[Federal Register Volume 60, Number 138 (Wednesday, July 19, 1995)]
[Rules and Regulations]
[Pages 36974-36976]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-17709]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-122-AD; Amendment 39-9314; AD 94-21-05 R1]


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series Airplanes Equipped With CFM International CFM56-3 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; correction.

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SUMMARY: This amendment clarifies an existing airworthiness directive 
(AD), applicable to certain Boeing Model 737-300, -400, and -500 series 
airplanes, that currently requires modification, adjustments, and tests 
of the thrust reverser system; and repair, if necessary. This amendment 
clarifies a requirement specified in the AD concerning the performance 
of the operational test of the system. This amendment is prompted by an 
inquiry from an operator of the affected airplanes concerning that 
aspect of the existing AD.

DATES: Effective November 25, 1994. -
    The incorporation by reference of certain publications listed in 
the regulations was approved by the Director of the Federal Register as 
of November 25, 1994 (59 FR 53573, October 25, 1994).

ADDRESSES: The service information referenced in this AD 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; or at the Office of the Federal Register, 800 North Capitol 
Street NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Stephen Bray, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-
2681; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: On October 6, 1994, the FAA issued AD 94-21-
05, amendment 39-9047 (59 FR 53573, October 25, 1994), applicable to 
certain Boeing Model 737-300, -400, and -500 series airplanes, to 
require modification, adjustments, and tests of the thrust reverser 
system; and repair, if necessary. The actions required by that AD are 
intended to prevent deployment of a thrust reverser in flight and 
subsequent reduced controllability of the airplane. -
    Since the issuance of that AD, the FAA has received an inquiry from 
an operator of the affected airplanes concerning the requirement of 
paragraph (d)(2) of the AD. That paragraph requires deactivation of a 
thrust reverser if a discrepancy is found during accomplishment of the 
thrust reverser sync-lock integrity test. The last sentence of 
paragraph (d)(2) specifies that, following deactivation of the 
associated thrust reverser, ``the sync-locks installed on the 
deactivated thrust reverser must remain operational.'' The operator 
questions how the sync-lock can remain ``operational'' when the thrust 
reverser has been deactivated for failing the required integrity test. 
-
    The FAA finds that clarification of the term ``operational'' is 
necessary. The FAA's intent in specifying that the sync-lock remain 
operational was actually to require that it be verified to be in the 
locked position. In order to avoid unnecessary flight delays and 
cancellations, the FAA included the provision contained in paragraph 
(d)(2) of AD 94-21-05 to provide relief to allow dispatch of the 
airplane with deactivated sync-locks, in accordance with provisions and 
limitations contained in the Master Minimum Equipment List (MMEL). This 
relief involves locking out a thrust reverser and verifying that the 
failed sync-lock is deactivated and in the locked position. In light of 
this, action is taken herein to revise AD 94-21-05 to clarify paragraph 
(d)(2) of the AD accordingly. There are no other changes to the rule. -
    The final rule is being reprinted in its entirety for the 
convenience of affected operators. The effective date remains November 
25, 1994. -
    Since this action only clarifies a requirement of a final rule, it 
has no adverse economic impact and imposes no additional burden on any 
person. Therefore, notice and public procedures hereon are unnecessary.

List of Subjects in 14 CFR Part 39 -

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment -

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation 

[[Page 36975]]
Administration amends 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 removing amendment 39-9047 (59 FR 
53573, October 25, 1994), and by adding a new airworthiness directive 
(AD), amendment 39-9314, to read as follows:

94-21-05 R1 Boeing: Amendment 39-9314. Docket 93-NM-122-AD. Revises 
AD 94-21-05, Amendment 39-9047.

    -Applicability: Model 737-300, -400, and -500 series airplanes 
equipped with CFM International CFM56-3 series engines, certificated 
in any category. -
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent deployment of a thrust reverser in flight and 
subsequent reduced controllability of the airplane, accomplish the 
following:
    (a) For airplanes on which the sync-lock installation [specified 
in paragraph (b) of this AD], sync-lock wiring modification 
[specified in paragraph (c) of this AD], or Production Revision 
Record (PRR) 35105 has not been accomplished: Within 60 days after 
the effective date of this AD, and thereafter at intervals not to 
exceed 4,000 hours time-in-service, perform adjustments and tests of 
the thrust reverser system that are specified in Section 78-31-00 of 
the Boeing 737 Maintenance Manual to verify proper operation of the 
thrust reverser system, in accordance with that section of the 
maintenance manual. If any discrepancy is found, prior to further 
flight, accomplish either paragraph (a)(1) or (a)(2) of this AD.
    (1) Repair any discrepancy found, in accordance with procedures 
described in the Boeing 737 Maintenance Manual. Or
    (2) Deactivate the associated thrust reverser in accordance with 
the existing provisions and limitations specified in the Master 
Minimum Equipment List (MMEL).
    (b) For airplanes on which the sync-lock feature was not 
installed during production or as a modification in accordance with 
Boeing Service Bulletin 737-78-1053, dated December 17, 1992: Within 
5 years after the effective date of this AD, install an additional 
thrust reverser system locking feature (sync-lock installation) in 
accordance with Boeing Service Bulletin 737-78-1053, Revision 1, 
dated July 1, 1993; Revision 2, dated February 17, 1994; or Revision 
3, dated June 30, 1994. Installation of the additional locking 
feature constitutes terminating action for the tests required by 
paragraph (a) of this AD.
    (c) For airplanes listed in Boeing Service Bulletin 737-78-1058, 
dated July 1, 1993: Within 5 years after the effective date of this 
AD, modify the sync-lock wiring in accordance with Boeing Service 
Bulletin 737-78-1058, dated July 1, 1993; Revision 1, dated February 
17, 1994; or Revision 2, dated July 7, 1994. Modification of the 
sync-lock wiring constitutes terminating action for the tests 
required by paragraph (a) of this AD.
    (d) At the times specified in paragraph (e) of this AD, 
accomplish the ``Thrust Reverser Sync-Lock Integrity Test'' 
specified below to verify that the sync-locks are not failing in the 
unlocked state. If any discrepancy is found, prior to further 
flight, accomplish paragraph (d)(1) or (d)(2) of this AD.
    (1) Repair any discrepancy found, in accordance with procedures 
specified in the Boeing 737 Maintenance Manual. Or
    (2) Deactivate the associated thrust reverser in accordance with 
the existing provisions and limitations specified in the MMEL; and 
verify that the failed sync-lock is deactivated and in the locked 
position.

``THRUST REVERSER SYNC-LOCK INTEGRITY TEST

1. General

A. Use this procedure to test the integrity of the thrust reverser 
sync-locks. -
    The procedure must be performed on each engine.

2. Thrust Reverser Sync-Lock Test

A. Prepare for the Thrust Reverser Sync-Lock test.
    (1) Do the steps that follow to supply power to the thrust 
reverser -system:
    (a) Make sure the thrust levers are in the idle position.
    (b) Make sure the thrust reversers are retracted and locked.
    (c) Make sure these circuit breakers on the P6 circuit breaker 
panel are closed:
    (1) ENGINE 1 THRUST REVERSER CONT SYS
    (2) ENGINE 2 THRUST REVERSER CONT SYS
    (3) ENGINE 2 THRUST REVERSER CONT -SYS-ALT
    (4) ENGINE 1 THRUST REVERSER IND SYS
    (5) ENGINE 2 THRUST REVERSER IND SYS
    (6) ENGINE 1 SYNC-LOCK
    (7) ENGINE 2 SYNC-LOCK
    (8) ENGINE 2 SYNC-LOCK-ALTN
    (9) LANDING GEAR AIR/GND RELAY AND LIGHTS
    (10) RADIO ALTM-2
    (d) Make sure this circuit breaker on the P18 circuit breaker 
panel is closed:
    (1) RADIO ALTM-1
    (e) Supply electrical power.
    (f) Remove pressure from the A (for the left engine) or B (for 
the right engine) hydraulic system.
B. Do the thrust reverser sync-lock test.
    (1) Move and hold the manual unlock lever on the upper actuator 
on -both thrust reverser sleeves to the unlock position.
    (2) Make sure the thrust reverser sleeves did not move aft.
    (3) Move the left (right) reverse thrust lever up and rearward 
to the -reverse thrust position.
    (4) Make sure both thrust reverser sleeves move aft 
(approximately -0.15 to 0.25 inch).
    (5) Release the manual unlock lever on the upper actuators.
    WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE CLEAR OF THE 
AREA AROUND THE THRUST REVERSER. WHEN YOU APPLY HYDRAULIC PRESSURE, 
THE THRUST REVERSER WILL EXTEND AND CAN CAUSE INJURIES TO PERSONS OR 
DAMAGE TO EQUIPMENT.

    (6) Pressurize the A (B) hydraulic system.
    (7) Make sure the thrust reverser extends.
    (8) Move the left (right) reverse thrust lever to the forward 
and down -position to retract the thrust reverser.
C. Put the airplane back to its usual condition.
    (1) Remove hydraulic pressure.
    (2) Remove electrical power.
D. Repeat the thrust reverser sync-lock test on the other engine.''

    (e) Accomplish the test required by paragraph (d) of this AD at 
the times specified in paragraph (e)(1) or (e)(2) of this AD, as 
applicable.
    (1) For airplanes that are subject to the requirements of 
paragraphs (b) and (c) of this AD: Within 4,000 hours time-in-
service after accomplishing the modification required by paragraph 
(b) or (c) of this AD, as applicable, or within 4,000 hours time-in-
service after the effective date of this AD, whichever occurs later; 
and thereafter at intervals not to exceed 4,000 hours time-in-
service.
    (2) For all other airplanes: Within 4,000 total hours time-in-
service, or within 4,000 hours time-in-service after the effective 
date of this AD, whichever occurs later; and thereafter at intervals 
not to exceed 4,000 hours time-in-service.
    (f) 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.
    (g) 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.
    (h) The installation and wiring modification shall be done in 
accordance with Boeing Service Bulletin 737-78-1053, Revision 1, 
dated July 1, 1993; Boeing Service Bulletin 737-78-1053, Revision 2, 
dated February 17, 1994; Boeing Service Bulletin 737-78-1053, 
Revision 3, dated June 30, 1994; Boeing Service Bulletin 737-78-
1058, dated July 1, 1993; Boeing Service Bulletin 737-78-1058, 
Revision 1, dated February 17, 1994; or Boeing Service Bulletin 737-
78-1058, Revision 2, dated July 7, 1994. The incorporation by 
reference of this document was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51 as of November 25, 1994 (59 FR 53573, October 

[[Page 36976]]
25, 1994). Copies may be obtained from Boeing Commercial Airplane 
Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street NW., suite 700, Washington, DC.

    (i) This amendment is effective on November 25, 1994.

    Issued in Renton, Washington, on July 13, 1995.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-17709 Filed 7-18-95; 8:45 am]
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