AD/APU/20 Hamilton Sundstrand Compressor Impeller Assemblies (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 39.001(1) of CASR 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.

Auxiliary Power Units

AD/APU/20 Hamilton Sundstrand Compressor
Impeller Assemblies 3/2006

Applicability:

Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems) auxiliary power units (APUs) models T-62T-46C2, T-62T-46C2A, T-62T-46C3, T-62T-46C7, and T-62T- 46C7A, with compressor impeller assembly, part number (P/N) 4502020 or 4502020A installed.

Note 1:  These APUs are installed on, but not limited to, BAE Systems AVRO 146, Fokker 50, Saab 2000, and Saab 340 aeroplanes.

Requirement:

Remove compressor impeller assemblies from service.

Note 2:  FAA AD 2005-23-11 Amdt 39-14369 refers.

Compliance:

For APUs with compressor impeller assemblies that have 12,000 or more cycles-since-new (CSN) accumulated on the effective date of this AD; before accumulating 500 additional cycles.

For APUs with compressor impeller assemblies that have fewer than 12,000 CSN on the effective date of this AD; before accumulating 12,500 CSN.

This Airworthiness Directive becomes effective on 16 March 2006.

Background:

This AD results from two reports of uncontained failures of compressor impeller assemblies.  The issuing of this AD is to prevent an uncontained APU failure and damage to the aeroplane.

James Coyne
Delegate of the Civil Aviation Safety Authority

1 February 2006