[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
