[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
