Airworthiness Directives; Boeing Model 767 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-316-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

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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 767 series

airplanes. This proposal would require repetitive inspections to detect

discrepancies of the wiring and surrounding Teflon sleeves of the fuel

tank boost pumps and override/jettison pumps; replacement of the

sleeves with new sleeves, for certain airplanes; and repair or

replacement of the wiring and sleeves with new parts, as necessary.

This proposal is prompted by reports of chafing of Teflon sleeves that

surround and protect electrical wires inside conduits installed in the

fuel tanks. The actions specified by the proposed AD are intended to

ensure adequate protection to the fuel pump wire insulation. Such

chafing of the wire insulation could eventually result in exposure of

electrical conductor, permit arcing from the wire to the conduit, and

create a potential for a fuel tank fire or explosion.

DATES: Comments must be received by December 30, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 98-NM-316-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: Holly Thorson, Aerospace Engineer,

Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,

Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (425) 227-1357; fax (425) 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 98-NM-316-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-114, Attention: Rules

Docket No. 98-NM-316-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

Inspections of Boeing Model 747 series airplanes were performed in

accordance with AD 96-26-06, amendment 39-9870 (62 FR 304, January 3,

1997), and AD 97-26-07, amendment 39-10250 (62 FR 65352, December 12,

1997), to detect damage of the sleeving and wire bundles of certain

fuel tank boost pumps and auxiliary jettison pumps. The inspections

revealed significant chafing through the Teflon sleeves that enclose

wire bundles inside the conduits located in the fuel tanks.

As on Model 747 series airplanes, the Model 767 fuel pumps for the

main fuel tanks and the center wing tank (auxiliary tank) are supplied

electrical power by wiring encased in metal conduits inside the fuel

tanks; a wire bundle is separated from its associated conduit by two

concentric Teflon sleeves. Moreover, the vibration environments in the

wing fuel tanks of Model 747 and 767 series airplanes are similar.

Therefore, the wear rate of the Teflon sleeves surrounding the

electrical wires could be similar for Model 747 and 767 series

airplanes.

Because the unsafe condition identified in AD 96-26-06 and AD 97-

26-07 for Model 747 series airplanes (the potential for fuel tank fire

or explosion due to chafing) is also likely to occur on Model 767

series airplanes, procedures were developed (and are described below)

for the inspection of fuel tank wire bundles and Teflon sleeves on

Model 767 series airplanes. As part of the validation process for the

development of the service bulletin for those procedures, the wire

bundles and sleeves were inspected on several Model 767 series

airplanes. The inspections revealed numerous cases of chafing through

the outer Teflon sleeves and three cases of chafing through both Teflon

sleeves. There were no reports of damage to the wire insulation or

jacket. Several variations in the sleeve installations were reported,

including one report of a missing outer sleeve and another report of

sleeves too thin to meet required criteria. Numerous occurrences of

spliced sleeve sections were noted; several of those spliced sections

were separated, leaving 1- to 2-inch gaps in the sleeves and exposing

the wires. All of the operators that conducted the preliminary

inspections reported that lacing ties were installed at approximately

6-inch intervals around the outside of the sleeves. Lacing ties

installed on the outside of the sleeves (except at the conduit ends)

may contribute to the degradation of the sleeves. Damaged or spliced

Teflon sleeves could result in chafing of the electrical wiring in the

fuel tank conduits and thereby expose the electrical conductor.

Exposure of the electrical conductor, if not corrected, could permit

arcing from the wire to the conduit and create a potential for a fuel

tank fire or explosion.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin

767-28A0053, Revision 1, dated August 5, 1999, which describes

procedures for repetitive visual inspections to detect damage of the

Teflon sleeves surrounding fuel tank boost pump and override/jettison

pump wiring; and a follow-on visual inspection to detect damage of the

wiring and corrective actions, if necessary. The corrective actions

include replacing discrepant Teflon sleeves (having splices, cuts,

splits, holes, worn areas, or lacing ties installed on the outside of

the sleeves) with new Teflon sleeves, replacing wiring that has been

damaged due to arcing, and repairing or replacing wiring that has been

damaged for reasons other than arcing. Accomplishment of the actions

specified in the alert service bulletin is intended to adequately

address the identified unsafe condition.

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FAA's Findings

The FAA has determined that splicing the Teflon sleeves at any

location along the length of the wire bundle is unacceptable because

spliced sections may pull apart, leaving gaps in the sleeves and

portions of the wires unprotected from chafing against the conduit.

Additionally, the FAA has determined that lacing ties installed around

the sleeves may contribute to the chafing of the sleeves. In light of

these findings and the demonstrated need for protective Teflon sleeves

between the wires and the conduits inside the fuel tanks, the FAA has

concluded that an inspection of all Model 767 series airplanes is

required to determine the integrity of the installed Teflon sleeves and

wire bundles.

Explanation of Requirements of Proposed Rule

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 accomplishment of the actions specified in

the alert service bulletin described previously, except as discussed

below. The proposed AD also would require that operators report

positive inspection findings (findings of discrepancies only) to the

FAA.

Differences Between Proposed AD and Relevant Service Information

Operators should note that, while Boeing Alert Service Bulletin

767-28A0053 limits its effectivity to Boeing Model 767 series airplanes

having certain line numbers, this proposed AD would be applicable to

all Model 767 series airplanes. The FAA has determined that all Model

767 series airplanes are subject to the unsafe condition.

Clarification of Service Bulletin Figure

The FAA finds it necessary to clarify the note inserted between

steps 6 and 7 in Figure 2, Sheet 4, of the alert service bulletin.

Where the alert service bulletin refers to ``damage'' as ``more than

one piece of sleeve,'' this type of ``damage'' is intended to refer to

splices in the protective Teflon sleeves. Splices are considered

``damage'' because they may become pulled apart, potentially exposing

the underlying wires and leaving them unprotected from chafing against

the conduit.

Cost Impact

There are approximately 716 airplanes of the affected design in the

worldwide fleet. The FAA estimates that 253 airplanes of U.S. registry

would be affected by this proposed AD. It would take approximately 5

work hours per airplane (for airplanes with jettison pumps) or 3 work

hours per airplane (for airplanes without jettison pumps) to accomplish

the proposed inspection/replacement, at an average labor rate of $60

per work hour. Parts, if required, would cost $336 for the sleeve

replacement proposed by this AD.

Based on these figures, the cost impact of the proposed AD on U.S.

operators is estimated to be $636 or $516 per airplane, if required to

accomplish the replacement action; and $300 or $180 per airplane, per

inspection cycle.

The cost impact figures discussed above are 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.

Regulatory Impact

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. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Boeing: Docket 98-NM-316-AD.

Applicability: All Model 767 series airplanes, 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 request approval for an

alternative method of compliance in accordance with paragraph (e) of

this AD. The request should include an assessment of the effect of

the modification, alteration, or repair on the unsafe condition

addressed by this AD; and, if the unsafe condition has not been

eliminated, the request should include specific proposed actions to

address it.

Compliance: Required as indicated, unless accomplished

previously.

To prevent exposure of the electrical conductor, which could

permit arcing from the wire to the conduit and create a potential

for a fuel tank fire or explosion, accomplish the following:

Inspection

1(a) Perform a detailed visual inspection to detect

discrepancies--including the presence of splices, cuts, splits,

holes, worn areas, and lacing ties installed on the outside of the

sleeves (except at the sleeve ends) of the Teflon sleeves

surrounding the wiring of the fuel tank boost pumps and override/

jettison pumps, at the earlier of the times specified in paragraphs

(a)(1) and (a)(2) of this AD, in accordance with Boeing Alert

Service Bulletin 767-28A0053, Revision 1, dated August 5, 1999.

Repeat the inspection thereafter at intervals not to exceed 60,000

flight hours or 30,000 flight cycles, whichever occurs first.

(1) Prior to the accumulation of 50,000 total flight hours, or

within 90 days after the effective date of this AD, whichever occurs

later.

(2) Within 18 months after the effective date of this AD.

Note 2: For the purposes of this AD, a detailed visual

inspection is defined as: ``An intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc. may be used. Surface cleaning and

elaborate access procedures may be required.''

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Corrective Actions

(b) If any discrepancy is detected during any inspection

required by paragraph (a) of this AD: Prior to further flight,

remove the Teflon sleeves and perform a detailed visual inspection

to detect damage of the wiring, in accordance with paragraph D. of

the Accomplishment Instructions of Boeing Alert Service Bulletin

767-28A0053, Revision 1, dated August 5, 1999.

(1) If no damage to the wiring is detected, prior to further

flight, install new Teflon sleeves in accordance with the alert

service bulletin.

(2) If any damage to the wiring is detected, prior to further

flight, accomplish the requirements of paragraph (c) of this AD.

(c) If any damage to the wiring is detected during any

inspection required by paragraph (b) of this AD: Prior to further

flight, perform a detailed visual inspection to determine if the

wiring damage was caused by arcing, in accordance with paragraph D.

of the Accomplishment Instructions of Boeing Alert Service Bulletin

767-28A0053, Revision 1, dated August 5, 1999.

(1) If the wire damage was not caused by arcing: Prior to

further flight, repair any damaged wires or replace the wires with

new or serviceable wires, as applicable, and install new Teflon

sleeves; in accordance with the alert service bulletin.

(2) If any damage caused by arcing is found: Prior to further

flight, perform an inspection for signs of fuel inside the conduit

or on the wires, in accordance with the alert service bulletin.

(i) If no sign of fuel is found, accomplish the actions

specified by paragraphs (c)(2)(i)(A), (c)(2)(i)(B), (c)(2)(i)(C),

and (c)(2)(i)(D) of this AD.

(A) Prior to further flight, repair the wires or replace the

wires with new or serviceable wires, as applicable, in accordance

with the alert service bulletin.

(B) Prior to further flight, install new Teflon sleeves, in

accordance with the alert service bulletin.

(C) Repeat the inspection for signs of fuel inside the conduit

thereafter at intervals not to exceed 500 flight hours, until the

requirements of paragraph (c)(2)(i)(D) have been accomplished. If

any fuel is found inside the conduit during any inspection required

by this paragraph, prior to further flight, replace the conduit with

a new or serviceable conduit in accordance with the alert service

bulletin. Thereafter, repeat the inspection specified in paragraph

(a) at intervals not to exceed 60,000 flight hours or 30,000 flight

cycles, whichever occurs first.

(D) Within 6,000 flight hours or 18 months after the initial

fuel inspection specified by paragraph (c)(2) of this AD, whichever

occurs first, replace the conduit with a new or serviceable conduit,

in accordance with the alert service bulletin. Such conduit

replacement constitutes terminating action for the repetitive fuel

inspections required by paragraph (c)(2)(i)(C) of this AD.

(ii) If any fuel is found in the conduit or on any wire: Prior

to further flight, replace the conduit with a new or serviceable

conduit, replace damaged wires with new or serviceable wires, and

install new Teflon sleeves; in accordance with the alert service

bulletin. Thereafter, repeat the inspection specified in paragraph

(a) at intervals not to exceed 60,000 flight hours or 30,000 flight

cycles, whichever occurs first.

Pump Retest

(d) For any wire bundle removed and reinstalled during any

inspection required by this AD: Prior to further flight after such

reinstallation, retest the fuel pump in accordance with paragraph

G., H., I., or J., as applicable, of the Accomplishment

Instructions, of Boeing Alert Service Bulletin 767-28A0053, Revision

1, dated August 5, 1999.

Reporting Requirement

(e) Submit a report of positive inspection findings (findings of

discrepancies only), along with any damaged wiring and sleeves, to

the Seattle Manufacturing Inspection District Office (MIDO), 2500

East Valley Road, Suite C-2, Renton, Washington 98055-4056; fax

(425) 227-1159; at the applicable time specified in paragraph (e)(1)

or (e)(2) of this AD. The report must include the airplane serial

number; the number of total flight hours and flight cycles on the

airplane; the location of the electrical cable on the airplane; and

a statement indicating whether any wire has ever been removed and

inspected during maintenance, along with the date (if known) of any

such inspection. 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.

(1) For airplanes on which the initial inspection required by

paragraph (a) of this AD is accomplished after the effective date of

this AD: Submit the report within 10 days after performing the

initial inspection.

(2) For airplanes on which the initial inspection required by

paragraph (a) of this AD has been accomplished prior to the

effective date of this AD: Submit the report for the initial

inspection within 10 days after the effective date of this AD.

Alternative Methods of Compliance

(f) 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 3: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

Special Flight Permits

(g) 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 November 5, 1999.

N. B. Martenson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-29742 Filed 11-12-99; 8:45 am]

BILLING CODE 4910-13-P