Airworthiness Directive · Amendment 39-11741 · Boeing Model 747 Series Airplanes Equipped With Pratt & Whitney JT9D-70 Series Engines
Boeing Model 747 Series Airplanes Equipped With Pratt & Whitney JT9D-70 Series Engines
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.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires inspections, tests, and certain modifications of the thrust reverser control and indication system and wiring on each engine, and corrective action, if necessary. This amendment also requires installation of a terminating modification, and repetitive functional tests of that installation to detect discrepancies, and repair, if necessary. This amendment 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 this 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.
To prevent inadvertent deployment of a thrust reverser during flight and consequent reduced controllability of the airplane, accomplish the following:
(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.
(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.
(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.
(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.
(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.
(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.
