[Federal Register Volume 68, Number 41 (Monday, March 3, 2003)]
[Rules and Regulations]
[Pages 9854-9856]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-4796]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM240, Special Conditions No. 25-227-SC]


Special Conditions: Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 
24D-A, 24E, 24F, 24F-A, 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: These special conditions are issued for Learjet Model 24, 24A, 
24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D 
and 25F airplanes modified by Royal Air, Inc. These airplanes, as 
modified, 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 the Innovative Solutions & Support (IS&S) Air Data 
Display Units (ADDU) and Air Data Sensor. 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 February 21, 
2003. Comments must be received on or before April 2, 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. NM240, 1601 Lind 
Avenue SW., Renton, Washington 98055-4056; or delivered in duplicate to 
the Transport Airplane Directorate at the above address. Comments must 
be marked: Docket No. NM240. 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 August 17, 2002, Royal Air, Inc., 2141 Airport Road, Waterford, 
Michigan 48327, applied for a supplemental type certificate (STC) to 
modify Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 
24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes approved under Type 
Certificate No. A10CE. The Learjet Model 24/25 series airplanes are 
small transport category airplanes powered by two turbojet engines, 
with maximum takeoff weights of up to 15,000 pounds. These airplanes 
operate with a 2-pilot crew and can seat 6 to 8 passengers. The 
modification incorporates the installation of the Innovative Solutions 
& Support (IS&S) Air Data Display Units (ADDU) and Air Data Sensor. The 
ADDU digital air data computing altimeter provides flight critical 
functions. These advanced systems have the potential to be vulnerable 
to high-intensity radiated fields (HIRF) external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Amendment 21-69, effective 
September 16, 1991, Royal Air must show that the Learjet Model 24, 24A, 
24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 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. Subsequent changes have been made 
to Sec.  21.101 as part of Amendment 21-77, but those changes do not 
become effective until June 10, 2003. 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 Model 24, 24A, 24B, 24B-A, 24C, 24D, 
24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes 
includes 14 CFR part 25, dated February 1, 1965, through Amendments 25-
2 and 25-4; and 14 CFR part 25, dated February 1, 1965, through 
Amendment 25-18, except for special conditions and exceptions noted in 
Type Certificate Data Sheet (TCDS) A10CE.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25, as amended) do not contain adequate 
or appropriate safety standards for the Learjet Model 24, 24A, 24B, 
24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and

[[Page 9855]]

25F 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, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 
24E, 24F, 24F-A, 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 requirement of part 36, including Amendment 
36-1.
    Special conditions, as defined in Sec.  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 Royal Air 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 or similar 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

    As noted earlier, the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 
24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes will 
incorporate new Air Data Display Units (ADDU) and Air Data Sensor that 
will perform critical functions. These systems have the potential to be 
vulnerable to 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 for the protection of 
this equipment from the adverse effects 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 equivalent to that 
intended by the regulations incorporated by reference, special 
conditions are needed for the Learjet Model 24, 24A, 24B, 24B-A, 24C, 
24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes 
modified by Royal Air, Inc. 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, 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 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 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-500kHz....................................         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 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, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 
25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. 
Should Royal Air 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 or similar 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 Learjet Model 
24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 
25C, 25D and 25F airplanes modified by Royal Air. 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 these airplanes 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.

    The authority citation for these special conditions is as follows:


[[Page 9856]]


    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 24, 24A, 24B, 24B-A, 
24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F 
airplanes modified by Royal Air, 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 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 February 21, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-4796 Filed 2-28-03; 8:45 am]
BILLING CODE 4910-13-P