[Federal Register Volume 71, Number 164 (Thursday, August 24, 2006)]
[Rules and Regulations]
[Pages 49987-49989]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-13995]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE258; Special Conditions No. 23-198-SC]


Special Conditions: Avcon Industries, Inc.; Learjet Model 23 
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 to Avcon Industries, Inc., 
for the Learjet Model 23 series airplanes modified by Avcon Industries, 
Inc. This airplane as modified by Avcon Industries, Inc., will have a 
novel or unusual design feature associated with the installation of a 
new Reduced Vertical Separation Minimum (RVSM) air data system. 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 August 17, 
2006. Comments must be received on or before September 25, 2006.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Regional Counsel, ACE-7, 
Attention: Rules Docket CE258, 901 Locust, Room 506, Kansas City, 
Missouri 64106 or delivered in duplicate to the Regional Counsel at the 
above address. Comments must be marked: CE258. 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: Ervin Dvorak, Federal Aviation 
Administration, Aircraft Certification Service, Small Airplane 
Directorate, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 
64106; 816-329-4123; fax 816-329-4090.

SUPPLEMENTARY INFORMATION:
    The FAA has determined that notice and opportunity for prior public 
comment hereon are impracticable because these procedures would 
significantly delay issuance of the approval design and thus 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. The FAA 
therefore finds that good cause exists for making these special 
conditions effective on issuance.

Comments Invited

    Interested persons are invited to submit such written data, views, 
or arguments as they may desire. Communications should identify the 
regulatory docket or 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. The special conditions may be changed in light of the 
comments received. All comments received 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. Commenters wishing the FAA to acknowledge receipt of their 
comments submitted in response to this notice must include a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to CE258.'' The postcard will be date stamped and returned 
to the commenter.

Background

    On June 26, 2006, Avcon Industries, Inc.; P.O. Box 748; Newton, 
Kansas 67114, applied for a supplemental type certificate (STC) to 
modify Learjet Model 23 series airplanes currently approved under Type 
Certificate (TC) No. A5CE. The Learjet 23 series airplanes are normal 
category airplanes powered by two turbojet engines, with a maximum 
takeoff weight of 12,500 pounds. These airplanes operate with a 2-
person crew and can seat up to 8 passengers. The proposed modification 
is the installation of an Innovative Solutions & Support Air Data 
Display Units and Analog Interface Unit. The avionics/electronics and 
electrical systems installed in this airplane have the potential to be 
vulnerable to HIRF external to the airplane.

Type Certification Basis

    Under the provisions of Sec.  21.101, Avcon Industries, Inc., must 
show that the Learjet Model 23 series airplanes, as changed, continue 
to meet the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. A5CE, 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 regulations 
incorporated by reference in the Type Certificate No. A5CE for the 
Learjet Model 23 series airplanes includes Civil Air Regulations (CAR), 
part 3, effective May 15, 1956, as amended by Amendments 3-1 through 3-
8, plus special conditions set forth in FAA letter to Learjet, dated 
November 12, 1963, and Amendment No. 1, dated July 31, 1964, and No. 2, 
dated March 14, 1966, and Exception No. 352 from compliance with CAR 
3.74(a)(2) and (3) for ground operation at a maximum weight of 12,750 
pounds.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 23, as amended) do not

[[Page 49988]]

contain adequate or appropriate safety standards for the Learjet Model 
23 series 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 Model 23 series 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.
    Special conditions, as appropriate, 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.
    Special conditions are initially applicable to the model for which 
they are issued. Should Avcon Industries, Inc., apply for a 
supplemental type certificate to modify any other model included on TC 
No. A5CE to incorporate the same or a similar 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 Model 23 series airplanes, as modified by Avcon 
Industries, Inc., will incorporate an Innovative Solutions & Support 
Air Data Display Units and Analog Interface Unit. The Innovative 
Solutions & Support Air Data Display Units and Analog Interface Unit 
perform critical functions. These systems may be vulnerable to HIRF 
external to the airplane. The current airworthiness standards of part 
23 do not contain adequate or appropriate safety standards for the 
protection of this equipment from the adverse effects of HIRF. 
Therefore, we consider this system 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 23 series airplanes as 
modified by Avcon Industries, 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, 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 table below 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-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 23 series airplanes modified by Avcon Industries, Inc. 
Should Avcon Industries, Inc., apply later for an STC to modify any 
other model included on TC No. A5CE 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 23 series airplanes modified by Avcon Industries, Inc. 
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. It is 
unlikely that prior public comment would result in a significant change 
from the substance contained herein. 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 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 23

    Aircraft, Aviation safety, Signs and symbols.

Citation

    The authority citation for these special conditions is as follows:


[[Page 49989]]


    Authority: 49 U.S.C. 106(g); 40113, and 44701; 14 CFR 21.16 and 
21.101; and 14 CFR 11.38 and 11.19.

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 the Learjet Model 23 series airplanes 
modified by Avcon Industries, 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.
    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 Kansas City, Missouri on August 17, 2006.
David R. Showers,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-13995 Filed 8-23-06; 8:45 am]
BILLING CODE 4910-13-P