[Federal Register Volume 59, Number 225 (Wednesday, November 23, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-28917]


[[Page Unknown]]

[Federal Register: November 23, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-102; Special Conditions No. 25-ANM-92]

 

Special Conditions; Modified Cessna Model 501 and 551 Series 
Airplanes, High Intensity Radiated Fields (HIRF)

agency: Federal Aviation Administration, DOT.

action: Final special conditions; request for comments.

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summary: These special conditions are issued for the Cessna 501 and 551 
series airplanes modified by AMR Combs, Inc., of Denver, Colorado. 
These airplanes are equipped with high-technology digital avionic 
systems that perform critical functions. The applicable type 
certification 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 provide the 
additional safety standards that the Administrator considers necessary 
to ensure that the critical functions that these systems perform are 
maintained when the airplane is exposed to HIRF.

dates: The effective date of these special conditions is November 16, 
1994. Comments must be received on or before January 9, 1995.

addresses: Comments on these final special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Office of the Assistant 
Chief Counsel, Attn: Rules Docket (ANM-7), Docket No. NM-102, 1601 Lind 
Avenue SW., Renton, WA 98055-4056; or delivered in duplicate to the 
Office of the Assistant Chief Counsel at the above address. Comments 
must be marked ``Docket No. NM-102.'' Comments may be inspected in the 
Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 
4:00 p.m.

for further information contact: Mark Quam, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, WA 98055-4056; telephone (206) 
227-2145.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that good cause exists for making these 
special conditions effective upon issuance; however, interested persons 
are invited to submit such written data, views, or arguments as they 
may desire. Communications should identify the regulatory docket or 
special conditions 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. These 
special conditions may be changed in light of the comments received. 
All comments submitted will be available in the Rules Docket for 
examination by interested persons, both before and after the closing 
date for comments. A report summarizing such substantive public contact 
with FAA personnel concerning this rulemaking will be filed in the 
docket. Persons wishing the FAA to acknowledge receipt of their 
comments submitted in response to this request must submit with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket No. NM-102.'' The postcard will 
be date stamped and returned to the commenter.

Background

    On September 28, 1994, AMR Combs, Inc., of Denver, Colorado, 
applied for a supplemental type certificate to modify the Cessna Model 
501 and 551 series airplanes. The Model 501 and 551 airplanes are 
single-pilot business jets with two aft-mounted turbojet engines, 
capable of operating with nine and eleven passengers, respectively. The 
proposed modification incorporates the installation of a pilot's side 
Digital Electronic Flight Instrument System (EFIS), which presents 
critical information and annunciation to the pilot. This system is 
potentially vulnerable to high-intensity radiated fields (HIRF) 
external to the airplane.

Supplemental Type Certification Basis

    Under the provisions of Sec. 21.101 of the Federal Aviation 
Regulations (FAR), AMR Combs, Inc., must show that the modified Cessna 
Model 501 and 551 series airplanes continue to meet the applicable 
provisions of the regulations incorporated by reference in Type 
Certificate No. A27CE, 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 Type Certificate No. 
A27CE include the following: 14 CFR part 23 of the FAR, effective 
February 1, 1965, as amended by Amendments 23-1 through 23-16; and 14 
CFR part 25 of the FAR, effective February 1, 1965, as amended by 
Amendments 25-1 through 25-17. Those sections of part 23 and part 25 
that are pertinent to this installation include: Sec. 23.1311, as 
amended through amendment 23-41; Secs. 25.1301, 25.1303(b), and 
25.1322, as amended through Amendment 25-38; and Secs. 25.1309, 
25.1321(a), (b), (d), and (e), 25.1331, 25.1333, and 25.1335, as 
amended through Amendment 25-41. In additon, the certification basis 
may include other amendments and findings of equivalent safety that are 
not relevant to these special conditions. These special conditions will 
form an additional part of the certification basis.
    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 Cessna 501 and 551 series 
airplanes because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec. 21.16 to 
establish a level of safety equivalent to that established in the 
regulations.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR after public notice, as required by Secs. 11.28 
and 11.29, 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 the applicant apply 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, 
the special conditions would also apply to the other model under the 
provisions of Sec. 21.101(a)(1).

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 electrical and electronic 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 modified Cessna 501 and 551 series 
airplanes that would require that new technology electrical and 
electronic systems, such as the EFIS and digital avionics systems, be 
designed and installed to preclude component damage and interruption of 
function due to the 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 systems, such as the EFIS, 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, and adequate level of 
protection exists when compliance with the HIRF protection special 
condition is shown with either paragraphs 1 or 2 below:
    1. A minimum threat of 100 volts per meter peak 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 following field 
strengths for the frequency ranges indicated.

------------------------------------------------------------------------
                                                        Peak (V/ Average
                       Frequency                           M)     (V/M) 
------------------------------------------------------------------------
10 KHz-100 KHz........................................       50       50
100 KHz-500 KHz.......................................       60       60
500 KHz-2000 KHz......................................       70       70
2 MHz-30 MHz..........................................      200      200
30 MHz-70 MHz.........................................       30       30
70 MHz-100 MHz........................................       30       30
100 MHz-200 MHz.......................................      150       33
200 MHz-400 MHz.......................................       70       70
400 MHz-700 MHz.......................................    4,020      935
700 MHz-1000 MHz......................................    1,700      170
1 GHz-2 GHz...........................................    5,000      990
2 GHz-4 GHz...........................................    6,680      840
4 GHz-6 GHz...........................................    6,850      310
6 GHz-8 GHz...........................................    3,600      670
8 GHz-12 GHz..........................................    3,500    1,270
12 GHz-18 GHz.........................................    3,500      360
18 GHz-40 GHz.........................................    2,100      750
------------------------------------------------------------------------

    As discussed above, these special conditions are applicable to the 
Cessna Model 501 and 551 series airplanes, modified by AMR Combs, Inc., 
of Denver, Colorado. Should AMR Combs, Inc. apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. A27CE to incorporate the same novel or unusual 
design feature, the special conditions would apply to that model as 
well, under the provisions of Sec. 21.101(a)(1).

Conclusion

    This action affects only certain unusual or novel design features 
on the Cessna 501 and 551 series airplanes modified by AMR Combs, Inc., 
of Denver, Colorado. 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 Cessna 501 and 551 series airplanes.
    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. 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 immediately. Therefore, these special conditions are being 
made effective 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 recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. app. 1344, 1348(c), 1352, 1354(a), 1355, 
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et 
seq; E.O. 11514; and 49 U.S.C. 106(g).

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 Cessna 501 and 551 series 
airplanes modified by AMR Combs, Inc., of Denver, Colorado.
    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. The following definition applies with respect to these special 
conditions: 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 November 16, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-28917 Filed 11-22-94; 8:45 am]
BILLING CODE 4910-13-M