Airworthiness Directives; Boeing Model 747-400 and 767-200 and - 300 Series Airplanes Powered by Pratt & Whitney Model PW4000 Series Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-208-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747-400 and 767-200 and -

300 Series Airplanes Powered by Pratt & Whitney Model PW4000 Series

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 747-400 and

767-200 and -300 series airplanes. This proposal would require

repetitive inspections to detect damage and wear of the auxiliary track

assembly of the thrust reverser, and corrective actions, if necessary.

This proposal would also

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require eventual replacement of the liner and slider, or the entire

assembly, with new, improved parts, which, when accomplished, would

terminate the repetitive inspections. This proposal is prompted by

reports of damage and wear to the auxiliary track assembly. The actions

specified by the proposed AD are intended to prevent a slider

disengaging from the auxiliary track assembly, which could lead to

separation of a portion of the thrust reverser from the airplane during

flight, possible impact of separated portions on airplane structure,

and consequent possible rapid decompression of the airplane, reduced

controllability of the airplane, or reduced structural integrity of the

fuselage.

DATES: Comments must be received by December 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 99-NM-208-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9 a.m. and 3 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: Sulmo Mariano, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (425) 227-2686; 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 99-NM-208-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. 99-NM-208-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports indicating that damage and wear was

found on the upper and lower auxiliary track assemblies of the thrust

reverser halves on Boeing Model 747 and 767 series airplanes equipped

with Pratt & Whitney Model PW4000 series engines. Further investigation

revealed that the damage and wear is caused by loss of the Rulon J tape

on the slider of the auxiliary track assembly. This condition, if not

corrected, could result in a slider disengaging from the auxiliary

track assembly, which could lead to separation of a portion of the

thrust reverser from the airplane during flight, possible impact of

separated portions on airplane structure, and consequent possible rapid

decompression of the airplane, reduced controllability of the airplane,

or reduced structural integrity of the fuselage.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-

78A2164, Revision 2, dated December 3, 1998 (for Model 747-400 series

airplanes), and Boeing Service Bulletin 767-78A0079, Revision 2, dated

December 3, 1998 (for Model 767-200 and -300 series airplanes). These

service bulletins describe procedures for repetitive inspections of the

auxiliary track assembly of the thrust reverser to detect missing

segments of the track lip; to detect signs that the slider has

disengaged from the track; to detect cracks, gouges, and wear of the

liner; and to measure the auxiliary track liner gap. The service

bulletins also describe procedures for temporary repairs and repetitive

inspections of those repairs, if necessary. The service bulletins

describe procedures for replacement of the liner and slider with a new,

improved liner and slider, installation of a retainer bar, and

replacement of the auxiliary track assembly with a new, improved

assembly. Such modifications eliminate the need for repetitive

inspections. Accomplishment of the actions specified in the applicable

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 applicable service bulletin described previously, except as

discussed below.

Differences Between Proposed Rule and Service Bulletins

Operators should note that this proposed AD would mandate, at

various compliance times depending on the findings during the

repetitive inspections, the replacement of the liner and slider, or the

entire auxiliary track assembly, with new, improved parts. Such

replacement is described in the service bulletins as optional

terminating action for the repetitive inspections.

The FAA has determined that long-term continued operational safety

will be better assured by design changes to remove the source of the

problem, rather than by repetitive inspections. Long-term inspections

may not be providing the degree of safety assurance necessary for the

transport airplane fleet. This, coupled with a better understanding of

the human factors associated with numerous continual inspections, has

led the FAA to consider placing less emphasis on inspections and more

emphasis on design improvements. The proposed replacement requirement

is consistent with these conditions.

The service bulletins describe, for certain damage or wear detected

on the auxiliary track assembly, replacement of the liner and slider

with a new, improved liner and slider, installation of a retainer bar,

and a one-time inspection of the repair as a permanent repair. The

service bulletins state that such actions would eliminate the need for

the repetitive inspections. The proposed AD would only allow this

repair as a temporary repair and would

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require eventual replacement of the repaired auxiliary track assembly

with a new, improved assembly. The FAA has determined that this repair

would not prevent excessive damage and wear in the future because the

cause of that damage and wear is related to how the parts mate during

installation, and, therefore, such repair would not prevent the subject

unsafe condition.

Cost Impact

There are approximately 254 airplanes of the affected design in the

worldwide fleet. The FAA estimates that 12 Model 747-400 series

airplanes and 46 Model 767-200 and -300 series airplanes of U.S.

registry would be affected by this proposed AD.

It would take approximately 4 work hours per engine to accomplish

the proposed repetitive inspection, at an average labor rate of $60 per

work hour. Based on these figures, the cost impact of the proposed AD

on U.S. operators of Model 747-400 series airplanes (4 engines per

airplane) is estimated to be $11,520, or $960 per airplane, per

inspection cycle. The cost impact of the proposed AD on U.S. operators

of Model 767 series airplanes (2 engines per airplane) is estimated to

be $22,080, or $480 per airplane, per inspection cycle.

Should an operator be required to accomplish the replacement of the

auxiliary track assembly, it would take approximately 220 work hours

per auxiliary track assembly to accomplish the proposed replacement, at

an average labor rate of $60 per work hour. Required parts would cost

approximately $30,090. Based on these figures, the cost impact of this

replacement is estimated to be $43,290 per assembly. There are four

auxiliary track assemblies per engine.

Should an operator be required to accomplish the replacement of the

liner and slider, it would take approximately 8 work hours per

auxiliary track assembly to accomplish the proposed replacement, at an

average labor rate of $60 per work hour. Required parts would be

provided at no cost by the airplane manufacturer. Based on these

figures, the cost impact of this replacement is estimated to be $480

per assembly. There are four auxiliary track assemblies per engine.

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 99-NM-208-AD.

Applicability: Model 747-400 series airplanes powered by Pratt &

Whitney PW4000 series engines, line numbers 696 through 1100

inclusive; and Model 767-200 and -300 series airplanes powered by

Pratt & Whitney PW4000 series engines, line numbers 1 through 646

inclusive; 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 slider disengaging from the auxiliary track

assembly, which could lead to separation of a portion of the thrust

reverser from the airplane during flight, possible impact of

separated portions on airplane structure, and consequent possible

rapid decompression of the airplane, reduced controllability of the

airplane, or reduced structural integrity of the fuselage,

accomplish the following:

Initial Inspection

(a) Prior to the accumulation of 3,000 total flight cycles, or

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

later, perform a detailed visual inspection of the upper and lower

auxiliary track assemblies on each thrust reverser half of each

engine to detect missing segments of the track lip; to detect signs

that the slider has disengaged from the track; to detect cracks,

gouges, and wear of the liner; and to measure the auxiliary track

liner gap; in accordance with Part A of the Accomplishment

Instructions of Boeing Service Bulletin 747-78A2164, Revision 2,

dated December 3, 1998 (for Model 747-400 series airplanes); or

Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3,

1998 (for Model 767 series airplanes); as applicable.

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.''

Repetitive Inspections/Corrective Actions

(1) If no discrepancy is detected, repeat the detailed visual

inspection thereafter at intervals not to exceed 3,000 flight cycles

or 7,000 flight hours, whichever occurs earlier, until paragraph (b)

or (c), as applicable, has been accomplished.

(2) If the auxiliary track lip has a missing segment of 3 inches

or longer, or longitudinal cracks at the base of the lip, or other

indications that the slider has disengaged from the track in the

forward 4 inches, prior to further flight, repair in accordance with

Part A of the Accomplishment Instructions of the applicable service

bulletin. Repeat the detailed visual inspection thereafter at the

applicable intervals specified in Part A of the Accomplishment

Instructions of the applicable service bulletin, until paragraph (c)

of this AD has been accomplished.

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(3) If the auxiliary track lip has a missing segment of 3 inches

or longer, or longitudinal cracks at the base of the lip, or other

indications that the slider has disengaged from the track AFT of the

forward four inches, accomplish paragraphs (a)(3)(i) or (a)(3)(ii)

of this AD.

(i) Prior to further flight, repair in accordance with Part A of

the Accomplishment Instructions of the applicable service bulletin.

Repeat the detailed visual inspection thereafter at the applicable

intervals specified in Part A of the Accomplishment Instructions of

the applicable service bulletin, until paragraph (c) of this AD has

been accomplished.

(ii) Accomplish both paragraphs (a)(3)(ii)(A) and (a)(3)(ii)(B)

of this AD:

(A) Prior to further flight, deactivate the associated thrust

reverser in accordance with Section 78-2 of Boeing Document

D6U10151, ``Boeing 747-400 Dispatch Deviations Guide,'' Revision 11,

dated March 31, 1998 (for Model 747-400 series airplanes); or

Section 78-2 of Boeing Document D630T002, ``Boeing 767 Dispatch

Deviations Guide,'' Revision 19, dated May 14, 1999 (for Model 767

series airplanes); as applicable. No more than one thrust reverser

on any airplane may be deactivated under the provisions of the

paragraph.

Note 3: The airplane may be operated for up to 30 days in

accordance with the provisions and limitations specified in the

operator's FAA-approved Master Minimum Equipment List, provided that

no more than one thrust reverser on the airplane is inoperative.

(B) Within 30 days after deactivation of any thrust reverser in

accordance with paragraph (a)(3)(ii)(A) of this AD, the thrust

reverser must be repaired in accordance with Part A of the

Accomplishment Instructions of the applicable service bulletin; once

this is accomplished, the thrust reverser may then be reactivated.

Repeat the detailed visual inspection thereafter at the applicable

intervals specified in Part A of the Accomplishment Instructions of

the applicable service bulletin, until paragraph (c) of this AD has

been accomplished.

Terminating Action

(b) For any auxiliary track assembly on which no discrepancy is

detected during any detailed visual inspection required by paragraph

(a) of this AD: Replace the liner and slider of the auxiliary track

assembly with a new, improved liner and slider, in accordance with

Part A of the Accomplishment Instructions of Boeing Service Bulletin

747-78A2164, Revision 2, dated December 3, 1998 (for Model 747-400

series airplanes); or Boeing Service Bulletin 767-78A0079, Revision

2, dated December 3, 1998 (for Model 767 series airplanes); as

applicable; at the later of the times specified in paragraphs (b)(1)

and (b)(2) of this AD. Such action constitutes terminating action

for the requirements of this AD for that assembly.

(1) Within 6,000 flight cycles, 14,000 flight hours, or 5 years

after the date of the first inspection, whichever occurs earliest;

or

(2) Within 4 years after the effective date of this AD.

(c) For any auxiliary track assembly on which any discrepancy is

detected during any detailed visual inspection required by paragraph

(a) of this AD: Replace the auxiliary track assembly with a new,

improved assembly (including a new liner and slider), in accordance

with Part A of the Accomplishment Instructions of Boeing Service

Bulletin 747-78A2164, Revision 2, dated December 3, 1998 (for Model

747-400 series airplanes); or Boeing Service Bulletin 767-78A0079,

Revision 2, dated December 3, 1998 (for Model 767 series airplanes);

as applicable; at the later of the times specified in paragraphs

(c)(1) and (c)(2) of this AD. Such action constitutes terminating

action for the requirements of this AD for that assembly.

(1) Within 4,500 flight cycles, 10,000 flight hours, or 3 years

after the date of the first repair, whichever occurs earliest; or

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

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 4: 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 October 13, 1999.

D.L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-27273 Filed 10-18-99; 8:45 am]

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