Airworthiness Directives; Boeing Model 757 Series Airplanes Equipped with Rolls Royce Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-271-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 757 Series Airplanes

Equipped with Rolls Royce Engines

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 757 series

airplanes. This proposal would require repetitive inspections to detect

wire chafing of the left and right engine fuel shutoff valve wire

bundles at Power Plant Station 278 on each engine strut, and repair if

necessary. This proposal would also require repetitive replacement of

three wire support brackets with improved wire support brackets. This

proposal is prompted by reports that such wire support brackets failed

due to fatigue, which subsequently caused the fuel shutoff valve wire

to chafe and to experience a short circuit. The actions specified by

the proposed AD are intended to prevent such conditions, which could

result in either the possible ignition of fuel vapors in a flammable

leakage zone or in the inability to stop the flow of fuel in the event

of an engine fire.

DATES: Comments must be received by September 17, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 8-NM-271-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 S. Oshiro, Aerospace Engineer,

Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane

Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,

SW., Renton, Washington 98055-4056; telephone (425) 227-2793; 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-271-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-271-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports indicating that one operator has

experienced several incidents of ``tripped'' circuit breakers. These

circuit breakers are part of the electrical circuit that controls the

activation of the engine fuel shutoff valves. Later investigation

revealed that the brackets that support the engine fuel shutoff valve

wire bundle had failed due to fatigue. The bracket failures allowed a

fuel shutoff wire bundle to chafe against the hole through which the

wire bundle passes. The chafing of the wire bundle eventually resulted

in exposure of an electrical conductor. This in turn led to a short

circuit, after which the affected engine fuel valve shutoff circuit

became disabled. The brackets are located at Power Plant Station 278,

which is located in an area of the strut that is considered to be a

``flammable leakage zone.'' This condition, if not corrected, could

result in either the possible ignition of fuel vapors in a flammable

leakage zone or in the inability to stop the flow of fuel in the event

of an engine fire.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 757-54-

0013, Revision 3, dated October 23, 1997, which describes procedures

for repetitive inspections of the wire support brackets to detect

fatigue cracking, and corrective actions if necessary. The service

bulletin also describes procedures for replacing the existing brackets

with new, improved brackets. Such replacement would eliminate the need

to continue performing the repetitive inspections specified above.

Accomplishment of the actions specified in the service bulletin is

intended to adequately address the identified unsafe condition.

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 service bulletin described previously, except as discussed below.

[[Page 42051]]

Differences Between Proposed Rule and Service Bulletin

Operators should note that the service bulletin does not specify

compliance times for accomplishing the initial and repeat inspections

of the wire support brackets, nor does it specify a compliance time for

replacing these brackets. The FAA has determined that a 12-month

initial inspection compliance time and a repetitive inspection interval

that is not to exceed 12 months would address the identified unsafe

condition in a timely manner. In developing an appropriate compliance

time for this AD, the FAA considered not only the manufacturer's

recommendation, but the degree of urgency associated with addressing

the subject unsafe condition, the average utilization of the affected

fleet, and the time necessary to perform the modification.

In addition, Boeing has failed to establish the expected fatigue

life of the new, improved wire support brackets to the FAA's

satisfaction. The brackets installed per Revision 3 to the service

bulletin are the latest of three designs, each of which was intended to

correct the problem of bracket failure. However, both of the two

previous bracket designs installed per earlier revisions to the service

bulletin also proved to be susceptible to fatigue failure. Thus,

because this design feature was historically prone to failure, this

proposed AD would require that the wire support brackets installed in

accordance with Revision 3 of the service bulletin be replaced at 12-

month intervals--i.e., at the same time the wire bundles are inspected.

This interval is shorter than the actual life of the previously failed

brackets.

Operators also should note that this proposed AD would require

operators to replace all three wire support brackets on each strut of

all affected airplanes, whereas the service bulletin recommends that

operators replace brackets on only certain airplanes. The proposed AD

would require more replacements because the expected fatigue life of

the bracket is not well established.

Finally, operators should note that, for the reason given above,

this proposed AD would require inspections of the wire bundles that

pass through the three wire support brackets on each strut to detect

wire chafing, whereas the service bulletin recommends inspection only

if a wire support bracket is cracked or broken.

Cost Impact

There are approximately 501 airplanes of the affected design in the

worldwide fleet. The FAA estimates that 249 airplanes of U.S. registry

would be affected by this proposed AD.

It would take approximately 6 work hours per airplane to accomplish

the proposed replacement and approximately 2 work hours to accomplish

the proposed inspection. The average labor rate is estimated to be $60

per work hour. Required parts would cost approximately $525 per

airplane per replacement cycle. Based on these figures, the cost impact

of the proposed AD on U.S. operators is estimated to be $250,245, or

$1,005 per airplane, per inspection/replacement 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-271-AD.

Applicability: Model 757 series airplanes equipped with Rolls

Royce engines, 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 (d) 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 a short circuit that could result in either the

possible ignition of fuel vapors in a flammable leakage zone or in

the inability to stop the flow of fuel in the event of an engine

fire, accomplish the following:

Corrective Action

(a) Within 12 months after the effective date of this AD,

accomplish paragraphs (a)(1) and (a)(2) of this AD. Thereafter,

repeat paragraphs (a)(1) and (a)(2) at intervals not to exceed 12

months.

(1) Accomplish a detailed visual inspection of the wire bundles

that pass through the three wire support brackets located at Power

Plant Station (PPS) 278 on each engine strut, to detect wire

chafing.

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.''

(2) Replace all three existing wire support brackets located at

PPS 278 on each engine strut with improved wire support brackets, in

accordance with Boeing Service Bulletin 757-54-0013, Revision 3,

dated October 23, 1997.

(b) During any inspection performed in accordance with paragraph

(a) of this AD, if

[[Page 42052]]

any wire bundle is found to be chafed, prior to further flight,

repair the wire bundle in accordance with the Boeing Standard Wiring

Practices Manual, Document D6-54446, Revision 23, dated August 1998.

Spares Paragraph

(c) As of the effective date of this AD, no person shall install

a wire support bracket having P/N 287N1112-8, -9, -20, or -21 on any

airplane.

Alternative Methods of Compliance

(d) 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

(e) 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 July 27, 1999.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-19810 Filed 8-2-99; 8:45 am]

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