[Federal Register Volume 63, Number 120 (Tuesday, June 23, 1998)]
[Rules and Regulations]
[Pages 34121-34123]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-16632]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM149, Special Conditions No. 25-138-SC]
Special Conditions: McDonnell Douglas DC-9-81,-82 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 McDonnell Douglas DC-
9-81, -82 airplanes modified by Midwest Express Airlines. 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 special conditions contain the
additional safety standards that the Administrator considers necessary
to establish a level of safety equivalent to that provided by the
existing airworthiness standards.
DATES: The effective date of these special conditions is June 11, 1998.
Comments must be received on or before August 7, 1998.
ADDRESSES: Comments on these special conditions may be mailed in
duplicate to: Federal Aviation Administration, Office of the Assistant
Chief Counsel, Attn: Rules Docket (ANM-7), Docket No. NM149, 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. NM149. 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: Connie Beeane, 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) 227-2796.
SUPPLEMENTARY INFORMATION:
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 docket and special
conditions 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 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. NM149.'' The postcard will
be date stamped and returned to the commenter.
Background
On March 12, 1998, Midwest Express Airlines applied for a
supplemental type certificate (STC) to modify McDonnell Douglas DC-9-
81, -82 airplanes listed on Type Certificate A6WE. The modification
incorporates the installation of electronic flight instrument system
(EFIS) for display of critical flight parameters (altitude, airspeed,
and attitude) to the crew. These displays can be susceptible to
disruption to both command/response signals as a result of electrical
and magnetic interference. This disruption of signals could result in
loss of all critical flight displays and annunciations or present
misleading information to the pilot.
[[Page 34122]]
Type Certification Basis
Under the provisions of 14 CFR Sec. 21.101, Midwest Express
Avionics must show that the McDonnell Douglas DC-9-81, -82 airplanes,
as changed, continue to meet the applicable provisions of the
regulations incorporated by reference in Type Certificate No. A6WE, 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 certification basis for the modified
McDonnell Douglas DC-9-81, -82 airplanes include 14 CFR part 25, dated
February 1, 1965, with Amendments 1 through 40, as amended by TCDS
A6WE.
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 McDonnell Douglas DC-9-81, -82
airplanes because of novel or unusual design features, 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
14 CFR 11.49 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 Midwest Express Airlines apply at a later date
for design change approval to modify any other model already 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
The modified McDonnell Douglas DC-9-81, -82 will incorporate a new
electronic flight instrument system (EFIS), which was not available at
the time of certification of these airplanes, that performs critical
functions. This system 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, special
conditions are needed for the McDonnell Douglas DC-9-81, -82, which
require that new electrical and electronic systems, such as the EFIS,
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 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.
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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
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.
The threat levels identified above differ from those used in
previous special conditions 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 are applicable to
McDonnell Douglas DC-9-81, -82 airplanes modified by Midwest Express
Airlines. Should Midwest Express Airlines apply at a later date for
design change approval to modify any other model included on the same
type certificate 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 McDonnell
Douglas DC-9-81, -82 airplanes modified by Midwest Express Avionics. 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 conditions 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 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
[[Page 34123]]
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 type certification basis for McDonnell Douglas DC-9-81, -82
airplanes modified by Midwest Express Airlines.
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. 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 June 11, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-16632 Filed 6-22-98; 8:45 am]
BILLING CODE 4910-13-P
