Ad/Thielert/11 Amdt 3 - Propeller Control Valve (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) AD/THIELERT/11 Amdt 2 and issues the following 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.

Thielert Piston Engines

AD/THIELERT/11 Amdt 3 Propeller Control Valve 11/2009 DM

Applicability:

Thielert Aircraft Engines (TAE) GmbH TAE125-01 engines that are installed on Diamond Aircraft Industries DA 42 aeroplanes.

Note 1:  TAE125-01 engines installed on other aeroplane types are not concerned by this AD.

Requirement:

Inspect and/or replace the electrical connectors of the Proportional Pressure Reducing Valve and install a vibration isolator between the engine gearbox and the propeller’s Constant Speed Unit as instructed in steps 1 to 27 of the Thielert Service Bulletin
TM TAE 125-0020 initial issue.

Note 2:  If not already been done, step 22 of the Thielert Service Bulletin TM TAE 125-0020 initial issue calls for the initial replacement of the PPRV in accordance with Thielert Service Bulletin TM TAE 125-0018 revision 1.

Note 3:  The vibration isolator and the PPRV are part of the gearbox assembly.  They must be inspected regularly in accordance with the Engine Operation & Maintenance Manual OM-02-01 and the Engine Repair Manual RM-02-01.

The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD.

Note 4:  EASA AD 2009-0193 dated 27 August 2009 refers.

Compliance:

Within 55 Flight Hours after the effective date of this AD, unless previously accomplished.

This Amendment becomes effective on 24 September 2009.

Background:

Engine In-Flight Shutdown (IFSD) incidents have been reported on Diamond Aircraft Industries DA 42 aeroplanes equipped with TAE125 engines.  The investigations showed that it was mainly the result of failure of the Proportional Pressure Reducing Valve (also known as Propeller Control Valve) due to high vibrations.

To address this subject, this AD mandated a life-limit for the Proportional Pressure Reducing Valve (PPRV).  Since the release of this AD, the engine gearbox has been identified as the primary source of vibrations for the PPRV, and it has also been determined that failure of the electrical connection to the Proportional Pressure Reducing Valve can have contributed to some power loss events or IFSD.

This amendment mandates installation of a vibration isolator between the engine gearbox and the propeller Constant Speed Unit (CSU).  In addition, it requires an inspection of the electrical connectors of the PPRV.  Installation of the vibration isolator entails the replacement of the de-icing nozzle support bracket and replacement of the CSU aluminium pipe with a flexible hose.

The original issue of this AD became effective on 29 July 2008.

Amendment 1 of this AD became effective on 22 August 2008.

Amendment 2 of this AD becomes effective on 24 September 2009.

James Coyne
Delegate of the Civil Aviation Safety Authority

10 September 2009