Airworthiness Directives; Boeing Model 747-400 Series Airplanes Equipped With Pratt & Whitney PW4000 Series Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-37-AD]

Airworthiness Directives; Boeing Model 747-400 Series Airplanes

Equipped With Pratt & Whitney 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

series airplanes. This proposal would require replacement of the thrust

reverser flow restrictor devices with one-way (check) valve

restrictors. This proposal is prompted by reports of actuator piston

seal leakage found during actuator overhaul on certain Model 747-400

series airplanes. The actions specified by the proposed AD are intended

to prevent possible deployment of a thrust reverser in flight and

subsequent reduced controllability of the airplane.

DATES: Comments must be received by June 20, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-37-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: Jon Regimbal, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2687; 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 94-NM-37-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. 94-NM-37-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports of actuator piston seal leakage found

during actuator overhaul on Model 747-400 series airplanes equipped

with Pratt & Whitney PW4000 series engines. No reports of thrust

reverser sleeve deployment due to this leakage have been received;

however, testing by the airplane manufacturer suggests that if

sufficient seal leakage occurs in the locking actuator on a single

thrust reverser sleeve, that sleeve could deploy.

The deploy and stow sides of the thrust reverser actuator are

separated by a piston seal. During reverser stow, or during an

occurrence of auto-restow, leakage of this seal can allow hydraulic

fluid to pass from the stow side of the actuator to its deploy side. If

this leakage is sufficient, a flow control/restrictor device in the

hydraulic line can subsequently cause back pressure to build up in the

deploy side of the actuator. In such cases, the sleeve could unlock and

deploy. This condition, if not corrected, could result in reduced

controllability of the airplane.

The FAA has reviewed and approved Boeing Alert Service Bulletin

747-78A2128, dated March 10, 1994, that describes procedures for

replacement of the thrust reverser flow restrictor devices with one-way

(check) valve restrictors. Accomplishment of this replacement will

prevent uncommanded deployment of a single thrust reverser sleeve

(``half'') caused by leakage of the piston seals in the thrust reverser

sleeve actuators.

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 replacement of the thrust reverser flow

restrictor devices with one-way (check) valve restrictors. The actions

would be required to be accomplished in accordance with the alert

service bulletin described previously.

There are approximately 94 Model 747-400 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 32

airplanes of U.S. registry would be affected by this proposed AD, that

it would take approximately 24 work hours per airplane to accomplish

the proposed actions, and that the average labor rate is $55 per work

hour. Required parts would be supplied by the manufacturer at no cost

to operators. Based on these figures, the total cost impact of the

proposed AD on U.S. operators is estimated to be $42,240, or $1,320 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 14

CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Boeing: Docket 94-NM-37-AD.

Applicability: Model 747-400 series airplanes up to and

including line position 1022, equipped with Pratt & Whitney PW4000

series engines, certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent possible deployment of a thrust reverser in flight

and subsequent reduced controllability of the airplane, accomplish

the following:

(a) Within 18 months after the effective date of this AD,

replace the thrust reverser flow restrictor devices with one-way

(check) valve restrictors in accordance with Boeing Alert Service

Bulletin 747-78A2128, dated March 10, 1994.

(b) 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: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(c) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) 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 April 18, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-9729 Filed 4-21-94; 8:45 am]

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