Airworthiness Directive · Amendment 39-11551 · Boeing Model 747-400 Series Airplanes Equipped With General Electric CF6-80C2 Series Engines
Boeing Model 747-400 Series Airplanes Equipped With General Electric CF6-80C2 Series Engines
Superseded. A later AD replaced this one: AD 2000-09-03. Comply with the one in force.
Model 747-400 series airplanes equipped with General Electric CF6-80C2 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 (d)(1) 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.
This amendment adopts a new airworthiness directive (AD) applicable to certain Boeing Model 747-400 series airplanes that requires various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. This amendment is prompted by reports indicating that several center drive units (CDU) were returned to the manufacturer of the CDU's because of low holding torque of the CDU cone brake. The actions specified by this 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.
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, accomplish the following:
(a) Within 1,000 hours time-in-service after the most recent test of the center drive unit (CDU) cone brake performed in accordance with paragraph (b)(1) of AD 94-15-05, amendment 39-8976; or within 650 hours time-in-service after the effective date of this AD, whichever occurs first: Perform a functional test to detect discrepancies of the CDU cone brake on each thrust reverser, in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; or the applicable section of paragraph III.A. of the Accomplishment Instructions of Boeing Service Bulletin 747-78A2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997.
Note 2: Accomplishment of the CDU cone brake test during production in accordance with Production Revision Record (PRR) 80452-102 prior to the effective date of this AD is considered acceptable for compliance with the test required by paragraph (a) of this AD.
(1) For Model 747-400 series airplanes equipped with thrust reversers that have not been modified in accordance with Boeing Service Bulletin 747-78-2151 or a production equivalent: Repeat the functional test of the CDU cone brake thereafter at intervals not to exceed 650 hours time-in-service.
(2) For Model 747-400 series airplanes equipped with thrust reversers that have been modified in accordance with Boeing Service Bulletin 747-78-2151 or a production equivalent: Repeat the functional test of the CDU cone brake thereafter at intervals not to exceed 1,000 hours time-in-service.
Note 3: Model 747-400 series airplanes, line numbers 1061 and subsequent, equipped with GE CF6-80C2 engines, had a third locking system installed during production in accordance with Production Revision Record (PRR) 80452-102, and were not modified in accordance with Boeing Service Bulletin 747-78-2151 (which is a retrofit action for airplanes having line numbers 700 through 1060 inclusive).
(b) Accomplishment of the functional test of the CDU cone brake, as specified in paragraph (a) of this AD, constitutes terminating action for the repetitive tests of the CDU cone brake required by paragraph (b)(1) of AD 94-15-05.
(c) If any functional test required by paragraph (a) of this AD cannot be successfully performed as specified in the referenced service bulletin, or if any discrepancy is detected during any functional test required by paragraph (a) of this AD, accomplish either paragraph (c)(1) or (c)(2) of this AD.
(1) Prior to further flight, repair in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; or Boeing Service Bulletin 747-78A2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997, Or,
(2) The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved MEL, provided that no more than one thrust reverser on the airplane is inoperative.
(d)(1) 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.
(2) Alternative methods of compliance for the functional test of the Thrust Reverser Actuation System (TRAS) lock for Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines that have been modified in accordance with Boeing Service Bulletin 747-78-2151, or production equivalent, approved previously in accordance with AD 94-15-05, amendment 39-8976, are considered to be approved as alternative methods of compliance with this AD.
Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
