The 
modification incorporates the installation of new electronic air data 
systems that 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 established by the 
existing airworthiness standards.

DATES: The effective date of these special conditions is October 19, 
2001. Comments must be received on or before November 28, 2001.

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. NM200, 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. NM200. 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: 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:
    The FAA has determined that notice and opportunity for prior public 
comment hereon are 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.

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 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. NM200.'' The postcard will be date stamped and returned 
to the commenter.

Background

    On June 5, 2001, Aircraft Systems & Manufacturing, Georgetown, 
Texas, applied for a Supplemental Type Certificate (STC) to modify 
Boeing Model 727-100/-200 series airplanes. These airplanes are low-
wing, pressurized transport category airplanes with three fuselage-
mounted jet engines. They are capable of seating between 120 and 189 
passengers, depending upon the model and configuration. The 
modification incorporates the installation of new electronic air data 
systems consisting of a single air data computer, electronic altimeter 
for display of No. 1 altitude data and an air data display unit for 
display of No. 2 altitude data. These systems have a 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, Aircraft Systems & 
Manufacturing must show that the Boeing Model 727-100/-200 series 
airplanes, as modified to include the new electronic air data systems, 
continue to meet the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A3WE or the 
applicable regulations in effect on the date of

[[Page 54415]]

application for the change. The regulations incorporated by reference 
in the type certificate are commonly referred to as the ``original type 
certification basis.'' The specific regulations included in the 
certification basis for the Boeing Model 727-100/-200 series airplanes 
include Civil Air Regulations (CAR) 4b, as amended by amendment 4b-1 
through 4b-11.
    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 Boeing Model 727-100/-200 series 
airplanes because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec. 21.16.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49, as required by Secs. 11.28 and 11.29, and become part of 
the airplane's 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 Aircraft Systems & Manufacturing 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 also 
apply to the other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    As noted earlier, the Boeing 727-100/-200 series airplanes modified 
by Aircraft Systems & Manufacturing will incorporate new electronic air 
data systems that will perform critical functions. These systems may be 
vulnerable to high-intensity radiated fields 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 design features.

Discussion

    There is no specific regulation that addresses requirements for 
protection of 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 that is equivalent to 
that intended by the regulations incorporated by reference, special 
conditions are needed for the Boeing Model 727-100/-200 series 
airplanes modified by Aircraft Systems & Manufacturing. These special 
conditions will require that these systems, which perform critical 
functions, must 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 on 
surveys and analysis of existing HIRF emitters, an adequate level of 
protection exists when compliance with the HIRF protection special 
condition is shown in accordance with either paragraph 1 OR 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
------------------------------------------------------------------------
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
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.

    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 the 
Boeing Model 727 -100/-200 series airplanes modified by Aircraft 
Systems & Manufacturing to install new electronic air data systems. 
Should Aircraft Systems & Manufacturing apply at a later date for a 
design change approval to modify any other model included on Type 
Certificate A3WE 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 design features on the Boeing 
Model 727 -100/-200 series airplanes modified by Aircraft Systems & 
Manufacturing to include the new electronic air data systems. 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 airplanes.
    The substance of the special conditions for these airplanes 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.

[[Page 54416]]

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 supplemental type certification basis for the Boeing Model 727-100/
-200 series airplanes as modified by Aircraft Systems & Manufacturing.
    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.

    Issued in Renton, Washington, on October 19, 2001.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-27160 Filed 10-26-01; 8:45 am]
BILLING CODE 4910-13-P