[Federal Register Volume 65, Number 24 (Friday, February 4, 2000)]
[Proposed Rules]
[Pages 5459-5465]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-2415]



[[Page 5459]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-65-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes 
Equipped With Pratt & Whitney JT9D-70 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 series 
airplanes. This proposal would require inspections, tests, and certain 
modifications of the thrust reverser control and indication system and 
wiring on each engine, and corrective action, if necessary.
    This proposal also would require installation of a terminating 
modification, 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 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 March 20, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-65-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: Larry Reising, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2683; 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-65-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-65-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 
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.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the following Boeing Service 
Bulletins:
     747-78A2159, dated May 18, 1995, which describes 
procedures for repetitive inspections and tests of the thrust reverser 
control and indication system to detect discrepancies, and corrective 
action, if necessary. The corrective action includes, among other 
things, repair or replacement of any discrepant parts with new parts.
     747-78-2153, Revision 1, dated November 27, 1996, which 
describes procedures for installation of an additional locking system 
on the thrust reversers. This service bulletin references the following 
service bulletins:

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    1. Boeing Service Bulletin 747-78-2135, dated August 31, 1995, 
which describes procedures for the installation of provisional wiring 
for an additional thrust reverser locking device.
    2. Boeing Service Bulletin 747-78A2149, Revision 1, dated May 9, 
1996, and Revision 2, dated August 29, 1996, which describe procedures 
for inspection of the thrust reverser control system wiring to detect 
damaged wires; modification of certain wiring, and an operational test 
of the thrust reverser. This service bulletin references Boeing 
Standard Wiring Practices Manual, which describes procedures for repair 
or replacement of certain wire bundles, if necessary.
    3. Rohr Service Bulletin TBC-CNS 78-33, Revision 1, dated August 
20, 1996, which describes additional procedures for installation of an 
additional locking system on the thrust reversers.
    Accomplishment of Boeing Service Bulletin 747-78-2153, Revision 1, 
requires prior or concurrent accomplishment of Boeing Service Bulletins 
747-78-2135 and 747-78A2149, Revision 1 or Revision 2; and concurrent 
accomplishment of Rohr Service Bulletin TBC-CNS 78-33, Revision 1. 
Accomplishment of these actions would eliminate the need for certain 
repetitive inspections and tests.
    The FAA also has reviewed and approved Rohr Service Bulletin TBC-
CNS 78-32, Revision 1, dated August 20, 1996, which describes 
procedures for modification of the thrust reverser control system 
wiring concurrent with accomplishment of Boeing Service Bulletin 747-
78A2149, Revision 1 or Revision 2.
    The modification procedures described by Boeing Service Bulletins 
747-78-2153, and 747-78-2135 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 747-78-2153, 
Revision 1, and 747-78-2135, as well as the other service bulletins 
referenced in this proposed AD, have been effectively validated and 
therefore proposes that this modification be required.

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 inspection of the thrust reverser control and 
indication system and wiring on each engine, and corrective action, if 
necessary; and eventual modification of the wiring. This proposal also 
would require installation of a terminating modification 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-
78-2153, Revision 1, 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 repetitive 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 7 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 6 
airplanes of U.S. registry would be affected by this proposed AD.
    It would take approximately 32 work hours (8 work hours per engine) 
per airplane, to accomplish the proposed thrust reverser inspection, 
modification, and test, described in 747-78A2149, Revision 1, or 
Revision 2, 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 is 
estimated to be $11,520, or $1,920 per airplane.
    It would take approximately 8 work hours (2 work hours per engine) 
per airplane, to accomplish the proposed 1,000-flight-hour inspections 
described in Boeing Service Bulletin 747-78A2159, at an average labor 
rate of $60 per work hour. Based on these figures, the cost impact of 
the inspection proposed by this AD on U.S. operators is estimated to be 
$2,880, or $480 per airplane, per inspection cycle.
    It would take approximately 20 work hours (5 work hours per engine) 
per airplane, to accomplish the proposed 18-month thrust reverser 
system checks described in Boeing Service Bulletin 747-78A2159, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the test proposed by this AD on U.S. operators is 
estimated to be $7,200, or $1,200 per airplane, per test cycle.
    It would take approximately 544 work hours per airplane, to 
accomplish the proposed provisional wiring, 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 proposed AD on U.S. operators is estimated to be $195,840, or 
$32,640 per airplane.
    It would take approximately 593 work hours per airplane, to 
accomplish the proposed sync lock 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 $213,480, or $35,580 per airplane.
    It would take approximately 4 work hours per airplane, to 
accomplish the proposed functional test of the additional locking 
system, at an average labor rate of $60 per work hour. Based on these 
figures, the cost impact of the test proposed by this AD on U.S. 
operators is estimated to be $1,680, or $240 per airplane, per test 
cycle.
    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

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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-65-AD.

    Applicability: Model 747 series airplanes equipped with Pratt & 
Whitney JT9D-70 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 (g) 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:

Inspection/Repair

    (a) Within 200 flight hours or 50 flight cycles after the 
effective date of this AD, whichever occurs later: Inspect the 
thrust reverser wiring on each engine to detect discrepancies, in 
accordance with Boeing Service Bulletin 747-78A2149, Revision 1, 
dated May 9, 1996, or Revision 2, dated August 29, 1996. Prior to 
further flight, repair any discrepancy, in accordance with the 
service bulletin.

Modification and Tests

    (b) Within 5,000 flight hours or 500 flight cycles after the 
effective date of this AD, whichever occurs later: Accomplish the 
thrust reverser wiring modification on each engine in accordance 
with Boeing Service Bulletin 747-78A2149, Revision 1, dated May 9, 
1996, or Revision 2 dated August 29, 1996.
    (1) Concurrent with accomplishment of Boeing Service Bulletin 
747-78A2149, Revision 1 or Revision 2: Accomplish the modification 
of the thrust reverser control system wiring specified in Rohr 
Service Bulletin TBC-CNS 78-32, Revision 1, dated August 20, 1996.
    (2) Prior to further flight following accomplishment of the 
modification specified in paragraphs (b) and (b)(1): Perform an 
operational test of the thrust reverser wiring on each engine to 
detect discrepancies in accordance with Boeing Service Bulletin 747-
78A2149, Revision 1, dated May 9, 1996, or Revision 2 dated August 
29, 1996. Prior to further flight, correct any discrepancy detected, 
in accordance with the service bulletin.

Repetitive Inspections and Tests

    (c) Perform the inspections and tests of the thrust reverser 
control and indication system to detect discrepancies at the times 
specified in paragraphs (c)(1) and (c)(2) of this AD, in accordance 
with Boeing Alert Service Bulletin 747-78A2159, dated May 18, 1995.
    (1) Within 90 days after the effective date of this AD, inspect 
in accordance with Part III, ``1,000 Flight Hour Inspections'' of 
the Accomplishment Instructions of the alert service bulletin. 
Repeat at intervals not to exceed 1,000 flight hours until 
accomplishment of paragraph (f) of this AD.
    (2) Within 1,500 flight hours or 4 months after the effective 
date of this AD, whichever occurs later, inspect and test in 
accordance with Part III, ``18 Month Thrust Reverser System Checks'' 
of the Accomplishment Instructions of the alert service bulletin. 
Repeat at intervals not to exceed 18 months until accomplishment of 
paragraph (e) of this AD.

Corrective Actions

    (d) If any inspection or test required by paragraph (c) of this 
AD cannot be successfully performed as specified in the referenced 
service bulletin, or if any discrepancy is detected during any 
inspection or test, prior to further flight, repair in accordance 
with Boeing Alert Service Bulletin 747-78A2159, dated May 18, 1995.
    Additionally, prior to further flight, any failed inspection or 
test required by paragraph (c) of this AD must be repeated and 
successfully accomplished.

Terminating Action

    (e) Accomplish the requirements of paragraphs (e)(1) and (e)(2) 
of this AD at the times specified in those paragraphs. 
Accomplishment of these actions constitutes terminating action for 
the repetitive inspections and tests required by paragraph (c) of 
this AD.
    (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 747-78-2153, Revision 1, dated November 27, 1996.
    (2) Prior to or concurrent with accomplishment of Boeing Service 
Bulletin 747-78-2153, Revision 1: Accomplish the installation of 
provisional wiring for the locking system on the thrust reversers in 
accordance with Boeing Service Bulletins 747-78-2135, dated August 
31, 1995; and 747-78A2149, Revision 1, dated May 9, 1996, or 
Revision 2, dated August 29, 1996. Additionally, concurrent with 
accomplishment of Boeing Service Bulletin 747-78-2153, Revision 1, 
accomplish the installation of the provisional wiring described 
previously in accordance with Rohr Service Bulletin TBC-CNS 78-33, 
Revision 1, dated August 20, 1996.

Repetitive Functional Tests

    (f) Within 4,000 hours time-in-service after accomplishment of 
paragraph (e) of this AD: Perform a functional test to detect 
discrepancies of the additional locking system on each thrust 
reverser, in accordance with Appendix 1 (including Figures 1 and 2) 
of this AD. Prior to further flight, correct any discrepancy 
detected, 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

    (g) 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.


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

Special Flight Permit

    (h) 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 Reverser Sync-Lock Integrity Test

1. General

A. Equipment and Materials

(1) Thrust reverser flex drive adapter--196K8004-1 or 196K8004-3; 
Rohr Industries, Inc., Chula Vista, California 92012.

2. Thrust Reverser Sync-Lock Integrity Test

B. Prepare for the Thrust Reverser Sync Lock Test

(1) Open applicable T/R CONT & BLEED SYS circuit breaker on P12 
circuit breaker panel.
(2) Open fan cowl doors (Ref 71-11-02, Maintenance Practices).
(3) Check that forward and aft circumferential latches and all 
tension latches are engaged and locked.
(4) Depress drive unit latch operating arm and retain by engaging 
latch arm (detail C).
(5) Disengage stow latch hook on left and right thrust reversers 
(detail D).
(6) On either lower slave actuator (detail B), either remove 
coverplate from forward drive pad or remove locking plug from lower 
drive pad.
(7) Move left-hand sync-lock lever to the unlocked position.
(8) Using appropriate drive adapter (196K8004-1 at forward drive pad 
or 196K8004-3 at lower drive pad), attempt to manually deploy 
sleeves.

    CAUTION: DO NOT APPLY A TORQUE LOAD OF MORE THAN 75
    POUND-INCHES TO THE ACTUATOR; A GREATER TORQUE LOAD CAN CAUSE 
DAMAGE TO THE MECHANISM.

(9) If sleeves move, replace the right-hand sync-lock.
(10) Move left-hand sync-lock lever to the locked position.
(11) Move right-hand sync-lock lever to the unlocked position.
(12) Repeat step (8) above.
(13) If sleeves move, replace the left-hand sync-lock.
(14) Move left-hand sync-lock lever to the unlocked position.
(15) Rotate actuator gearshaft to fully stow the sleeves.
(16) When translating sleeves reach stowed position, check that stow 
latch hooks have engaged fixed hooks on both sides (detail D).
(17) Depress latch operating arm and disengage latch arm (detail C); 
allow latch arm to raise.
(18) After releasing arm, verify latch engagement by attempting to 
rotate feedback gear on drive unit using 1/4-inch square drive; gear 
shall not rotate in excess of 0.1 of a turn.

    CAUTION: DO NOT APPLY A TORQUE LOAD OF MORE THAN 25 POUND-INCHES 
ON FEEDBACK GEAR; A GREATER TORQUE LOAD CAN CAUSE DAMAGE TO THE 
MECHANISM.

(19) As applicable, install locking plug (with square section facing 
away from drive pad) or coverplate on actuator drive pad. Secure 
plug or plate with bolts tightened to 50-70 pound-inches.
(20) Move both left-and right-hand sync-lock levers to the locked 
position.
(21) Close fan cowl doors (Ref 71-11-02, Maintenance Practices).
(22) Close T/R CONT & BLEED SYS circuit breaker.
(23) Repeat the sync-lock integrity test on all remaining thrust 
reversers.

BILLING CODE 4910-13-P

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    Issued in Renton, Washington, on January 28, 2000.
Donald L. Riggin,
Acting Manager Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 00-2415 Filed 2-3-00; 8:45 am]
BILLING CODE 4910-13-C