[Federal Register Volume 69, Number 135 (Thursday, July 15, 2004)]
[Rules and Regulations]
[Pages 42329-42331]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-16101]



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  Federal Register / Vol. 69, No. 135 / Thursday, July 15, 2004 / Rules 
and Regulations  

[[Page 42329]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM286; Special Conditions No. 25-270-SC]


Special Conditions: Learjet Inc., Model 55, 55B and 55C 
Airplanes; High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for Learjet Inc., Model 
55, 55B and 55C airplanes modified by Garrett Aviation Services. These 
modified airplanes will have a novel or unusual design feature when 
compared to the state of technology envisioned in the airworthiness 
standards for transport category airplanes. The modification 
incorporates the installation of two Honeywell N1 Digital Electronic 
Engine Controls (DEEC) that perform critical functions. 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 established by the 
existing airworthiness standards.

DATES: The effective date of these special conditions is July 1, 2004. 
Comments must be received on or before August 16, 2004.

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. NM286, 1601 Lind 
Avenue, SW., Renton Washington, 98055-4056; or delivered in duplicate 
to the Transport Directorate at the above address. All comments must be 
marked: Docket No. NM286.

FOR FURTHER INFORMATION CONTACT: Meghan Gordon, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
telephone (425) 227-2138; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that notice and opportunity for prior public 
comment is impracticable because these procedures would significantly 
delay certification of and delivery of the affected airplanes. 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. 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 thru 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 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 December 1, 2003, Garrett Aviation Services, 1200 North Airport 
Drive, Capital Airport Springfield, IL 62707, applied for a 
Supplemental Type Certificate (STC) to modify Learjet Inc., Model 55, 
55B and 55C airplanes approved under Type Certificate No. A10CE. The 
Learjet Inc., Model 55, 55B and 55C airplanes are transport category 
airplanes. The Learjet Inc., Model 55, 55B and 55C airplanes are 
powered by two Garrett TFE731-3A-2B turbofans with a maximum takeoff 
weight of 21,500 pounds. These aircraft operate with a 2-pilot crew and 
can hold up to 10 passengers. The modification incorporates the 
installation of Honeywell N1 Digital Electronic Engine Controls (DEEC). 
The N1 DEEC is a replacement for the existing Analog Electronic Engine 
Control (EEC), while also providing additional functional capability in 
the system. The digital avionics/electronics and electrical systems 
installed under this project in these airplanes have the potential to 
be vulnerable to HIRF external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Garrett Aviation Services 
must show that the Learjet Inc., Model 55, 55B and 55C 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 Inc., Model 55, 
55B and 55C airplanes include 14 CFR part 25, dated February 1, 1964, 
as amended by Amendments 25-1 through 25-20 except for special 
conditions and exceptions noted in Type Certificate Data Sheet (TDCS) 
A10CE.
    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 Inc., Model 55, 55B and 
55C airplanes because of novel or unusual design features, special

[[Page 42330]]

conditions are prescribed under the provisions Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Learjet Inc., Model 55, 55B and 55C airplanes must 
comply with 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.
    Special conditions are initially applicable to the model for which 
they are issued. Should Garrett Aviation Services apply at a later date 
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, these special conditions would also apply to the other 
model under the provisions of Sec.  21.101.

Novel or Unusual Design Features

    The Learjet Inc., Model 55, 55B and 55C airplanes modified by 
Garrett Aviation Services will incorporate Honeywell N1 DEEC that will 
perform critical functions. These systems have to potential to be 
vulnerable to HIRF external to the airplane. The current airworthiness 
standards (14 CFR part 25) do not contain adequate or appropriate 
safety standards for the protection of this equipment from the adverse 
effect of HIRF. Accordingly, this system is 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 that is equivalent to 
that intended by the regulations incorporated by reference; special 
conditions are needed for Learjet Inc., Models 55, 55B and 55C 
airplanes modified by Garrett Aviation Services. 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 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, and the advent of space and satellite communications, 
coupled with electronic command and control of the airplane, the 
immunity of critical 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 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 
identified in the following table for the frequency ranges indicated. 
Both peak and average field strength components from the Table are to 
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-30MHz.......................................        100        100
30 MHz-70 MHz.....................................         50         50
70 MHz-100MHz.....................................         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-4GHz........................................       3000        200
4 GHz-6 GHz.......................................       3000        200
6 GHz-8 GHz.......................................       1000        200
8GHz-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 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 Inc., Model 55, 55B and 55C airplanes modified by Garret 
Aviation Services. Should Garrett Aviation Services apply at a later 
date 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, these special conditions would apply to that 
model as well under the provisions of Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on the Learjet Inc., Model 55, 55B and 55C airplanes modified by 
Garrett Aviation Services. 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 these special conditions has been subjected to the 
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.


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
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 the Learjet Inc., Model 
55, 55B and 55C airplanes modified by Garrett Aviation Services.
    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

[[Page 42331]]

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 the 
continued safe flight and landing of the airplane.

    Issued in Renton, Washington, on July 1, 2004.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-16101 Filed 7-14-04; 8:45 am]
BILLING CODE 4910-13-P