[Federal Register Volume 64, Number 248 (Tuesday, December 28, 1999)]
[Proposed Rules]
[Pages 72579-72582]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-33569]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-66-AD]
RIN 2120-AA64


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 installation of a 
modification of the thrust reverser control and indication system and 
wiring on each engine; and repetitive functional tests of that 
installation to detect discrepancies, and repair, if necessary. This 
proposal is prompted by the results of a safety review, which revealed 
that in-flight deployment of a thrust reverser could result in a 
significant reduction in airplane controllability. 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, which could result in inadvertent deployment of 
a thrust reverser during flight, and consequent reduced controllability 
of the airplane.

DATES: Comments must be received by February 11, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-66-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: Dorr Anderson, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2684; 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-66-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-66-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On May 26, 1991, a Boeing Model 767-300ER series airplane was 
involved in an accident as a result of an uncommanded in-flight 
deployment of a thrust reverser. Following that accident, a study was 
conducted to evaluate the potential effects of an uncommanded thrust 
reverser deployment throughout the flight regime of the Boeing Model

[[Page 72580]]

747 series airplane. The study included a re-evaluation of the thrust 
reverser control system fault analysis and airplane controllability. 
The results of the evaluation indicated that, in the event of thrust 
reverser deployment during high-speed climb using high engine power, 
these airplanes also could experience control problems. This condition, 
if not corrected, could result in possible failure modes in the thrust 
reverser control system, inadvertent deployment of a thrust reverser 
during flight, and consequent reduced controllability of the airplane.
    The FAA has prioritized the issuance of AD's for corrective actions 
for the thrust reverser system on Boeing airplane models following the 
1991 accident. Based on service experience, analyses, and flight 
simulator studies, it was determined that an in-flight deployment of a 
thrust reverser has more effect on controllability of twin-engine 
airplane models than of Model 747 series airplanes, which have four 
engines. For this reason, the highest priority was given to rulemaking 
that required corrective actions for the twin-engine airplane models. 
AD's correcting the same type of unsafe condition addressed by this AD 
have been previously issued for specific airplanes within the Boeing 
Model 737, 757 and 767 series.
    Service experience has shown that in-flight thrust reverser 
deployments have occurred on Model 747 airplanes during certain flight 
conditions with no significant airplane controllability problems being 
reported. However, the manufacturer has been unable to establish that 
acceptable airplane controllability would be achieved following these 
deployments throughout the operating envelope of the airplane. 
Additionally, safety analyses performed by the manufacturer and 
reviewed by the FAA, has been unable to establish that the risks for 
uncommanded thrust reverser deployment during critical flight 
conditions is acceptably low.

Other Relevant Rulemaking

    This proposed AD is related to AD 94-15-05, amendment 39-8976 (59 
FR 37655, July 25, 1994), which is applicable to all Boeing Model 747-
400 series airplanes, and requires various inspections and tests of the 
thrust reverser control and indication system, and correction of any 
discrepancy found. Accomplishment of the actions proposed in this AD 
would terminate certain inspections and tests required by AD 94-15-05.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the following Boeing Service 
Bulletins:
     747-78-2155, Revision 2, dated November 5, 1998, which 
describes procedures for installation of an additional locking system 
on the thrust reversers;
     747-45-2016, Revision 1, dated May 2, 1996, which 
describes procedures for modifications to the central maintenance 
computer system hardware and software;
     747-31-2245, dated June 27, 1996, which describes 
procedures for modifications of the integrated display system software; 
and
     747-78-2154, Revision 3, dated December 11, 1997, which 
describes procedures for the installation of provisional wiring for an 
additional thrust reverser locking device. This service bulletin 
references the Boeing Standard Wiring Practices Manual, which describes 
wire installation and separation procedures.
    Accomplishment of Boeing Service Bulletin 747-78-2155, Revision 2, 
requires prior or concurrent accomplishment of Boeing Service Bulletins 
747-45-2016, Revision 1, 747-31-2245; and 747-78-2154, Revision 3. 
Accomplishment of these actions would eliminate the need for certain 
repetitive inspections and tests.
    The modification procedures described by Boeing Service Bulletins 
747-78-2154 and 747-78-2155 were previously validated by the 
manufacturer, and the necessary changes have been incorporated into the 
latest revisions of the service bulletins. The FAA has determined that 
the procedures specified in Boeing Service Bulletins 747-78-2154, 
Revision 3, and 747-78-2155, Revision 2, as well as the other service 
bulletins referenced in this proposed AD, have been effectively 
validated and therefore proposes that this modification be required. 
Several airplanes have been successfully modified in accordance with 
the service bulletins, and this past experience should minimize the 
likelihood for subsequent service bulletin revisions, requests for 
alternative methods of compliance, and superseding AD's.

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, this 
proposed AD would require installation of a modification of the thrust 
reverser control and indication system and wiring on each engine; and 
repetitive functional tests of that installation to detect 
discrepancies, and repair, if necessary. The actions would be required 
to be accomplished in accordance with the service bulletins described 
previously, except as discussed below.
    Repetitive functional tests to detect discrepancies of the 
actuation system lock on each thrust reverser would be required to be 
accomplished in accordance with the procedure included in Appendix 1 of 
this AD. Correction of any discrepancy detected would be required to be 
accomplished in accordance with the procedures described in the Boeing 
747 Airplane Maintenance Manual.

Differences Between Service Bulletin and This Proposed AD

    Operators should note that, although Boeing Service Bulletin 747-
78-2155, Revision 2, does not recommend a specific compliance time for 
accomplishment of the actuation system lock installation, the FAA has 
determined that an unspecified compliance time would not 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 
installation. In light of all of these factors, the FAA finds a 36-
month compliance time for completing the required actions to be 
warranted, in that it represents an appropriate interval of time 
allowable for affected airplanes to continue to operate without 
compromising safety.
    Operators also should note that, although the service bulletin does 
not specify functional testing of the actuation system lock 
installation following accomplishment of that installation, the FAA has 
determined that repetitive functional tests of the actuation system 
lock on each thrust reverser will support continued operational safety 
of thrust reversers with actuation system locks.

Cost Impact

    There are approximately 177 Model 747-400 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 53 
airplanes of U.S. registry would be affected by this proposed AD.
    For airplanes identified in Boeing Service Bulletin 747-78-2155, 
Revision 2, (45 airplanes) it would take approximately 510 work hours 
per

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airplane, to accomplish the proposed installation, at an average labor 
rate of $60 per work hour. Required parts would be provided by the 
manufacturer at no cost to the operators. Based on these figures, the 
cost impact of the installation proposed by this AD on U.S. operators 
is estimated to be $1,377,000, or $30,600 per airplane.
    For all airplanes (53 airplanes) it would take approximately 2 work 
hours per airplane, to accomplish the proposed functional test, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the functional test proposed by this AD on U.S. 
operators is estimated to be $6,360, or $120 per airplane, per test 
cycle.
    The cost impact figures discussed below refer to actions in other 
service bulletins for the airplanes identified in Boeing Service 
Bulletin 747-78-2155, Revision 2 (affects 45 U.S.-registered 
airplanes), that must be accomplished prior to or concurrent with the 
installation specified in Boeing Service Bulletin 747-78-2155, Revision 
2.
    It would take approximately 3 work hours per airplane to accomplish 
the central maintenance computer system modification, at an average 
labor rate of $60 per work hour. Required parts would be provided by 
the manufacturer at no cost to the operators. Based on these figures, 
the cost impact of the modification is estimated to be $8,100, or $180 
per airplane.
    It would take approximately 2 work hours per airplane to accomplish 
the changes to the integrated display system, at an average labor rate 
of $60 per work hour. Required parts would be provided by the 
manufacturer at no cost to the operators. Based on these figures, the 
cost impact of the modification is estimated to be $5,400, or $120 per 
airplane.
    It would take approximately 346 work hours per airplane to 
accomplish wiring provisions for the thrust reverser sync locks, at an 
average labor rate of $60 per work hour. Required parts would be 
provided by the manufacturer at no cost to the operators. Based on 
these figures, the cost impact of the modification is estimated to be 
$934,200, or $20,760 per airplane.
    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-66-AD.

    Applicability: Model 747-400 series airplanes equipped with 
Pratt & Whitney PW4000 series 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 (c) 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 inadvertent deployment of a thrust reverser during 
flight and consequent reduced controllability of the airplane, 
accomplish the following:

Modifications

    (a) For airplanes identified in Boeing Service Bulletin 747-78-
2155, Revision 2, dated November 5, 1998: Accomplish the 
requirements of paragraphs (a)(1) and (a)(2) of this AD at the times 
specified in those paragraphs. Accomplishment of these actions 
constitutes terminating action for the inspections and tests 
required by paragraph (a) of AD 94-15-05, amendment 39-8976.
    (1) Within 36 months after the effective date of this AD: 
Install an additional locking system on each engine thrust reverser 
in accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 747-78-2155, Revision 2, dated November 5, 1998.
    (2) Prior to or concurrent with the installation required by 
paragraph (a)(1) of this AD, accomplish the requirements of 
paragraphs (a)(2)(i), (a)(2)(ii), and (a)(2)(iii) of this AD:
    (i) Modify the central maintenance computer system hardware and 
software in accordance with Boeing Service Bulletin 747-45-2016, 
Revision 1, dated May 2, 1996.
    (ii) Modify the integrated display system software in accordance 
with Boeing Service Bulletin 747-31-2245, dated June 27, 1996.
    (iii) Install the provisional wiring for the locking system on 
the thrust reversers in accordance with Boeing Service Bulletin 747-
78-2154, Revision 3, dated December 11, 1997.

Repetitive Functional Tests

    (b) Within 4,000 hours time-in-service after accomplishment of 
paragraph (a) of this AD, or production equivalent; or within 1,000 
hours time-in-service after the effective date of this AD, whichever 
occurs later: Perform a functional test to detect discrepancies of 
the additional locking system on each engine thrust reverser, in 
accordance with Appendix 1 of this AD. Prior to further flight, 
correct any discrepancy detected and repeat the functional test of 
that repair, in accordance with the procedures described in the 
Boeing 747 Airplane Maintenance Manual. Repeat the functional test 
thereafter at intervals not to exceed 4,000 hours time-in-service.

Alternative Methods of Compliance

    (c) 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

[[Page 72582]]

Special Flight Permit

    (d) 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.

Appendix 1--Thrust Reverse Sync-Lock--Adjustment/Test

    1. General.
    A. There are two sync-locks for each engine thrust reverser. The 
sync-lock is installed on the lower non-locking hydraulic actuator 
of each thrust reverser sleeve.
    B. The Thrust Reverser Sync-Lock Integrity Test has two tasks:
    (1) The first task does a test of the electrical circuit which 
controls the operation of the sync-lock on each thrust reverser 
sleeve.
    (2) The second task does a test of the mechanical function of 
the sync-lock on each thrust reverser sleeve.
    C. The thrust reverser sync-lock is referred to as ``the sync-
lock'' in this procedure.
    2. Thrust Reverser Sync-Lock Integrity Test.
    A. Equipment--Multi-meter, Simpson 260 or equivalent--
commercially available
    B. Prepare to do the integrity test for the sync-locks
    (1) Supply electrical power
    (2) For the applicable engine, make sure these circuit breakers 
on the Main Power Distribution Panel P6, are closed:

6F12 ENG 1 T/R IND
6E12 ENG 2 T/R IND
6D12 ENG 3 T/R IND
6C12 ENG 4 T/R IND
6F13 ENG 1 T/R CONT
6E13 ENG 2 T/R CONT
6D13 ENG 3 T/R CONT
6C13 ENG 4 T/R CONT
6F11 ENG 1 T/R LOCK CONT
6E11 ENG 2 T/R LOCK CONT
6D11 ENG 3 T/R LOCK CONT
6C11 ENG 4 T/R LOCK CONT

    (3) Open the fan cowl panels for the applicable engine.
    C. Do the electrical integrity test for the sync-locks.
    (1) Do these steps, for the applicable engine, to make sure 
there are no ``hot'' short circuits in the electrical system which 
can accidentally supply power to the sync-locks:
    (a) Remove the electrical connector, D20194, from the sync-lock, 
V170, on the left sleeve of the thrust reverser.
    (b) Remove the electrical connector, D20196, from the sync-lock, 
V171, on the right sleeve of the thrust reverser.
    (c) Use a multi-meter on the plug end of the applicable 
electrical connector to make sure that these conditions are correct:

D20194 PIN 1  D20194 PIN 2  -3 to +1 VDC and continuity (less than 5 
ohms)
D20196 PIN 1  D20196 PIN 2  -3 to +1 VDC and continuity (than 5 
ohms)

    (d) If you find the correct conditions, do the mechanical 
integrity test for the sync-locks.
    (e) If you did not find these conditions to be correct, you must 
do these steps:
    (1) Make a careful visual inspection of all the electrical wires 
and connectors between the sync-lock and its power circuit.
    (2) Repair all the unserviceable electrical wire and connectors 
that you find.
    (3) Use the multi-meter again to make sure there are no ``hot'' 
short circuits in the electrical system which can accidentally 
supply power to the sync-locks.
    D. Do the mechanical integrity test for the sync-locks.
    (1) Supply hydraulic power.
    WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE CLEAR OF THE 
AREA BEHIND EACH THRUST REVERSER. IF YOU DO NOT OBEY THIS 
INSTRUCTION, INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR IF 
THE SYNC-LOCKS DO NOT OPERATE CORRECTLY AND THE THRUST REVERSER 
EXTENDS.
    (2) Move the applicable reverser thrust lever aft to try to 
extend the thrust reverser with hydraulic power.

    Note: If the thrust reverser sleeves do not extend, the sync-
locks are serviceable. If the thrust reverser sleeves extend, the 
applicable sync-lock did not operate correctly.

    (3) Replace the sync-lock(s) on the thrust reverser sleeve(s) 
that did extend when you moved the reverse thrust levers. Repeat 
steps 2.D.(1) and 2.D.(2) to verify that functional sync-locks are 
installed.
    (4) Move the applicable thrust reverser lever forward to the 
stow position.
    (5) Install the electrical connector, D20194, on the sync-lock, 
V170 on the left sleeve of the thrust reverser.
    (6) Install the electrical connector, D20196, on the sync-lock, 
V171, on the right sleeve of the thrust reverser.
    WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE CLEAR OF THE 
AREA BEHIND EACH THRUST REVERSER. IF YOU DO NOT OBEY THIS 
INSTRUCTION, INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR 
WHEN THE THRUST REVERSERS ARE EXTENDED.
    (7) Move the applicable thrust reverser aft to try to extend the 
thrust reverser with hydraulic power.

    Note: If the thrust reverser sleeves extended, the sync-locks 
are serviceable. If the thrust reverser sleeves did not extend, the 
applicable sync-lock is not serviceable.

    (8) Replace the sync-lock(s) on the thrust reverser sleeve that 
did not extend when you moved the reverse thrust levers. Repeat 
steps 2.D.(4) through 2.D.(7) to verify that functional sync-locks 
are installed.
    (9) Repeat steps 2.A. through 2.D. for all other engine 
positions.
    E. Put the airplane back to its usual condition.
    (1) Move the reverse thrust levers forward to fully retract the 
thrust reversers on the applicable engine.
    (2) Remove the hydraulic power if it is not necessary.
    (3) Remove the electrical power if it is not necessary.
    (4) Close the fan cowl panels.

    Issued in Renton, Washington, on December 21, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-33569 Filed 12-27-99; 8:45 am]
BILLING CODE 4910-13-U