[Federal Register Volume 62, Number 98 (Wednesday, May 21, 1997)]
[Rules and Regulations]
[Pages 27687-27688]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-13264]



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 Rules and Regulations
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  Federal Register / Vol. 62, No. 98 / Wednesday, May 21, 1997 / Rules 
and Regulations  

[[Page 27687]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-142; Special Conditions No. 25-ANM-126]


Special Conditions: McDonnell-Douglas Model DC-9-31/-32, High-
Intensity Radiated Fields

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for McDonnell-Douglas 
Model DC-9-31/-32 airplanes as modified by Innovative Solutions & 
Support, Inc. The Innovative Solutions & Support, Inc. altimeter P/N 
9D-80110-2 will utilize an electronic system which performs a critical 
function. The applicable 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 May 13, 1997. 
Comments must be received on or before July 7, 1997.

ADDRESSES: Comments on these 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-142, 1601 Lind 
Avenue SW., Renton, Washington, 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-142. 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: Joe Jacobsen, Standardization Branch, 
ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(206) 227-2011.

SUPPLEMENTARY INFORMATION:

Comment 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 and 
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. 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 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-142.'' The postcard will 
be date stamped and returned to the commenter.

Background

    On January 17, 1997, Innovative Solutions & Support, Inc. applied 
for a supplemental type certificate to modify the altimeter system of 
McDonnell-Douglas Model DC-9-31/-32 airplanes to an electronic system. 
The Model DC-9-31/-32 is currently approved under Type Certificate No. 
A6WE.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Innovative Solutions & 
Support, Inc. must show that the Model DC-9-31/-32 airplanes meet the 
applicable provisions of the regulations incorporated by reference in 
Type Certificate No. A6WE or the applicable regulations in effect on 
the date of application for the changes to the Model DC-9-31/-32. In 
addition, the certification basis includes certain special conditions 
and later amended sections of 14 CFR part 25 that are not relevant to 
these special conditions.
    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 DC-9-31/-32 because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of 14 CFR 21.16 to establish a level of safety equivalent to 
that established in the regulations.
    In addition to the applicable airworthiness regulations and special 
conditions, the McDonnell Douglas DC-9-31/-32 must comply with the fuel 
and exhaust emission requirements of 14 CFR part 34 and the noise 
certification requirements of 14 CFR part 36.
    Special conditions, as appropriate, are issued in accordance with 
14 CFR 11.49 after public notice, as required by 14 CFR 11.28 and 
11.29, and become part of the type certification basis in accordance 
with 14 CFR 21.101(b)(2).
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design feature, the special conditions would also apply to the 
other model under the provisions of 14 CFR 21.101(a)(1).

Novel or Unusual Design Features

    The Model DC-9-31/-32, as modified, incorporates a new electronic 
altimeter system. This system may be vulnerable to high-intensity 
radiated fields (HIRF) external to the airplane.

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 electrical and electronic systems to command and control 
airplanes have made it necessary to provide adequate protection.

[[Page 27688]]

    To ensure that a level of safety is achieved equivalent to that 
intended by the regulations incorporated by reference, special 
conditions are issued for the DC-9-31/-32, as modified by Innovative 
Solutions & Support, Inc., which require that new technology electronic 
systems, such as altimeter system, 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

    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 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 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-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 would be applicable 
initially to the modified Model DC-9-31/-32. Should Innovative 
Solutions & Support, Inc. apply at a later date for a change to the 
type certificate to include another model incorporating the same novel 
or unusual design feature, these special conditions would apply to that 
model as well, under the provisions of 14 CFR 21.101(a)(1).

Conclusion

    This action affects only certain design features on McDonnell-
Douglas DC-9-31/-32 airplanes. 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 for this airplane 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 proposed special conditions is as 
follows:

    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 the McDonnell-Douglas DC-9-31/-32 
airplane, as modified by Innovative Solutions & Support, 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 Renton, Washington, on May 13, 1997.
Darrell M. Pederson,
 Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 97-13264 Filed 5-20-97; 8:45 am]
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