AD/PR/40 Propeller Backplate Sealant (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.

Propellers - Variable Pitch - Dowty Rotol

AD/PR/40 Propeller Backplate Sealant 9/2009

Applicability:

Dowty Propellers Model R408/6-123-F/17 propellers, all serial numbers (S/N).

Note 1:  These propellers are known to be installed on, but not limited to, Bombardier DHC-8-400, DHC-8-401 and DHC-8-402 aeroplanes.

Note 2:  AD/DHC-8/144, applicable to Bombardier DHC-8 Series 400 aeroplanes, was issued for the same unsafe condition that is addressed by this AD.

Requirement:

1.    Apply sealant between the bus bar assemblies and the backplate assembly in accordance with the instructions of Dowty Propellers Alert Service Bulletin (ASB) D8400-61-66 dated 9 February 2007.

All affected Hub, Actuator and Backplate Assembly Line-Replaceable Units (LRU) with s/n DAP0347 and higher have received the initial sealant application prior to delivery/installation and are therefore already compliant with Requirement 1 of this AD.

2.    Re-apply sealant between the bus bar assemblies and the backplate assembly in accordance with the instructions of Dowty Propellers ASB D8400-61-66.

3.    Do not install any Dowty R408/6-123-F/17 propeller on that aeroplane, unless sealant has been applied between the bus bar assemblies and the backplate assembly of that propeller in accordance with the requirements of this AD.

The use of later approved revisions of this document is acceptable for compliance with requirements of this AD.

Note 3:  EASA AD 2009-0114 dated 28 May 2009 refers.

Compliance:

For Requirement 1 - Within the next 5,000 flight hours (FH) after the effective date of this AD, unless previously accomplished.

Compliance with Requirement 2 of AD/DHC-8/144 also satisfies Requirement 1 of this AD.

For Requirement 2 - Prior to accumulating 10,000 FH after the initial sealant application and thereafter at intervals not to exceed 10,000 FH.

For Requirement 3 - After modification of all propellers on an aeroplane as required by Requirement 1 of this AD.
This Airworthiness Directive becomes effective on 27 August 2009.
Background:	Friction or contact between the propeller de-ice bus bar and the backplate assembly can cause failure of the bus bar and a consequent intermittent short circuit.  Such a short circuit can cause a dual AC generator shutdown that, particularly in conjunction with an engine failure in icing conditions, could result in reduced controllability of the aeroplane.

James Coyne
Delegate of the Civil Aviation Safety Authority

15 July 2009