[Federal Register Volume 66, Number 175 (Monday, September 10, 2001)]
[Rules and Regulations]
[Pages 46937-46939]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-22661]



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  Federal Register / Vol. 66, No. 175 / Monday, September 10, 2001 / 
Rules and Regulations  

[[Page 46937]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM194; Special Conditions No. 25-184-SC]


Special Conditions: Boeing Model 727-200 Airplanes; High-
Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for Boeing Model 727-200 
airplanes modified by Aircraft Systems & Manufacturing. These modified 
airplanes will have a novel or unusual design feature when compared to 
the state of technology envisioned in the airworthiness standards for 
transport category airplanes. The modification incorporates the 
installation of a new electronic air data system, consisting of an 
electronic Horizontal Situation Indicator (HSI) and dual air data 
computers, that performs critical functions. The applicable 
airworthiness 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 September 24, 
2001. Comments must be received on or before October 10, 2001.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Attention: Rules Docket (ANM-113), Docket No. NM194, 1601 
Lind Avenue SW., Renton, Washington 98055-4056; or delivered in 
duplicate to the Transport Airplane Directorate at the above address. 
All comments must be marked: Docket No. NM194. 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: Meghan Gordon, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(425) 227-2138; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice and 
opportunity for prior public comment hereon are impracticable because 
these procedures would significantly delay issuance of the approval 
design and thus delivery of the affected aircraft. In addition, the 
substance of these special conditions has been subject to the public 
comment process in several prior instances with no substantive comments 
received. The FAA therefore finds that good cause exists for making 
these special conditions effective upon issuance.

Comments Invited

    Interested persons are invited to submit such written data, views, 
or arguments as they may desire. Communications should identify the 
rules docket number and be submitted in duplicate to the address 
specified above. The Administrator will consider all communications 
received on or before the closing date for comments. The special 
conditions may be changed in light of the comments received. All 
comments received 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 these special conditions must include with 
those comments a self-addressed, stamped postcard on which the 
following statement is made: ``Comments to Docket No. NM194.'' The 
postcard will be date stamped and returned to the commenter.

Background

    On February 6, 2001, Aircraft Systems & Manufacturing, 302 Toledo 
Trail Drive, Georgetown, Texas, 78628, applied for a Supplemental Type 
Certificate (STC) to modify Boeing Model 727-200 airplanes. These 
airplanes are low-wing, pressurized transport category airplanes with 
three fuselage-mounted jet engines. They are capable of seating between 
170 and 189 passengers, depending upon the model and configuration. The 
modification incorporates the installation of a new electronic air data 
system consisting of an electronic Horizontal Situation Indicator (HSI) 
and dual air data computers. The avionics/electronics and electrical 
systems installed in this airplane have the potential to be vulnerable 
to high-intensity radiated fields (HIRF).

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Aircraft Systems & 
Manufacturing must show that the Boeing Model 727-200 series airplanes, 
as modified to include the new electronic air data system, continue to 
meet the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. A3WE 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 specific 
regulations included in the certification basis for the Boeing Model 
727-200 series airplanes include Civil Air Regulations (CAR) 4b, as 
amended by amendment 4b-1 through 4b-11.
    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 Boeing Model 727-200 series 
airplanes because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Boeing Model 727-200 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 defined in Sec. 11.19, are issued in 
accordance with

[[Page 46938]]

Sec. 11.38, and become part of the airplane's 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 Aircraft Systems & Manufacturing 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 also 
apply to the other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    As noted earlier, the Boeing 727-200 airplanes modified by Aircraft 
Systems & Manufacturing will incorporate a new electronic air data 
system, consisting of an electronic HSI and dual air data computers, 
that will perform critical functions. This system may be vulnerable to 
high-intensity radiated fields. The current airworthiness standards of 
part 25 do not contain adequate or appropriate safety standards for the 
protection of this equipment from the adverse effects of HIRF. 
Accordingly, this system is considered to be a novel or unusual design 
feature.

Discussion

    There is no specific regulation that addresses requirements for 
protection of 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 that is equivalent to 
that intended by the regulations incorporated by reference, special 
conditions are needed for the Boeing Model 727-200 series airplanes 
modified by Aircraft Systems & Manufacturing. These special conditions 
will require that this system, which performs critical functions, must 
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 (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 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 flight deck-
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. Both peak and average 
field strength components from the Table are to be demonstrated.

------------------------------------------------------------------------
                                                 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 to the 
Boeing Model 727-200 series airplanes modified by Aircraft Systems & 
Manufacturing to install a new electronic air data system. Should 
Aircraft Systems & Manufacturing apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. A3WE 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).

Conclusion

    This action affects only certain design features on the Boeing 
Model 727-200 series airplanes modified by Aircraft Systems & 
Manufacturing to include the new electronic air data system. 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 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. 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 supplemental type certification basis for the Boeing Model 727-200 
series airplanes as modified by Aircraft Systems & Manufacturing.
    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

[[Page 46939]]

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 August 24, 2001.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-22661 Filed 9-7-01; 8:45 am]
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