AD/AL 250/18 Compressor Bleed Valve Orifice Installation 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 250/18.

Allison Turbine Engines - 250 Series

AD/AL 250/18 Compressor Bleed Valve Orifice - Installation 6/2009

Requirement:

CANCELLED.

This AD is cancelled on 4 June 2009.

Background:

This unique Australian AD raised in 1973 against Allison Commercial Engine Bulletin (CEB) 250 CEB-107 required a modification to the engine compressor bleed valve by installation of an orifice (jet assy.) to delay the closing of the bleed valve on rapid acceleration to prevent surging under certain helicopter operational conditions.

Compliance was:  Before 31 July 1973.

This AD has been sufficiently promulgated for the affected engines to have been modified by now; therefore this AD is considered to be no longer required.

James Coyne
Delegate of the Civil Aviation Safety Authority

24 April 2009