Airworthiness Directive · Amendment 39-11821 · Boeing Model 747 Series Airplanes
Boeing Model 747 Series Airplanes
Model 747 series airplanes; certificated in any category; equipped with General Electric Model CF6-45 or -50 series engines.
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 (h) 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 equipped with General Electric Model CF6-45 or -50 series engines, that requires repetitive inspections and tests of the thrust reverser control and indication system, and corrective actions, if necessary. This amendment also requires installation of a thrust reverser actuation system (TRAS) lock, repetitive functional tests of that installation, and repair, if necessary. Installation of the TRAS lock terminates the repetitive inspections and certain tests. This amendment 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 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 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, accomplish the following:
Note 2: For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”
(a) Within 90 days after the effective date of this AD, perform the applicable detailed visual inspections and tests to verify proper operation of the thrust reverser stow/deploy switches, the bullnose seals, and the airmotor brake on each engine, in accordance with Work Package I of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable inspections and tests thereafter at intervals not to exceed 1,500 flight hours, until accomplishment of paragraph (d) of this AD.
(b) Within 6 months after the effective date of this AD, perform the applicable detailed visual inspections and tests to verify proper operation of the overpressure shutoff valve electrical connectors, the flexible shafts, the directional pilot valve, and the microswitch pack for each engine, in accordance with Work Package II of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable inspections and tests thereafter at intervals not to exceed 18 months, until accomplishment of paragraph (d) of this AD.
(c) If any of the inspections and tests required by paragraphs (a) and (b) of this AD cannot be successfully performed, or if any discrepancy is detected during the inspections and tests, accomplish paragraphs (c)(1) or (c)(2) of this AD, as applicable.
(1) Prior to further flight, repair in accordance with Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to further flight, any failed inspection or test required by paragraph (a) or (b) of this AD must be repeated and successfully accomplished.
(2) Accomplish both paragraphs (c)(2)(i) and (c)(2)(ii) of this AD.
(i) Prior to further flight, deactivate the associated thrust reverser in accordance with Section 78-1 of Boeing Document D6-33391, “Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,” Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph.
Note 3: The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved Minimum Equipment List (MEL), provided that no more than one thrust reverser on the airplane is inoperative.
(ii) Within 10 days after deactivation of any thrust reverser in accordance with paragraph (c)(2)(i) of this AD, the affected thrust reverser must be repaired in accordance with Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to further flight, any failed inspection or test required by paragraph (a) or (b) of this AD must be repeated and successfully accomplished; once such inspections and tests have been successfully accomplished, the thrust reverser may then be reactivated.
(d) Within 48 months after the effective date of this AD, install a thrust reverser actuation system (TRAS) lock on each thrust reverser half of each engine, in accordance with Boeing Service Bulletin 747-78-2150, Revision 1, dated July 2, 1998. All of the modifications described in the service bulletins listed in paragraphs I.K.1.h. and I.K.1.j. of Boeing Service Bulletin 747-78-2150, Revision 1, must be accomplished, as applicable, in accordance with those service bulletins, prior to, or concurrently with, the accomplishment of the installation of the TRAS lock. Accomplishment of these actions constitutes terminating action for the repetitive inspections required by paragraphs (a) and (b) of this AD.
Note 4: Accomplishment of the installation specified in Boeing Service Bulletin 747-78-2150, dated March 20, 1997, is acceptable for compliance with the installation required by paragraph (d) of this AD.
(e) Within 3,000 flight hours after accomplishing the modification required by paragraph (d) of this AD, or within 1,000 flight hours after the effective date of this AD, whichever occurs later, perform a functional test of the TRAS lock on each reverser half, in accordance with Chapter 78-34-00 of the Boeing 747 Maintenance Manual, dated April 25, 1998.
(1) If no discrepancy is detected, repeat the functional test thereafter at intervals not to exceed 3,000 flight hours.
(2) If any discrepancy is detected, prior to further flight, repair in accordance with the procedures specified in the Boeing 747 Maintenance Manual. Additionally, prior to further flight, the functional test must be successfully accomplished. Repeat the functional test thereafter at intervals not to exceed 3,000 flight hours.
(f) If, after incorporation of the modification required by paragraph (d) of this AD on any airplane, it becomes necessary to install a thrust reverser assembly that does not have the TRAS locks installed, dispatch of the airplane is allowed in accordance with the provisions and limitations specified in the operator's FAA-approved MEL, provided that the thrust reverser assembly that does not have the TRAS locks installed is deactivated in accordance with Section 78-1 of Boeing Document D6-33391, “Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,” Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph. Within 10 days after deactivation of the thrust reverser, install a thrust reverser assembly that has the TRAS locks installed and reactivate the thrust reverser.
(g) If, prior to incorporation of the modification required by paragraph (d) of this AD on any airplane, it becomes necessary to install a thrust reverser assembly that has the TRAS locks installed, dispatch of the airplane is allowed in accordance with the provisions and limitations specified in the operator's FAA-approved MEL, provided that the thrust reverser assembly that has the TRAS locks installed is deactivated in accordance with Section 78-1 of Boeing Document D6-33391, “Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,” Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph. Within 10 days after deactivation of the thrust reverser, install a thrust reverser assembly that does not have the TRAS locks installed and reactivate the thrust reverser.
