[Federal Register Volume 60, Number 61 (Thursday, March 30, 1995)]
[Proposed Rules]
[Pages 16392-16395]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-7781]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-06-AD]


Airworthiness Directives; Boeing Model 747 SP, SR, -100, -200, 
and -300 Series Airplanes Equipped With Pratt & Whitney Model JT9D 
Series Engines (Excluding Model JT9D-70 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 SP, SR, -
100, -200, and -300 series airplanes. This proposal would require 
repetitive operational tests of the reversible gearbox pneumatic drive 
unit (PDU) or the reversing air motor PDU to ensure that the unit can 
restrain the thrust reverser sleeve, and correction of any discrepancy 
found. This proposal is prompted by the results of an investigation, 
which revealed that, in the event of thrust reverser deployment during 
high-speed climb or during cruise, these airplanes could experience 
control problems. The actions specified by the proposed AD are intended 
to ensure the integrity of the fail safe features of the thrust 
reverser system by preventing possible failure modes in the thrust 
reverser control system that can result in inadvertent deployment of a 
thrust reverser during flight.

DATES: Comments must be received by May 24, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-06-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 [[Page 16393]] Airplane Directorate, 1601 Lind Avenue, SW., 
Renton, Washington.

FOR FURTHER INFORMATION CONTACT: G. Michael Collins, Aerospace 
Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (206) 227-2689; 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 95-NM-06-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. 95-NM-06-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    In May 1991, a Boeing Model 767 series airplane was involved in an 
accident in which a thrust reverser deployed inadvertently during 
flight. While the investigation of the accident has not revealed the 
cause of that deployment, it has identified a number of possible 
failure modes in the thrust reverser control system. Inadvertent 
deployment of a thrust reverser during flight could result in reduced 
controllability of the airplane.
    The FAA and the aviation industry are conducting an in-depth 
investigation of the thrust reverser systems installed on various types 
of large transport airplanes. In particular, this investigation has 
focused on airplane controllability in the event of an in- flight 
deployment of a thrust reverser, and thrust reverser reliability in 
general. Based on the data gathered from this ongoing investigation, 
the FAA issued several airworthiness directives (AD) to require 
periodic inspections and tests of the thrust reverser systems on 
certain Boeing Model 757 and 767 series airplanes [for example, 
reference AD 91-20-09, amendment 39-8043 (56 FR 46725, September 16, 
1991) for certain Model 757 series airplanes; and AD 92-24-03, 
amendment 39-8408 (57 FR 53258, November 9, 1992) for certain Model 767 
series airplanes]. In addition, the FAA has issued or proposed several 
AD's to require an additional locking device on thrust reversers that 
are installed on Model 737-300/-400/-500, 757, and 767 series airplanes 
[for example, reference AD 94-14-02, amendment 39-8954 (59 FR 33646, 
June 30, 1994) for certain Model 757 series airplanes; and AD 94-16-03, 
amendment 39-8993 (59 FR 41229, August 11, 1994) for certain Model 767 
series airplanes]. These actions were taken to enhance the level of 
reliability on airplane models that were determined to have 
unacceptable flight characteristics following an in-flight deployment 
of a thrust reverser.
    Until now, the investigation of thrust reverser system reliability 
on Boeing Model 747 series airplanes has not been given as high a 
priority as the other Boeing models because Model 747 series airplanes 
have never experienced control problems as a result of an in-flight 
thrust reverser deployment. Based on this long safety record and the 
available evidence up to this time, it has been accepted generally that 
all Model 747 series airplanes would be shown to be controllable 
throughout the flight envelope following an in-flight thrust reverser 
deployment.
    Boeing has responded to an FAA request for further investigation to 
determine the controllability of Model 747 series airplanes following 
an in-flight thrust reverser deployment. The investigation results 
indicate that Model 747 SP, SR, -100, -200, -300, and -400 series 
airplanes could experience certain control problems in the event of a 
thrust reverser deployment occurring during high-speed climb or during 
cruise.
    In light of that information, the FAA determined that certain 
inspections and functional tests of the thrust reverser control and 
indication system on all Model 747 series airplanes, similar to those 
required previously for Model 757 and 767 series airplanes, are 
necessary as precautionary actions to provide an acceptable level of 
safety for Model 747 series airplanes. Subsequently, on July 13, 1994, 
the FAA issued AD 94-15-05, amendment 39-8976 (59 FR 37655, July 25, 
1994), to require inspections and functional tests of the thrust 
reverser control and indication system on all Model 747-400 series 
airplanes.
    In the preamble to the notice of AD 94-15-05, the FAA indicated 
that it was considering similar rulemaking action for other Model 747 
series airplanes. The FAA now has determined that such rulemaking 
action is indeed necessary, and this proposed AD follows from that 
determination. The FAA has determined that inspections and functional 
tests of the thrust reverser control and indication system, similar to 
those currently required by AD 94-15-05 for Model 747-400 series 
airplanes, are necessary for Model 747 SP, SR, -100, -200, and -300 
series airplanes in order to reduce the exposure of these airplanes to 
potential undetected single failures in the thrust reverser control 
system. The presence of an undetected failure in the thrust reverser 
control system, in some cases, can increase the likelihood of an 
uncommanded thrust reverser deployment in the event of an additional 
thrust reverser control system failure.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-78A2131, dated September 15, 1994, which describes procedures for 
repetitive operational tests of the reversible gearbox pneumatic drive 
unit (PDU) or the reversing air motor PDU to ensure that the unit can 
restrain the thrust reverser sleeve, and correction of any discrepancy 
found. The alert service bulletin recommends that these initial tests 
be accomplished no later than 1,300 flight hours after release of the 
alert service bulletin. The alert service bulletin also recommends a 
repetitive test interval of 2,000 flight hours.
    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 repetitive operational tests of the 
reversible gearbox pneumatic drive unit (PDU) or the reversing air 
motor PDU to ensure that the unit can restrain the thrust reverser 
sleeve, and correction of any discrepancy found during the test. The 
actions would be required to be accomplished in accordance with the 
[[Page 16394]] alert service bulletin described previously.
    In developing appropriate compliance times for the initial test 
contained in this proposed AD, the FAA considered the safety 
implications and normal maintenance schedules for timely accomplishment 
of the proposed actions. In consideration of these items, the FAA 
determined that 90 days (for the initial test of the PDU) represents 
the maximum interval of time allowable wherein that test can reasonably 
be accomplished and an acceptable level of safety can be maintained. 
Further, the FAA has determined that the proposed repetitive interval 
of 2,000 flight hours is appropriate, based on the service history of 
similar components and on an analysis of the system design to predict 
the reliability of the system during the service life of the aircraft.
    The thrust reverser control and indication system on Model 747-400 
series airplanes is similar to the system installed on the airplanes 
addressed in this proposed AD. The compliance time for the initial test 
proposed in this AD corresponds to that specified in AD 94-15-05 for 
Model 747-400 series airplanes. The repetitive test interval specified 
in this proposed AD should allow operators to perform the test during 
regularly scheduled maintenance.
    This proposed AD also would require that operators submit a report 
of initial test results to the FAA.
    This AD is considered to be interim action until final action is 
identified, at which time the FAA may consider additional rulemaking.
    As a result of recent communications with the Air Transport 
Association (ATA) of America, the FAA has learned that, in general, 
some operators may misunderstand the legal effect of AD's on airplanes 
that are identified in the applicability provision of the AD, but that 
have been altered or repaired in the area addressed by the AD. The FAA 
points out that all airplanes identified in the applicability provision 
of an AD are legally subject to the AD. If an airplane has been altered 
or repaired in the affected area in such a way as to affect compliance 
with the AD, the owner or operator is required to obtain FAA approval 
for an alternative method of compliance with the AD, in accordance with 
the paragraph of each AD that provides for such approvals. A note has 
been included in this notice to clarify this long-standing requirement.
    There are approximately 456 Model 747 SP, SR, -100, -200, and -300 
series airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 173 airplanes of U.S. registry would be affected by this 
proposed AD, that it would take approximately 16 work hours per 
airplane to accomplish the proposed actions, and that the average labor 
rate is $60 per work hour. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be 
$166,080, or $960 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 
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. 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 95-NM-06-AD.

    Applicability: Model 747 SP, SR, -100, -200, and -300 series 
airplanes equipped with Pratt & Whitney Model JT9D series engines 
(excluding Model JT9D-70 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 use the authority 
provided in paragraph (d) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition; or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To ensure the integrity of the fail safe features of the thrust 
reverser system, accomplish the following:
    (a) Within 90 days after the effective date of this AD, perform 
an operational test of the reversible gearbox pneumatic drive unit 
(PDU) or the reversing air motor PDU to ensure that the unit can 
restrain the thrust reverser sleeve, in accordance with Boeing Alert 
Service Bulletin 747-78A2131, dated September 15, 1994. Repeat the 
test thereafter at intervals not to exceed 2,000 flight hours.
    (b) If any of the tests required by this AD cannot be 
successfully performed, or if any discrepancy is found during those 
tests, accomplish either paragraph (b)(1) or (b)(2) of this AD.
    (1) Prior to further flight, correct the discrepancy found, in 
accordance with Boeing Alert Service Bulletin 747-78A2131, dated 
September 15, 1994. Or
    (2) The airplane may be operated in accordance with the 
provisions and limitations specified in an operator's FAA-approved 
Minimum Equipment List (MEL), provided that no more than one thrust 
reverser on the airplane is inoperative.
    (c) Within 30 days after performing each initial test required 
by this AD, submit a report of the test results, both positive and 
negative, to the FAA, Seattle Aircraft Certification Office (ACO), 
ANM-100S, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax 
(206) 227-1181. 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.
    (d) An alternative method of compliance or adjustment of the 
compliance time that [[Page 16395]] 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (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 May 24, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-7781 Filed 3-29-95; 8:45 am]
BILLING CODE 4910-13-U