[Federal Register Volume 60, Number 198 (Friday, October 13, 1995)]
[Proposed Rules]
[Pages 53307-53308]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-25451]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-117-AD]


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
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 certain Boeing Model 737-300, -
400, and -500 series airplanes. This proposal would require inspection 
for damage of a wire bundle and clamp that are located in the 
electronic/electrical (E/E) equipment bay, and repair of any damaged 
wire bundle or clamp. This proposal also would require replacement of 
the existing steel clamp with a nylon clamp, and rearrangement of the 
clamp installation. This proposal is prompted by a report of fire in 
the E/E equipment bay due to electrical arcing caused by chafing of a 
wire bundle. The actions specified by the proposed AD are intended to 
prevent chafing of a wire bundle that could cause short circuiting of 
the wire bundle, and could result in smoke and fire in the E/E 
equipment bay.

DATES: Comments must be received by December 11, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-117-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.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207.
    This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Stephen Oshiro, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (206) 227-2793; 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-117-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-117-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report indicating that six circuit breakers 
tripped during a flight of a Boeing Model 737-300 series airplanes, and 
that shortly after landing, maintenance personnel discovered smoke and 
flames coming from the insulation blanket at the left side of the 
electronic/electrical (E/E) equipment bay. Investigation revealed the 
source of ignition to be electrical arcing caused by chafing of a wire 
bundle by a wire bundle clamp at body station (BS) 360, water line (WL) 
200, left buttock line (LBL) 55. Tension in the wire bundle caused 
deformation of the rubber cushioning material surrounding the metal 
portion of the clamp. Short circuiting and the resultant electrical 
arcing occurred when the metal portion of the clamp chafed through the 
insulation on the wires. Further investigation revealed that the wire 
bundle had been incorrectly routed and improperly clamped at the time 
of original manufacture. Improper clamping of the wire bundle resulted 
from the use of a rubber cushioned metal clamp instead of the nylon 
clamp specified by the design data. These conditions, if not corrected, 
could cause a fire and smoke in the E/E equipment bay, as a result of 
short circuiting of the wire bundle.
    The FAA has reviewed Boeing Service Letter 737-SL-24-106, dated 
March 10, 1995, which describes procedures for performing a visual 
inspection for damage of the wire bundle and the clamp that contains 
the wire bundle in the E/E equipment bay, and repair, if necessary. 
Additionally, the service letter describes procedures to reclamp wire 
bundle W2132 (or W0132) by removing the rubber cushioned steel clamp 
and installing a nylon clamp on the aft side of the existing nut and 
bolt hole at BS 360, WL 203, LBL 57. The service letter also describes 
procedures for installing the clamps in a new arrangement as a 
precaution to prevent contact at the crossover point between wire 
bundle W2132 (or W0132) and W0142, the power feed wire bundle.
    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 a visual inspection for damage of the wire 
bundle and clamp in the E/E equipment bay, and repair, if necessary. 
Additionally, the proposed AD would require replacement of the rubber 
cushioned steel clamp with a nylon clamp, and the installation of 
additional clamps to prevent contact 

[[Page 53308]]
between W2132 (or W0132) and power feeder wire bundle W0142. These 
actions would be required to be accomplished in accordance with the 
service letter described previously.
    Operators should note that replacement of the steel clamp with the 
nylon clamp and the installation of additional clamps to prevent 
contact between W2132 (or W0132) and power feeder wire bundle W0142 are 
specified as ``recommended actions'' in the referenced Boeing service 
letter. However, this proposed rule would mandate accomplishment of 
those actions. The FAA finds that those actions must be accomplished in 
order to provide an adequate level of safety for the affected fleet. 
The FAA has determined that, in cases where certain known unsafe 
conditions exist, and where actions to detect and correct that unsafe 
condition can be readily accomplished, those actions must be required.
    The proposed AD also would require that operators submit a report 
of any damage found during the inspection that would be required by 
this proposed AD. The information obtained from these reports will 
enable the FAA to determine how widespread any damage is in the fleet.
    There are approximately 620 Model 737-300, -400, and -500 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 195 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. Required parts would cost approximately $25 per 
airplane. Based on these figures, the total cost impact of the proposed 
AD on U.S. operators is estimated to be $16,575, or $85 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 USC 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

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

Boeing: Docket 95-NM-117-AD.

    Applicability: Model 737-300, -400, and -500 series airplanes, 
as listed in Boeing Service Letter 737-SL-24-106, dated March 10, 
1995; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must use the authority 
provided in paragraph (c) of this AD to request approval from the 
FAA. This approval may address either no action, if the current 
configuration eliminates the unsafe condition; or different actions 
necessary to address the unsafe condition described in this AD. Such 
a request should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent short circuiting of a wire bundle located in the 
electrical/electronics (E/E) equipment bay, which could result in 
smoke and fire, accomplish the following:
    (a) Within 12 months after the effective date of this AD, 
accomplish the requirements of paragraphs (a)(1), (a)(2), and 
(a)(3), of this AD in accordance with Boeing Service Letter 737-SL-
24-106, dated March 10, 1995.
    (1) Perform a visual inspection for damage of the wire bundle 
and clamps in the E/E compartment. If any damage is detected, prior 
to further flight, repair in accordance with the service letter.
    (2) Reclamp wire bundle W2132 (or W0132) by removing the steel 
cushioned clamp and installing nylon clamp on the aft side of the 
existing nut and bolt hole at body station (BS) 360, water line (WL) 
203, left buttock line (LBL) 57, in accordance with the service 
letter.
    (3) Install additional clamps to wire bundles W2132 (or W0132) 
and power feeder wire bundle WO142, in accordance with the service 
letter.
    (b) Within 10 days after detecting any damage to the wire bundle 
or clamp as a result of the inspection required by paragraph (a) of 
this AD, submit a report of the damage findings to the FAA, 
Transport Airplane Directorate, Seattle Manufacturing Inspection 
District Office (MIDO), Attention: George Carter, 1601 Lind Avenue 
SW., Renton, Washington 98055-4056; telephone (206) 237-6229; fax 
(206) 965-0264. Information collection requirements contained in 
this regulation have been approved by the Office of Management and 
Budget (OMB) under the provisions of the Paperwork Reduction Act of 
1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control 
Number 2120-0056.
    (c) 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 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) 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 October 6, 1995.
Gary L. Killion,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-25451 Filed 10-12-95; 8:45 am]
BILLING CODE 4910-13-U