AD/AL 250/81 - Third Stage Turbine Wheels (Cth)

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.

Allison Turbine Engines - 250 Series

AD/AL 250/81 Third Stage Turbine Wheels 6/2002

Applicability: Allison 250 - C28 Engines with third stage turbine wheels Part Number (P/N) 6899383 and with Serial Numbers (S/N) listed in Table 1 of this Directive.

Requirement: Remove from service all turbine wheels P/N 6899383 listed by S/N in Table 1 of this Directive.

Note: FAA AD 2002-06-08 refers.

Compliance: Effective 13 June 2002; as per Table 2 of this Directive.

This Airworthiness Directive becomes effective on 13 June 2002.

Background: Fractures of the third stage turbine blade tips and shrouds could cause uncommanded shutdowns. New lower life limits have been established to address this problem. This Directive requires the removal from service of certain turbine wheels that exceed the new lower life limits.

Table 1. S/N's of Affected Third Stage Turbine Wheels

HX91428R HX91489R HX91707R HX91456R HX91490R HX91708R HX91457R HX91492R HX91709R HX91428R HX91489R HX91707R HX91456R HX91490R HX91708R HX91457R HX91492R HX91709R HX91458R HX91493R HX91710R HX91459R HX91494R HX91711R