[Federal Register Volume 60, Number 106 (Friday, June 2, 1995)]
[Proposed Rules]
[Pages 28763-28764]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-13503]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-28-AD]


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to all Boeing Model 737 series 
airplanes. This proposal would require revising the FAA-approved 
Airplane Flight Manual (AFM) to provide the flightcrew with additional 
procedures for shutting down the auxiliary power unit (APU) when an APU 
fire is indicated. This proposal is prompted by reports indicating that 
a latent electrical failure exists in the fire extinguishing system for 
the APU; this failure could prevent the APU from shutting down and fire 
extinguishant from discharging into the APU compartment in the event of 
an APU fire. The actions specified by the proposed AD are intended to 
ensure that the flightcrew is provided with procedures for shutting 
down the APU in the event of an APU fire.

DATES: Comments must be received by July 31, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-28-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.

FOR FURTHER INFORMATION CONTACT: Stephen Bray, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2681; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-NM-28-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 95-NM-28-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA received two reports indicating that a latent electrical 
failure exists in the fire extinguishing system of the auxiliary power 
unit (APU) on Boeing Model 737 series airplanes. The FAA-approved 
Airplane Flight Manual (AFM) for these airplanes currently contains 
procedures that require the flightcrew to pull and rotate the flight 
compartment fire handle when an APU fire is indicated. When the 
flightcrew takes such action, the APU shuts down and fire extinguishant 
discharges into the APU compartment. However, if a latent electrical 
failure exists in the fire extinguishing system of the APU, this 
failure could prevent the APU from shutting down and fire extinguishant 
from discharging when the flightcrew pulls and rotates the fire handle. 
A latent electrical failure in the fire extinguishing system of the 
APU, if not corrected, could result in the inability of the flightcrew 
to extinguish an APU fire.
    In light of this information, the FAA finds that the procedures 
specified [[Page 28764]] currently in the FAA-approved AFM for 
flightcrew response to an APU fire on Model 737 series airplanes are 
not defined adequately. The FAA has determined that the FAA-approved 
AFM for these airplanes must be revised to provide procedures for the 
flightcrew to turn the APU switch to the ``OFF'' position, as well as 
pulling and rotating the fire handle, when an APU fire is indicated. 
Such action will ensure that the flightcrew is able to shut down the 
APU in the event of an APU fire.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require revising the Emergency Procedures and 
Limitations Sections of the FAA-approved AFM to provide the flightcrew 
with these additional procedures for shutting down the APU when an APU 
fire is indicated.
    There are approximately 2,602 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 1,072 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 1 work hour per airplane to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Based on these figures, the total cost impact of the proposed AD on 
U.S. operators is estimated to be $64,320, or $60 per airplane.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:
PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 95-NM-28-AD.

    Applicability: All Model 737 series airplanes, certificated in 
any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To ensure that the flightcrew is provided with additional 
procedures necessary for shutting down the auxiliary power unit 
(APU) in the event of an APU fire, accomplish the following:
    (a) Within 6 months after the effective date of this AD, revise 
the Emergency Procedures and Limitations Sections of the FAA-
approved Airplane Flight Manual (AFM) to include the following 
procedures, which will ensure that the flightcrew is able to shut 
down the APU when an APU fire is indicated. This may be accomplished 
by inserting a copy of this AD in the AFM.

                           ``APU FIRE WARNING                           
RECALL                                                                  
APU Fire Warning Switch...........................  PULL AND ROTATE     
APU Switch........................................  OFF                 
REFERENCE                                                               
Master Fire Warning...............................  RESET''             
                                                                        

    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Operations Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (c) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on May 26, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-13503 Filed 6-1-95; 8:45 am]
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