[Federal Register: April 29, 2003 (Volume 68, Number 82)]
[Rules and Regulations]
[Page 22578-22580]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr29ap03-3]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM247, Special Conditions No. 25-232-SC]
Special Conditions: Learjet Model 24/25 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 the Learjet Model 24/
25 series airplanes, as modified by LJSC Ltd. 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. The modification incorporates the installation of
dual IS&S air data display units (ADDU) and a single IS&S analog
interface unit (AIU). 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 provided by the existing
airworthiness standards.
DATES: The effective date of these special conditions is April 14,
2003. Comments must be received on or before May 29, 2003.
ADDRESSES: Comments on these special conditions may be mailed in
duplicate to: Federal Aviation Administration, Transport Airplane
Directorate, Attn: Rules Docket (ANM-113), Docket No.NM247, 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. NM247. 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: Greg Dunn, FAA, Airplane and Flight
Crew Interface Branch, ANM-111, 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 are unnecessary in accordance with 14 CFR 11.38, because the
FAA has provided previous opportunities to comment on substantially
identical special conditions and has fully considered and addressed all
the substantive comments received. Based on a review of the comment
history and the comment resolution, the FAA is satisfied that new
comments are unlikely. The FAA, therefore, finds that good cause exists
for making these special conditions effective upon issuance. However,
the FAA invites interested persons to participate in this rulemaking by
submitting comments, data, or views. The most helpful comments
reference a specific portion of the special conditions, explain the
reason for any recommended change, and include supporting data. We ask
that you send us two copies of written comments.
We will file in the docket all comments we receive, as well as a
report summarizing each substantive public contact with FAA personnel
concerning these special conditions. The docket is available for public
inspection before and after the comment closing date. If you wish to
review the docket in person, go to the address in the ADDRESSES section
of this preamble between 7:30 a.m. and 4 p.m., Monday through Friday,
except Federal holidays.
We will consider all comments we receive on or before the closing
date for comments. We will consider comments filed late if it is
possible to do so without incurring expense or delay. We may change
these special conditions in light of the comments we receive.
If you want the FAA to acknowledge receipt of your comments on this
proposal, include with your comments a pre-addressed, stamped postcard
on which the docket number appears. We will stamp the date on the
postcard and mail it back to you.
Background
On October 8, 2002, LJSC Ltd., 8201 E. 34th North Building 800,
Suite 805, Wichita, Kansas 67226, applied for a supplemental type
certificate (STC) to modify the Learjet Model 24/25 series airplanes
approved under Type Certificate No. A10CE. The modification
incorporates the installation of dual IS&S air data display units
(ADDU), and a single IS&S analog interface unit (AIU).
The dual IS&S air data display units (ADDU) and single IS&S analog
[[Page 22579]]
interface unit (AIU) replace the existing altimetry system. This system
uses electronics to a far greater extent than the original altimetry
system, and may be more susceptible to electrical and magnetic
interference caused by high-intensity radiated fields (HIRF).
Disruption of these signals could result in loss of altitude, or
present misleading information to the pilot.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Amendment 21-69, effective
September 16, 1991, LJSC Ltd. must show that the Learjet Model 24/25
series airplanes, as changed, continue to meet the applicable
provisions of the regulations incorporated by reference in Type
Certificate No. 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 Learjet Model 24/25 series airplanes includes 14 CFR part 25
effective February 1, 1965, as amended by 25-2 and 25-4. Other
applicable amendments, regulations, and special conditions are noted in
Type Certificate Data Sheet (TCDS) A10CE.
If the Administrator finds that the applicable airworthiness
regulations (that is, 14 CFR part 25, as amended) do not contain
adequate or appropriate safety standards for the Learjet Model 24/25
series airplanes because of novel or unusual design features, special
conditions are prescribed under the provisions of Sec. 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the Learjet Model 24/25 series airplanes must comply with
the fuel vent and exhaust emission requirement of 14 CFR part 34 and
the noise certification requirement of part 36.
Special conditions, as defined in 14 CFR 11.19, are issued in
accordance with Sec. 11.38, 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 LJSC Ltd. apply at a later date for a
supplemental type certificate to modify any other model already
included on the same type certificate to incorporate the same novel or
unusual design features, these 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 Learjet Model 24/25 series airplanes will incorporate the
installation of dual IS&S air data display units (ADDU) and a single
IS&S analog interface unit (AIU). Because these advanced systems use
electronics to a far greater extent than the original altimetry system,
they may be more susceptible to electrical and magnetic interference
caused by high-intensity radiated fields (HIRF) external to the
airplane. 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, these instruments are considered to be a novel or unusual
design feature.
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 avionics/electronics and electrical 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 24/25 series airplanes, as
modified to include the new altimetry system. These special conditions
will require that the new dual IS&S air data display units (ADDU) and
single IS&S analog interface unit (AIU), which 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/electronics and electrical
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 (root-mean-square) 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 field strengths
indicated in the table below for the frequency ranges indicated. Both
peak and average field strength components from the table below are to
be demonstrated.
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Field strength
(volts per meter)
Frequency -------------------
Peak Average
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10kHz-100kHz........................................ 50 50
100kHz-500kHz....................................... 50 50
500kHz-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 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
Learjet Model 24/25 series airplanes modified by LJSC Ltd. to include
the dual IS&S air data display units (ADDU) and a single IS&S analog
interface unit (AIU). Should LJSC Ltd. apply at a later date for a
supplemental type certificate to modify any other model already
included on Type Certificate A10CE to incorporate the same novel or
unusual design features, these special conditions would apply to that
model as well under the provisions of 14 CFR 21.101(a)(1).
[[Page 22580]]
Conclusion
This action affects only certain design features on Learjet Model
24/25 series airplanes modified by LJSC Ltd. 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 notice and comment procedure in several prior instances
and has been derived without substantive change from those previously
issued. 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. 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 record keeping
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 Learjet Model 24/25
series airplanes modified by LJSC Ltd.
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 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 April 14, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 03-10450 Filed 4-28-03; 8:45 am]
BILLING CODE 4910-13-P