AD/AL 250/77 Third Stage Turbine Wheel P/N 23001977 Cancelled (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive AD/AL 250/77.

Allison Turbine Engines - 250 Series

AD/AL 250/77 Third Stage Turbine Wheel P/N 23001977 7/2009

Requirement:

CANCELLED.

This AD is cancelled on 2 July 2009.

Background:

This unique Australian AD raised in 1996 against Allison Commercial Engine Bulletin (CEB) 250 CEB-A-72-2176 required replacement of all 250-C28 series engine third stage turbine wheel P/No. 23001977 following a contained failure where a small portion of the blade shroud separated from the wheel.  A life was established at 50 hours TSN.

Compliance was:  Effective 2 February 1996; as detailed in the requirement document, which was:

All P/No. 23001977 third stage turbine wheels must be removed from service upon reaching 50 hours TNS.  Any P/No. 23001977 turbine wheel with more than 50 hours TSN must be removed from service within the next ten (10) flight hours.

This AD has been sufficiently promulgated for the affected engine turbine wheels to have been replaced by now; therefore this AD is considered to be no longer required.

James Coyne
Delegate of the Civil Aviation Safety Authority

1 May 2009