AD/B747/273 - Thrust Reverser Flow Restrictor (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Boeing 747 Series Aeroplanes

AD/B747/273 Thrust Reverser Flow Restrictor 7/2002

Applicability: Model 747-400 series aeroplanes up to and including line position 1022, powered by Pratt and Whitney PW 4000 series engines.

Requirement: Replace the thrust reverser flow restrictor devices with one-way (check) valve restrictors in accordance with Boeing Alert Service Bulletin 747-78A2128, dated 10 March, 1994; or Revision 1, dated 26 May, 1994.

Note: FAA AD 94-20-11 Amdt 39-9040 refers.

Compliance: Prior to further flight.

This Amendment becomes effective on 11 July 2002.

Background: The manufacturer has reported several instances of thrust reverser sleeve actuator piston seal leakage during overhaul. Testing done by Boeing suggests that if there is sufficient seal leakage in two of the three actuators on a single sleeve, then a sleeve deployment could occur. This Directive introduces a modification to prevent the possibility of an uncommanded in- flight deployment of a thrust reverser.