[Federal Register Volume 63, Number 135 (Wednesday, July 15, 1998)]
[Rules and Regulations]
[Pages 38075-38077]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-18857]
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Rules and Regulations
Federal Register
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Federal Register / Vol. 63, No. 135 / Wednesday, July 15, 1998 /
Rules and Regulations
[[Page 38075]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM147; Special Conditions No. 25-139-SC]
Special Conditions: Boeing Model 757-300; High-Intensity Radiated
Fields
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Boeing Model 757-
300 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: August 14, 1998.
FOR FURTHER INFORMATION CONTACT: John Dimtroff, FAA, Airplane and
Flight Crew Interface Branch, ANM-111, Transport Airplane Directorate,
Aircraft Certification Service, 1601 Lind Avenue SW., Renton,
Washington, 98055-4056, telephone (425) 227-2117 or facsimile (425)
227-1320.
SUPPLEMENTARY INFORMATION:
Background
On February 21, 1996, the Boeing Commercial Airplane Group, P. O.
Box 3707, Seattle, Washington 98124-2207, applied for an amendment to
Type Certificate No. A2NM to include the new Model 757-300, a
derivative of the 757-200. The 757-300 is a swept-wing, conventional-
tail, twin-engine, turbofan-powered transport. Each engine is capable
of delivering 43,100 pounds of thrust. The flight controls are
unchanged beyond those changes deemed necessary to accommodate the
stretched configuration. The airplane has a seating capacity of up to
295, and a maximum takeoff weight of 270,000 pounds (122,470 Kg).
Type Certification Basis
Under the provisions of Title 14 CFR 21.101, Boeing must show that
the Model 757-300 meets the applicable provisions of the regulations
incorporated by reference in Type Certificate No. A2NM, or the
applicable regulations in effect on the date of application for the
change to the Model 757-300. 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. A2NM include 14 CFR part 25, as amended by
Amendments 25-1 through 25-45, and certain other later amended sections
of part 25 that are not relevant to these special conditions. Except
for certain earlier amended sections of part 25 that are not relevant
to these special conditions, Boeing has chosen to comply with part 25
as amended by Amendments 25-1 through 25-85, the applicable regulations
in effect on the date of application. In addition to the applicable
airworthiness regulations and special conditions, the 757-300 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. These special
conditions 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 757-300 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 757-300 airplane avionics enhancement utilizes electronic
systems that perform critical functions, including the following
airframe Line Replaceable Units (LRU): Multi-Mode Receiver (MMR),
Flight Control Computer (FCC), Yaw Damper Stabilizer Trim Module (YSM),
Air Data Inertial Reference System (ADIRS), and the Allied Signal Radio
Altimeter (RA). 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 757-300, which require that new
technology electrical and electronic systems, such as the MMR, FCC,
YSM, ADIRS, and RA, 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
[[Page 38076]]
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.
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Field strength (volts per meter)
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Frequency US UK/European Consolidated
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Peak Avg. Peak Avg. Peak Avg.
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10 kHz-100 kHz.................... 30 30 50 50 50 50
100 kHz-500 kHz................... 40 30 60 60 60 60
500 kHz-2 MHz..................... 30 30 70 70 70 70
2 MHz-30 MHz...................... 190 190 200 200 200 200
30 MHz-70 MHz..................... 20 20 30 30 30 30
70 MHz-100 MHz.................... 20 20 30 30 30 30
100 MHz-200 MHz................... 30 30 150 30 150 30
200 MHz-400 MHz................... 30 30 70 70 70 70
400 MHz-700 MHz................... 80 80 700 40 700 80
700 MHz-1 GHz..................... 690 240 1700 80 1700 240
1 GHz-2 GHz....................... 970 70 5000 360 5000 360
2 GHz-4 GHz....................... 1570 350 4500 360 4500 360
4 GHz-6 GHz....................... 7200 300 5200 300 7200 300
6 GHz-8 GHz....................... 130 80 2000 330 2000 330
8 GHz-12 GHz...................... 2100 80 3500 270 3500 270
12 GHz-18 GHz..................... 500 330 3500 180 3500 330
18 GHz-40 GHz..................... 780 20 NA NA 780 20
The field strengths are expressed in terms of peak root-mean-square (rms) values.
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The threat levels identified above differ from those used in
previous special conditions and 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. In general, these standards are
less critical than the threat level that was previously used as the
basis for earlier special conditions
Discussion of Comments
Notice of Proposed Special Conditions No. 25-98-02-SC for the 757-
300 was published in the Federal Register on March 25, 1998 (63 FR
14381). Three commenters responded.
The first commenter, representing the interests of airline pilots,
concurs with the special conditions as proposed.
The second commenter, the United Kingdom Civil Aviation Authority
(CAA), states that harmonized HIRF requirements and associated guidance
material arising from FAA/Joint Aviation Authorities (JAA)
participation in a working group of the Aviation Rulemaking Advisory
Committee (ARAC) are well established and known to the FAA and should
be applied by the FAA where special conditions of this nature are
required. The commenter also states that the JAA has applied the
harmonized requirements and means of compliance, and as the FAA may be
faced with finding compliance on behalf of the JAA, it may be
inappropriate for the FAA to apply any special condition or means of
compliance that is not in accordance with the harmonized standards.
The FAA concurs with this commenter; however, at the time of
application for certification of the 757-300, the requirements depicted
in the certification program were not fully harmonized. The HIRF
requirements in place at the time were as depicted in the proposed
special condition. Future airplane certification programs will include
the fully harmonized requirements. Also, Boeing can elect to use the
newer, harmonized requirement table if they so choose.
The applicant, Boeing Commercial Airplane Group, also provided
comments on the proposed special conditions. Boeing does not believe a
HIRF special condition should be applied to existing production
airplane models. The FAA does not agree. Section 21.101 of 14 CFR part
21 states that special conditions can be applied to both new and
substantially complete redesigns of a component, equipment
installation, or system installation. Upgrades of existing production
airplanes, if the upgrade incorporates new or substantially complete
redesigns of a component, equipment installation, or system
installation, do fall within the scope of Sec. 21.101.
Boeing also states that applying the HIRF special conditions would
deter them from upgrading existing airplane models. The FAA has
consistently applied the requirements in the HIRF special condition to
avionics upgrades of existing production model airplanes. Many of these
upgrades have been in the form of supplemental type certifications on
Boeing airplanes and were designed and installed by applicants other
than Boeing. The special conditions have not deterred other applicants
from upgrading existing Boeing airplanes. Also, Boeing already applies
the requirements within the HIRF special conditions to existing
production model airplanes. When Boeing certified the Model 777-200 and
the Model 777-300, components, equipment installations, or system
installations from the Model 777-200, which were new or substantially
redesigned, were shown to comply with the requirements of the HIRF
special condition. When the engines on the Model 767 were upgraded to
include Full Authority Digital Engine Controls
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(FADECs), the FADECs were shown to comply with the HIRF special
conditions. The FAA HIRF requirements have been consistent, and Boeing
has been aware of and complied with these requirements for several
years.
Boeing further states that the HIRF special condition would
effectively deter them from upgrading electronic equipment that
incorporates safety and reliability enhancing features. The FAA
requirements in the HIRF special condition reflect the need to address
a known environmental hazard, recognized by the technical and
regulatory community worldwide. Protection against this known
environmental hazard is required by FAA for all systems performing
functions whose failure would contribute to or cause a catastrophic
failure condition that would prevent the continued safe flight and
landing of the airplane. This policy applies, regardless of whether the
new or significantly changed component, equipment, or system is
intended to improve an unrelated safety or reliability issue. Improving
one aspect of safety or reliability should not degrade another aspect
of safety.
The FAA has consistently applied the requirements in the HIRF
special conditions to certification programs for over 12 years,
regardless of whether the certification was based on a new airplane
type, or a change to an existing airplane. Changing this policy for one
model of Boeing airplanes would not be consistent with the FAA policy
over the last 12 years. Therefore, special conditions for the 757-300
are adopted as proposed in Notice 25-98-02-SC.
Applicability
As discussed above, these special conditions are applicable
initially to the Model 757-300 airplane. Should Boeing 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).
Conclusion
This action affects certain design features only on the Model 757-
300. It is not a rule of general applicability and affects only the
manufacturer who applied to the FAA for approval of these features on
this model.
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 Boeing Model 757-300 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 July 7, 1998.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-18857 Filed 7-14-98; 8:45 am]
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