[Federal Register Volume 61, Number 226 (Thursday, November 21, 1996)]
[Proposed Rules]
[Pages 59202-59203]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-29822]


 ========================================================================
 Proposed Rules
                                                 Federal Register
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
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 

  Federal Register / Vol. 61, No. 226 / Thursday, November 21, 1996 / 
Proposed Rules  

[[Page 59202]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-135, Notice No. SC-96-8-NM]


Special Conditions: Boeing Model 767-27C, Airborne Warning and 
Control System Modification (AWACS) Airplanes; Liquid Oxygen

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for Boeing Model 767-
27C airplanes, modified by installation of an Airborne Warning and 
Control System (AWACS). These airplanes will be equipped with an oxygen 
system utilizing liquid oxygen for storage to allow extended, 
unpressurized operations. The applicable regulations do not contain 
adequate or appropriate safety standards for the design and 
installation of oxygen systems utilizing liquid oxygen for storage. 
This notice contains the additional safety standards that the 
Administrator considers necessary to ensure that the design and 
installation of the oxygen system utilizing liquid oxygen for storage 
is such that a level of safety equivalent to that established by the 
airworthiness standards for transport category airplanes is provided.

DATES: Comments must be received on or before December 23, 1996.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Office of the Assistant Chief Counsel, 
Attention: Rules Docket (ANM-7), Docket No. NM-135, 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-135. 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:
William Schroeder, FAA, Standardization Branch, ANM-113, Transport 
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue 
SW, Renton, Washington 98055-4056; telephone (206) 227-2148.

SUPPLEMENTARY INFORMATION:

Comments invited

    Interested persons are invited to participate in the making of 
these proposed special conditions by submitting such written data, 
views, or arguments as they may desire. Communications should identify 
the regulatory docket or notice 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 
before further rulemaking action is taken on this proposal. The 
proposals contained in this notice may be changed in light of the 
comments received. All comments received will be available, both before 
and after the closing date for comments, in the Rules Docket for 
examination by interested parties. A report summarizing each 
substantive public contact with FAA personnel concerning this 
rulemaking will be filed in the docket. Commenters wishing the FAA to 
acknowledge receipt of their comments submitted in response to this 
notice must include a self-addressed, stamped postcard on which the 
following statement is made: ``Comments to Docket No. NM-135.'' The 
postcard will be date stamped and returned to the commenter.

Background

    On May 25, 1993, Boeing Commercial Airplane Group-Wichita Division, 
applied for a supplemental type certificate (STC) to modify Boeing 
Model 767-27C airplanes to an Airborne Warning and Control System 
(AWACS) configuration. The AWACS modification includes installation of 
equipment consoles, seats for console operators, a liquid oxygen (LOX) 
system (liquid oxygen converter, valves, evaporating coils, lines, 
regulators, indicators, fittings, etc.), and a radome on the top of the 
airplane. Boeing will modify the aft lower lobe with hydraulics for the 
AWACS antenna drive unit, high-powered radio frequency units for the 
AWACS radar, and other AWACS hardware. Boeing has designed the LOX 
installation to allow extended unpressurized operation at 25,000 feet. 
The FAA will approve the performance of the oxygen system during 
certification testing.
    There are no specific regulations that address the design and 
installation of oxygen systems that utilize liquid oxygen. Existing 
requirements, such as Secs. 25.1309, 25.1441 (b) & (c), 25.1451, and 
25.1453 in the Boeing Model 767-27C original type certification basis, 
applicable to this modification, provide some design standards for crew 
and medical oxygen system installations. However, the FAA must specify 
additional standards for systems utilizing liquid oxygen to ensure that 
an acceptable level of safety is maintained.

Supplemental Type Certification Basis

    Under the provisions of Secs. 21.101 (a) and (b), Boeing Commercial 
Airplane Group must show that the modified Model 767-27C continues to 
meet the applicable provisions of the regulations incorporated by 
reference in Type Certificate (TC) No. A1NM, 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 
regulations incorporated by reference in TC A1NM are basically as 
follows: Part 25 of the FAR, as amended by Amendments 25-1 through 25-
37, plus certain later amended sections as specified in Type 
Certificate Data Sheet A1NM. In addition, the certification basis 
includes certain special conditions, exemptions and optional 
requirements that are not relevant to these special conditions. Also, 
the modified Model 767-27C must continue to comply with the fuel 
venting and exhaust emission requirements of part 34 (previously 
Special Aviation Regulation 27), and the noise certification 
requirements of part 36 in effect on the date the STC is issued.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended and applicable) do not contain 
adequate or appropriate safety standards for the modified Model 767-27C 
because of a novel or unusual design feature, special

[[Page 59203]]

conditions are prescribed under the provisions of Sec. 21.16.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR after public notice, as required by Sec. 11.28 
and Sec. 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 applicant apply for a supplement type 
certificate to modify any other model included on the same type 
certificate to incorporate the same novel or unusual design feature, 
the special conditions would apply to the other model under the 
provisions of Sec. 21.101(a)(1).

Discussion

    There are no specific regulations that address the design and 
installation of oxygen systems that utilize liquid oxygen for storage. 
Existing requirements, such as Secs. 25.1309, 25.1441 (b) and (c), 
25.1451, and 25.1453 of the Boeing 767-200 series certification basis 
applicable to this STC project, provide some design standards 
appropriate for oxygen system installations. However, additional design 
standards for oxygen systems utilizing liquid oxygen are needed to 
supplement the existing applicable requirements. The quantity of liquid 
oxygen involved in this installation and the potential for unsafe 
conditions that may result when the oxygen content of an enclosed area 
becomes too high because of system leaks, malfunction, or damage from 
external sources, make it necessary to assure adequate safety standards 
are applied to the design and installation of the system in Boeing 
Model 767-27C airplanes.
    To ensure that a level of safety is achieved for modified Boeing 
Model 767-27C airplanes, utilizing liquid oxygen as a storage medium 
for an oxygen system, equivalent to that intended by the regulations 
incorporated by reference, special conditions are needed which require 
those oxygen systems to be designed and installed to preclude or 
minimize the existence of unsafe conditions that can result from system 
leaks, malfunction, installation, or damage from external sources.
    Application by Boeing for approval of oxygen systems utilizing 
liquid oxygen as a storage medium installed in transport airplanes, and 
the unsafe conditions that can exist when the oxygen content of an 
enclosed area becomes too high because of system leaks, malfunction, 
installation or damage from external sources, make development and 
application of appropriate additional design and installation standards 
necessary.
    As discussed above, these special conditions are applicable 
initially to the Boeing Model 767-27C airplane. Should Boeing 
Commercial Airplane Group 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 Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of 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.

List of Subjects in 14 CFR Part 25

    Air transportation, Aircraft, Aviation safety, Safety.
    The authority citation for these special conditions continues to 
read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Boeing Model 767-27C airplanes modified to an AWACS configuration.
    a. The liquid oxygen converter and other oxygen equipment shall not 
be installed where baggage, cargo, or loose equipment are stored 
(unless items are stored within an appropriate container which is 
secured or restrained by acceptable means).
    b. The liquid oxygen converter shall be located in the aircraft so 
that there is no risk of damage due to an uncontained rotor or fan 
blade failure.
    c. The liquid oxygen system and associated gaseous oxygen 
distribution lines should be designed and located to minimize the 
hazard from uncontained rotor debris.
    d. The flight deck oxygen system shall meet the supply requirements 
of Part 121 after the distribution line has been served by a rotor 
fragment.
    e. The pressure relief values on the liquid oxygen converters shall 
be vented overboard through a drain in the bottom of the aircraft. 
Means must be provided to prevent hydrocarbon fluid migration from 
impinging upon the vent outlet of the liquid oxygen system.
    f. The system shall include provisions to ensure complete 
conversion of the liquid oxygen to gaseous oxygen.
    g. If multiple converters are used and manifolded together, check 
valves shall be installed so that a leak in one converter will not 
allow leakage of oxygen from any other converter.
    h. Flexible hoses shall be used for the aircraft systems 
connections to shock-mounted converters, where movement relative to the 
aircraft may occur.
    i. Condensation from system components or lines shall be collected 
by drip pans, shields, or other suitable collection means and drained 
overboard through a drain fitting separate from the liquid oxygen vent 
fitting, as specified in (e) above.
    j. Oxygen system components shall be burst pressure tested to 3.0 
times, and proof pressure tested to 1.5 times, the maximum normal 
operating pressure. Compliance with the requirement for burst testing 
may be shown by analysis, or a combination of analysis and test.
    k. Oxygen system components shall be electrically bonded to the 
aircraft structure.
    l. All gaseous or liquid oxygen connections located in close 
proximity to an ignition source shall be shrouded and vented overboard 
using the system specified in (e) above.
    m. A means will be provided to indicate the quantity of oxygen in 
the converter and oxygen availability to the flightcrews.

    Issue in Renton, Washington, on November 13, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate; Aircraft Certification 
Service, ANM-100.
[FR Doc. 96-29822 Filed 11-20-96; 8:45 am]
BILLING CODE 4910-13-M