[Federal Register Volume 64, Number 139 (Wednesday, July 21, 1999)]
[Rules and Regulations]
[Pages 38999-39001]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-18566]
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Rules and Regulations
Federal Register
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Federal Register / Vol. 64, No. 139 / Wednesday, July 21, 1999 /
Rules and Regulations
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM159; Special Conditions No. 25-145-SC]
Special Conditions: Boeing Model 707-353B (USAF C-137) Airplanes;
High Intensity Radiated Fields (HIRF) Protection
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 707-353B
(USAF C-137) airplanes. These airplanes will have novel and unusual
design features when compared to the state of technology envisioned in
the airworthiness standards for transport category airplanes. These
design features include the installation of an inertial navigation
system (INS) for which the current applicable airworthiness regulations
do not contain adequate or appropriate safety standards with regard to
protection of the system from the effects of high-intensity radiated
fields. 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 July 13, 1999.
Comments must be received on or before August 20, 1999.
ADDRESSES: Comments on these special conditions may be mailed in
duplicate to: Federal Aviation Administration, Transport Airplane
Directorate, Attention: Rules Docket (ANM-114), Docket No. NM159, 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. NM159. 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: Mark Quam, FAA, Standardization
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone
(425) 227-2799; facsimile (425) 227-1149.
SUPPLEMENTARY INFORMATION:
FAA's Determination as to Need for Public Process
The FAA has determined that notice and opportunity for prior public
comment hereon are impracticable because those procedures would
significantly delay issuance of the approval design and, thus, the
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. Thus, the FAA has previously provided
the public with a number of opportunities to comment on proposed
special conditions that are substantively identical to those at issue;
and the FAA is reasonably assured that all interested members of the
public have had an opportunity to comment and that their comments have
been fully considered. The FAA, therefore, finds that additional
redundant notices are unnecessary, and good cause exists for making
these special conditions effective upon issuance.
Comments Invited
Although this action is in the form of final special conditions
and, for the reasons stated above, is not preceded by notice and an
opportunity for public comment, comments are invited on this rule.
Interested persons are invited to submit 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. The
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 this notice must include a self-
addressed, stamped postcard on which the following statement is made:
``Comments to Docket NM159.'' The postcard will be date stamped and
returned to the commenter.
Background
On August 7, 1998, Boeing Commercial Airplane Group, P.O. Box 7730,
Wichita, Kansas 67277, made application to the FAA for a Supplemental
Type Certificate(STC) for the Boeing Model B-707-353B airplane [known
as the U.S. Air Force (USAF) C-137]. The proposed configuration of this
model will incorporate an upgrade of the inertial navigation system
(INS) from the Litton LTN-72 model to the LTN-92 model.
The INS provides attitude, heading, and navigation data to the
flight crew. Display of attitude information is considered a critical
function. Critical functions must be designed and installed to ensure
that their operations are not adversely affected by high intensity
radiated fields (HIRF). The existing airworthiness regulations do not
contain adequate or appropriate safety standards for protection from
the effects of HIRF external to the airplane; therefore, a special
condition is proposed.
Supplemental Type Certification Basis
Under the provisions of 14 CFR Sec. 21.101 (``Designation of
applicable regulations''), Boeing must show that the Model 707-353B
(USAF C-137) airplanes meet the applicable provisions of the
regulations incorporated by reference in Type Certificate No. 4A26, or
the applicable regulations in effect on the date of application for the
change to the Model 707-353B. 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 707-353B
airplanes includes Civil Air Regulations (CAR) 4b, as amended by
Amendments 4b-1, 4b-2, and 4b-3; and
[[Page 39000]]
additional requirements identified in Type Certificate Data Sheet 4A26.
Purpose of Special Conditions
If the Administrator finds that the applicable airworthiness
regulations do not contain adequate or appropriate safety standards for
an airplane because of a novel or unusual design feature of that
airplane, the FAA may then prescribe special conditions to establish a
level of safety equivalent to that established in the regulations.
Special conditions are authorized under the provisions of 14 CFR 21.16
(``Special conditions'').
Special conditions, as appropriate, are issued in accordance with
14 CFR 11.49, as required by Sec. Sec. 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 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 14 CFR 21.101(a)(1).
Novel or Unusual Design Features
The Boeing STC for the Model 707-353B (USAF C-137) airplanes
includes the upgrade of the INS system from the Litton LTN-72 model to
the LTN-92 model. This INS contains electronic equipment for which the
current airworthiness standards (14 CFR part 25) do not contain
adequate or appropriate safety standards that address protecting this
equipment from the adverse effects of HIRF. Accordingly, this system is
considered to be a ``novel or unusual design feature.''
Discussion
As stated previously, there is no specific regulation that
addresses requirements for protection of electrical and electronic
systems from HIRF external to the airplane. 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, the FAA has
determined that special conditions are needed for the Boeing Model 707-
353B (USAF C-137) modifed to include the upgraded INS. These special
conditions will require that this system, which performs 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.
Protection of Systems from High-Intensity Radiated Fields (HIRF)
Recent advances in technology have given rise to the application in
aircraft designs of advanced electrical and electronic systems that
perform functions required for continued safe flight and landing. Due
to the use of sensitive solid-state advanced components in analog and
digital electronics circuits, these advanced systems are readily
responsive to the transient effects of induced electrical current and
voltage caused by HIRF. Such HIRF can degrade electronic systems
performance by damaging components or by upsetting system functions.
Furthermore, the HIRF environment has undergone a transformation
that was not foreseen when the current requirements were developed:
Higher energy levels are radiated from transmitters that are used for
radar, radio, and television. Also, the number of transmitters has
increased significantly. There also is uncertainty concerning the
effectiveness of airframe shielding for HIRF. Furthermore, coupling to
cockpit-installed equipment through the cockpit window apertures is
undefined.
The combined effect of the technological advances in airplane
design and the changing environment has resulted in an increased level
of vulnerability of electrical and electronic systems required for the
continued safe flight and landing of the airplane. Effective measures
against the effects of exposure to HIRF must be provided during the
design and installation of these systems.
Actions Required by Special Conditions
The accepted maximum energy levels in which airplane system
installations must be capable of operating safely are based on surveys
and analyses of existing radio frequency emitters. These special
conditions require that the airplane be evaluated under these energy
levels for the protection of the electronic system and its associated
wiring harness. These external threat levels, which are lower than
previously required values, are believed to represent the worst case to
which an airplane would be exposed in the operating environment.
These special conditions require that the systems installed in
aircraft that perform critical functions must be qualified to the HIRF
environment defined in paragraph 1., below, or (as an option to a fixed
value using laboratory tests) that defined in paragraph 2, below:
1. The applicant may demonstrate that the operation and operational
capability of the installed electrical and electronic systems that
perform critical functions are not adversely affected when the airplane
is exposed to the HIRF environment defined below:
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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
2 GHz-4 GHz................................... 3000 200
4 GHz-6 GHz................................... 3000 200
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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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The field strengths are expressed in terms of peak root-mean-square
(rms) values.
Or
b. The applicant may demonstrate by a system laboratory test that
the electrical and electronic systems that perform critical functions
withstand an electromagnetic field strength of 100 volts per meter,
without the benefit of airplane structural shielding, over a frequency
range of 10 kHz to 18 GHz.
Note: The field strength values for the HIRF environment and
laboratory test levels are expressed in root-mean-square units
measured during the peak of the modulation cycle, as many laboratory
instruments indicate amplitude. These are commonly called ``peak-
rms'' values. The true peak field strength values will be higher by
a factor of the square root of two.
Applicability
As discussed above, these special conditions are applicable to the
Boeing Model 707-353B (USAF C-137) airplanes modified to include the
upgraded INS. Should Boeing Commercial Airplane Group apply at a later
date for a design change approval to the type certificate to include
any other model incorporating the same novel or unusual design feature,
these special conditions would apply to that model as well, under the
provisions of 14 CFR 21.101(a)(1).
Conclusion
This action affects only certain novel or unusual design features
on the Boeing 707-353B (USAF C-137) airplanes. 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.
Further, the substance of these special conditions 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 in this document. 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. However, 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 supplemental type certification basis for the Boeing Model 707-353B
(USAF C-137) airplanes.
1. Protection of Electrical and Electronic Systems 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 operations and operational capability of
these systems to perform critical functions are not adversely affected
when the airplane is exposed to high-intensity radiated electromagnetic
fields external to the airplane.
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 July 13, 1999.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-18566 Filed 7-20-99; 8:45 am]
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