[Federal Register Volume 71, Number 234 (Wednesday, December 6, 2006)]
[Rules and Regulations]
[Pages 70646-70648]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-20276]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM360; Special Conditions No. 25-337-SC]


Special Conditions: Learjet 25, 25A, 25B, 25C, 25D, and 25F 
Airplanes; High-Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: The FAA issues these special conditions for Learjet 25, 25A, 
25B, 25C, 25D, and 25F airplanes modified by Envoy Aerospace, LLC. 
These modified airplanes will have novel or unusual design features 
when compared with the state of technology envisioned in the 
airworthiness standards for transport category airplanes. The 
modification consists of installing Universal Avionics EFI-890 
Electronic Flight Displays and Rockwell Collins AHS-1000A Attitude 
Heading Reference Systems. The applicable airworthiness regulations do 
not contain adequate or appropriate safety standards for protecting 
these systems from 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 established by the existing airworthiness standards.

DATES: The effective date for these special conditions is November 13, 
2006. We must receive your comments on or before January 5, 2007.

ADDRESSES: You may mail or deliver comments on these special conditions 
in duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Attention: Rules Docket (ANM-113), Docket No. NM360, 1601 
Lind Avenue, SW., Renton, Washington 98057-3356. You must mark your 
comments Docket No. NM360.

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 98057-3356; telephone (425) 227-2799; facsimile (425) 227-
1320.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that notice and opportunity for prior public 
comment for these special conditions is impracticable, because these 
procedures would significantly delay certification and 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. We therefore 
find that good cause exists for making these special conditions 
effective upon issuance. However, we invite interested persons to take 
part in this rulemaking by submitting written comments. The most 
helpful comments reference a specific portion of the special 
conditions,

[[Page 70647]]

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 
about these special conditions. You may inspect the docket 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 based on the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, 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 June 3, 2006, Envoy Aerospace, LLC of Naperville, Illinois, 
applied to the FAA Chicago Aircraft Certification Office for a 
supplemental type certificate to modify Learjet Model 25, 25A, 25B, 
25C, 25D, and 25F airplanes approved under Type Certificate No. A10CE. 
These are transport category airplanes powered by two turbofan engines 
with maximum takeoff weights of up to 15,000 pounds. The airplanes 
operate with a 2-pilot crew and can seat up to 8 passengers. The 
proposed modification incorporates the installation of Universal 
Avionics EFI-890 Electronic Flight Displays and Rockwell Collins AHS-
1000A Attitude Heading Reference Systems. These systems have a 
potential to be vulnerable to high-intensity radiated fields (HIRF) 
external to the airplane.

Type Certification Basis

    Under provisions of 14 CFR 21.101, Envoy Aerospace, LLC must show 
that the Learjet 25, 25A, 25B, 25C, 25D, and 25F 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 original type certification basis for the 
modified Learjet 25, 25A, 25B, 25C, 25D, and 25F airplanes includes 14 
CFR Part 25, as amended by 25-2 and 25-4, and FAA Special Conditions as 
set forth in a letter to Learjet dated March 1, 1967. For further 
details refer to Type Certificate No. A10CE.
    If the Administrator finds that the applicable airworthiness 
regulations (part 25, as amended) do not contain adequate or 
appropriate safety standards for the Learjet 25, 25A, 25B, 25C, 25D, 
and 25F airplanes because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Learjet 25, 25A, 25B, 25C, 25D, and 25F airplanes must 
comply with the fuel vent and exhaust emission requirements of 14 CFR 
part 34 and the noise certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in Sec.  11.19, under 
Sec.  11.38, and they become part of the type certification basis under 
the provisions of Sec.  21.101.

Novel or Unusual Design Features

    As noted earlier, the Learjet 25, 25A, 25B, 25C, 25D, and 25F 
airplanes modified by Envoy Aerospace, LLC will incorporate digital 
flight display and attitude reference systems that will perform 
critical functions. These systems may be vulnerable to high-intensity 
radiated fields external to the airplane. Current airworthiness 
standards of part 25 do not contain adequate or appropriate safety 
standards for protecting this equipment from adverse effects of HIRF. 
So these system are considered to be novel or unusual design features.

Discussion

    As previously stated, there is no specific regulation that 
addresses protection for electrical and electronic systems from HIRF. 
Increased power levels from radio frequency 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 25, 25A, 25B, 25C, 25D, and 25F 
airplanes modified by Envoy Aerospace, LLC. These special conditions 
require that new avionics/electronics and electrical systems that 
perform critical functions be designed and installed to preclude 
component damage and interruption of function because of HIRF.

High-Intensity Radiated Fields (HIRF)

    High-power radio frequency transmitters for radio, radar, 
television, and satellite communications can adversely affect operation 
of airplane electric and electronic systems. Therefore, the immunity of 
critical avionics/electronics and electrical systems to HIRF must be 
established.
    Based on surveys and an analysis of existing HIRF emitters, an 
adequate level of protection exists when airplane system immunity is 
demonstrated when exposed to the HIRF environments in either paragraph 
1 or 2 below:
    1. A minimum environment of 100 volts rms (root-mean-square) per 
meter electric field strength from 10 KHz to 18 GHz.
    a. System elements and their associated wiring harnesses must be 
exposed to the environment without benefit of airframe shielding.
    b. Demonstration of this level of protection is established through 
system tests and analysis.
    2. An environment external to the airframe of the field strengths 
shown in the table below for the frequency ranges indicated. Immunity 
to both peak and average field strength components from the table must 
be demonstrated.

------------------------------------------------------------------------
                                                        Field strength
                                                       (volts per meter)
                      Frequency                      -------------------
                                                        Peak     Average
------------------------------------------------------------------------
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
------------------------------------------------------------------------
The field strengths are expressed in terms of peak of the root-mean-
  square (rms) over the complete modulation period.

    The environment levels identified above are the result of an FAA 
review of existing studies on the subject of HIRF and of the work of 
the Electromagnetic Effects Harmonization Working Group of the Aviation 
Rulemaking Advisory Committee.

[[Page 70648]]

Applicability

    These special conditions are applicable to Learjet 25, 25A, 25B, 
25C, 25D, and 25F airplanes modified by Envoy Aerospace, LLC. Should 
Envoy Aerospace, LLC apply at a later date for a supplemental type 
certificate to modify any other model included on Type Certificate No. 
A10CE to incorporate the same or similar novel or unusual design 
feature, these special conditions would apply to that model as well 
under provisions of Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on Learjet 25, 25A, 25B, 25C, 25D, and 25F airplanes modified by Envoy 
Aerospace, LLC. It is not a rule of general applicability and affects 
only the applicant which applied to the FAA for approval of these 
design features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.


0
The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

0
Therefore, under the authority delegated to me by the Administrator, 
the following special conditions are issued as part of the supplemental 
type certification basis for the Learjet 25, 25A, 25B, 25C, 25D, and 
25F airplanes modified by Envoy Aerospace, LLC.
    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 these special conditions, the following 
definition applies:
    Critical Functions: Functions whose failure would contribute to or 
cause a failure condition that would prevent continued safe flight and 
landing of the airplane.

    Issued in Renton, Washington, on November 13, 2006.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-20276 Filed 12-5-06; 8:45 am]
BILLING CODE 4910-13-P