[Federal Register Volume 62, Number 218 (Wednesday, November 12, 1997)]
[Rules and Regulations]
[Pages 60640-60642]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-29730]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-144; Special Conditions No. 25-ANM-134]
Special Conditions: Learjet Inc. Model 55 Airplane; 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 Learjet Model 55
airplanes modified by Learjet. 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 October 31,
1997. Comments must be received on or before December 29, 1997.
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. NM-144, 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-144. 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 Beane, FAA, Standardization
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056;
telephone (425) 227-2796; facsimile (425) 227-1149.
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 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. 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. NM-144.'' The postcard will
be date stamped and returned to the commenter.
Background
On August 27, 1997, Learjet Inc. applied for a supplemental type
[[Page 60641]]
certificate (STC) to modify Learjet Model 55 airplanes listed on Type
Certificate A10CE. The modification incorporates the installation of a
digital electronic flight instrument system (EFIS) for display of
critical flight parameters (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.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Learjet Inc. must show that
the Learjet Model 55 airplane, as changed, continues to meet the
applicable provisions of the regulations incorporated by reference in
Type Certificate A10CE, 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 Model 55 airplane includes 14 CFR part 25, as amended by
Amendments 25-2 through 25-4, 25-7, 25-10, 25-12, 25-18, 25-21, 25-30,
and certain later amendments, special conditions, exemptions, and
optional requirements listed in the type certificate data sheet that
are not relevant to these special conditions. In addition, the
certification basis for the modifications, and for areas affected by
the modifications, will be amended to include the following sections:
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Section Amendment Title
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25.901.............................. 25-38 Installation.
25.1301(d).......................... 25-38 Function and
Installation.
25.1303............................. 25-38 Flight and navigation
instruments.
25.1309............................. 25-41 Equipment, systems, and
installations.
25.1321............................. 25-41 Arrangement and
visibility.
25.1322............................. 25-38 Warning, caution, and
advisory lights.
25.1331............................. 25-41 Instruments using a
power supply.
25.1333............................. 25-41 Instrument systems.
25.1335............................. 25-41 Flight director
systems.
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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 Learjet Model 55 airplane 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 Learjet Inc. 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, 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 modified Learjet Model 55 will incorporate a new electronic
flight instrument system 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 Learjet Model 55, 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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Peak (V/ Average
Frequency M) (V/M)
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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
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Applicability
As discussed above, these special conditions are applicable to
Learjet Model 55 airplanes modified by Learjet. Should Learjet 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, the 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 Learjet Model
55 airplanes modified by Learjet. 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.
[[Page 60642]]
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.
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 Learjet Model 55 airplanes modified by
Learjet Inc.
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 October 31, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 97-29730 Filed 11-10-97; 8:45 am]
BILLING CODE 4910-13-P
