[Federal Register Volume 65, Number 59 (Monday, March 27, 2000)]
[Rules and Regulations]
[Pages 16128-16129]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-7495]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM165, Special Conditions No. 25-158-SC]


Special Conditions: McDonnell Douglas DC-9-30 Series Airplanes; 
High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for McDonnell Douglas DC-
9-30 series airplanes modified by Lockheed Martin Aircraft Center. 
These airplanes will have novel and unusual design features when 
compared to the state of technology envisioned in the airworthiness 
standards for transport category airplanes. These airplanes will 
utilize electronic 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 establish a level of safety 
equivalent to that provided by the existing airworthiness standards.

EFFECTIVE DATE: March 13, 2000.

FOR FURTHER INFORMATION CONTACT: Connie Beane, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; 
telephone (425) 227-2796; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Background

    On April 20, 1998, Lockheed Martin Aircraft Center, Inc. (LMAC), 
244 Terminal Road, Greenville, NC 29605, applied for a supplemental 
type certificate (STC) to modify McDonnell Douglas DC-9-30 series 
airplanes listed on Type Certificate A6WE. The modification 
incorporates the installation of a Rockwell-Collins FDS-255 Electronic 
Flight Instrument System, consisting of an electronic attitude display, 
an electronic horizontal situation indicator, and a display controller 
for each pilot. This advanced system uses electronics to a far greater 
extent than the original mechanical attitude displays and may be more 
susceptible to electrical and magnetic interference. This disruption of 
signals could result in loss of attitude display or present misleading 
attitude information to the pilot.
    In addition, on August 18, 1998, LMAC applied for an additional STC 
to modify McDonnell Douglas DC-9-30 series airplanes listed on Type 
Certificate A6WE. The modification incorporates the installation of an 
Innovative Solution & Support electronic air data instrument system, 
which consists of an electronic airspeed display, an electronic 
altimeter, and a digital air data computer for each pilot. This 
advanced system uses electronics to a far greater extent than the 
original pneumatic pitot-static instruments and may be more susceptible 
to electrical and magnetic interference. This disruption of signals 
could result in loss of air data display or present misleading air data 
information to the pilot.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, LMAC must show that the 
McDonnell Douglas DC-9-30 series airplanes, as changed, continue to 
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 change. The regulations 
incorporated by reference in the type certificate are commonly referred 
to as the ``original type certification basis.'' The certification 
basis for the modified McDonnell Douglas DC-9-30 series airplanes 
includes CAR 4b, dated December 31, 1953, with Amendments 4b-1 through 
4b-16, as amended by Type Certificate Data Sheet (TCDS) A6WE.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., CAR 4b, as amended) do not contain adequate or 
appropriate safety standards for the McDonnell Douglas DC-9-30 series 
airplanes because of novel or unusual design features, special 
conditions are prescribed under the provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model DC-9-30 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, are issued in accordance with 
14 CFR 11.49, 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 LMAC apply at a later date for design change 
approval to modify any other model already

[[Page 16129]]

included on the same type certificate to incorporate the same novel or 
unusual design feature, these special conditions would also apply to 
the other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The modified McDonnell Douglas DC-9-30 series airplanes will 
incorporate an electronic attitude display system and an electronic air 
data system, which were not available at the time of certification of 
these airplanes, both of which perform critical functions. These 
systems may be vulnerable to 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 McDonnell Douglas DC-9-30 series 
airplanes. These special conditions require that new electrical and 
electronic systems, such as the electronic attitude and air data 
display 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

    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 paragraph 1, OR 2 below:
    1. A minimum threat of 100 volts rms 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 following field 
strengths for the frequency ranges indicated.

------------------------------------------------------------------------
                                                  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 
initially to the McDonnell Douglas DC-9-30 series airplanes modified by 
LMAC. Should LMAC apply at a later date 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, 
these 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. 25-99-09-SC was published 
in the Federal Register on December 3, 1999 (64 FR 67804). One 
commenter responded, expressing support for the special conditions. The 
special conditions are therefore adopted as proposed.

Conclusion

    This action affects only certain novel or unusual design features 
on the McDonnell Douglas DC-9-30 series airplanes modified by LMAC. It 
is not a rule of general applicability and it affects only the 
applicant 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 McDonnell Douglas DC-9-30 series 
airplanes modified by Lockheed Martin Aircraft Center.
    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 March 13, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 00-7495 Filed 3-24-00; 8:45 am]
BILLING CODE 4910-13-P