[Federal Register Volume 59, Number 78 (Friday, April 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-9729]


[[Page Unknown]]

[Federal Register: April 22, 1994]


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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]
BILLING CODE 4910-13-U