[Federal Register Volume 60, Number 2 (Wednesday, January 4, 1995)]
[Rules and Regulations]
[Pages 325-327]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-74]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-104; Special Conditions No. 25-ANM-93]


Special Conditions: Modified Cessna 550 Series Airplanes, High 
Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions with request for comments.

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SUMMARY: These special conditions are issued for the Cessna 550 series 
airplanes modified by Modern Avionics, Inc., of Eden Praire, Minnesota. 
These airplanes are equipped with digital electronic flight instrument 
systems (EFIS) 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 December 20, 
1994. Comments must be received on or before February 21, 1995.

ADDRESSES: Comments on these special conditions may be mailed in 
triplicate to: Federal Aviation Administration, Transport Airplane 
Directorate (ANM-100), Attn: Docket No. NM-104, 1601 Lind Avenue SW, 
Renton, WA 98055-4056; or delivered in triplicate to the Transport 
Airplane Directorate at the above address. Comments must be marked; 
Docket No. NM-104. Comments may be inspected weekdays, except Federal 
holidays, between 7:30 a.m. and 4:00 p.m.

FOR FURTHER INFORMATION CONTACT: Michael Zielinski, FAA, 
Standardization Branch, ANM-113, Transport Airplane Directorate, 
Aircraft [[Page 326]] Certification Service, 1601 Lind Avenue SW, 
Renton, WA 98055-4056; telephone (206) 227-2279.

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 triplicate 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 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. 
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-104.'' The postcard will be date 
stamped, and returned to the commenter.

Background

    On November 9, 1994, Modern Avionics, Inc., of Eden Praire, 
Minnesota, applied for a supplemental type certificate to modify the 
Cessna 550 series airplanes. The Cessna 550 is a business jet with two 
aft-mounted turbofan engines. The airplane can carry two pilots and up 
to 11 passengers, depending on the exit and interior configuration, and 
is capable of operating to 43,000 feet altitude. The proposed 
modification incorporates the installation of digital avionics 
consisting of an electronic flight instrument system (EFIS) that is 
potentially vulnerable to HIRF external to the airplane.

Supplemental Type Certification Basis

    Under the provisions of Sec. 21.101 of the FAR, Modern Avionics, 
Inc., must show that the modified Cessna 550 series airplanes continue 
to meet the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. A22CE, 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 Certification No. 
A22CE include the following: Part 25 of the Federal Aviation 
Regulations (FAR), dated February 1, 1965, including Amendments 25-1 
through 25-17. In addition the following sections of the FAR apply to 
the EFIS installation: Secs. 25.1303(b) and 25.1322, as amended through 
Amendment 25-38; Secs. 25.1309, 25.1321 (a), (b), (d), and (e), 
25.1331, 25.1333, and 25.1335, as amended by Amendment 25-41. These 
special conditions will form an additional part of the supplemental 
type 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 550 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).

Discussion

    There is no special 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 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 Cessna 550 series airplanes that would 
require that new technology electrical and electronic systems, such as 
EFIS and digital avionics systems be designed and installed to preclude 
component damage and interruption of function due to both the direct 
and indirect effects of HIRF.
    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).

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, 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 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.

------------------------------------------------------------------------
                                                                Average 
                     Frequency                      Peak(V/M)    (V/M)  
------------------------------------------------------------------------
10 KHz-100 KHz....................................         50         50
100 KHz-500 KHz...................................         60         60
500 KHz-2 MHz.....................................         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-1 GHz.....................................      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
------------------------------------------------------------------------

    The envelope given in paragraph 2 above is a revision to the 
envelope used in previously issued special conditions in other 
certification projects. It is based on new data and SAE AE4R 
subcommittee recommendations. This revised envelope includes data from 
Western Europe and the U.S. It will also be adopted by the European 
Joint Aviation Authorities.
    As discussed above, these special conditions are applicable to the 
Cessna 550 series airplanes, modified by [[Page 327]] Modern Avoinics, 
Inc., of Eden Praire, Minnesota. Should Modern Avionics, Inc., apply at 
a later date for a supplemental type certificate to modify any other 
model included on Type Certificate No. A22CE 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 550 series airplanes modified by Modern Avionics, Inc., 
of Eden Praire, Minnesota. It is not a rule of general applicability 
and affects only the manufacturer who applied to the FAA for approval 
of these features on the Cessna 550 series airplanes modified by Modern 
Avionics, Inc., of Eden Praire, Minnesota.
    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 have not been submitted in 
response to the prior opportunities for comment described above.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Federal Aviation Administration, 
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. 1875f-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 550 series 
airplanes modified by Modern Avionics, Inc., of Eden Praire, Minnesota.
    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 definitions apply 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 December 20, 1994.
Darrell M. Pederson,
Assistant Manager, Transport Airplane Directorate, Aircraft 
Certification Service.
[FR Doc. 95-74 Filed 1-3-95; 8:45 am]
BILLING CODE 4910-13-M