[Federal Register Volume 61, Number 213 (Friday, November 1, 1996)]
[Rules and Regulations]
[Pages 56408-56409]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28107]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-128; Special Conditions No. 25-ANM-121]


Special Conditions: deHavilland DHC-8-400 Airplane; High-
Intensity Radiated Fields

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued to the de Havilland 
Aircraft Company of Canada for the de Havilland DHC-8-400 airplane. 
This airplane will utilize new avionics/electronic systems that provide 
critical data to the flightcrew. 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. 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.

EFFECTIVE DATE: December 2, 1996.

FOR FURTHER INFORMATION CONTACT:
Tim Backman, FAA, Standardization Branch, ANM-113, Transport Airplane 
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington, 98055-4056, telephone (206) 227-2797 or facsimile 
(206) 227-1149.

SUPPLEMENTARY INFORMATION:

Background

    On January 31, 1995, the de Havilland Aircraft Company of Canada, 
Garratt Boulevard, Downsview, Ontario M3K1Y5, applied for an amendment 
to their Type Certificate No. A13NM to include their new model Dash 8 
Series 400 (DHC-8-400), Model 401/402 airplane, which is a derivative 
of the DHC-8-300. The DHC-8-400 is a high wing, T-tail, twin engine, 
turbopropeller powered regional transport. Each engine will be capable 
of delivering 4830 shaft horsepower. The flight controls are manual, 
except for the tandem rudder which will be hydraulically powered. The 
airplane has a seating capacity of up to 78, and a maximum takeoff 
weight of 62,500 pounds.

Type Certification Basis

    Under the provisions of 14 CFR Sec. 21.101, deHavilland must show 
that the DHC-8-400 meets the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A13NM, or the 
applicable regulations in effect on the date of application for the 
change of the Model 300. 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. A13NM include part 25, as amended by Amendments 
25-1 through 25-51, and certain other later amended sections of part 25 
that are not relevant to these special conditions. In addition, 
deHavilland has chosen to comply with the applicable regulations in 
effect on March 6, 1995; specifically part 25 as amended by Amendments 
25-1 through 25-83. In addition to the applicable airworthiness 
regulations and special conditions, the DHC-8-400 must comply with the 
fuel vent and exhaust emission requirements of part 34, effective 
September 10, 1990, plus any amendments in effect at the time of 
certification; and the noise certification requirements of part 36, 
effective December 1, 1969, as amended by Amendment 36-1 through the 
amendment in effect at the time of certification. No exemptions are 
anticipated. These special conditions will form an additional part of 
the 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 DHC-8-400 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(b), 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 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 Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The DHC-8-400 airplane avionics enhancement will utilize electronic 
systems that perform critical functions,

[[Page 56409]]

including a digital Electronic Flight Instrument System (EFIS), 
attitude and heading reference systems (AHRS), and air data systems 
(ADS). These systems 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.
    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 DHC-8-400, which require that new 
technology electrical and electronic systems, such as the EFIS, AHRS 
and ADS, 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, 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
110 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 are applicable 
initially to the DHC-8-400 airplane. Should de Havilland apply at a 
later date for a change to the type certificate to include another 
model incorporating 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).

Discussion of Comments

    Notice of proposed special conditions No. SC-96-3-NM was published 
in the Federal Register on July 22, 1996 (61 FR 37844). No comments 
were received.

Conclusion

    This action affects certain design features only on the DHC-8-400 
airplane. 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 airplane.

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. 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 deHavilland DHC-8-400 series 
airplanes.
    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 this special condition, 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 October 15, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 96-28107 Filed 10-31-96; 8:45 am]
BILLING CODE 4910-13-M