AD/Ecureuil/120 Engine Controls Twist Grip Assembly (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.

Eurocopter AS 350 (Ecureuil) Series Helicopters

AD/ECUREUIL/120 Engine Controls - Twist Grip Assembly 9/2006 DM

Applicability:	AS 350 B3 helicopters, equipped with twist grips, before the embodiment of MOD 073261 (new twist grip assemblies compatible with the Arriel 2B1 engine installation).
Requirement:	1.    If not previously accomplished, adjust the ‘forced idle’ microswitch and check it for correct operation, in accordance with paragraph 2.B.2. and 2.B.3. of Eurocopter Alert Service Bulletin (ASB) 05.00.49 dated 1 February 2006, or later EASA approved revision.
2.    Accomplish a functional test of the of the ‘forced idle’ microswitch in accordance with paragraph 2.B.3. of ASB 05.00.49, or later EASA approved revision.
3.    Replace the ‘forced idle’ microswitch in accordance with paragraph 2.B.4. of ASB 05.00.49, or later EASA approved revision.
Note 1:  EASA AD 2006-0094 refers.
Compliance:	For Requirement 1 - Within 110 hours time in service (TIS) after the effective date of this Directive.
For Requirement 2 - Within 110 hours TIS after the Requirement 1 check and thereafter at intervals of not less than 110 hours TIS.
For Requirement 3:
Helicopters with less than 440 hours total TIS - Before the accumulation of 550 hours total TIS and thereafter at intervals of not less than 550 hours TIS.
Note 2:  Helicopters with less that 440 hours total TIS at the effective date of this Directive may have to comply with the Requirement 2 functional check before the microswitch is required to be replaced.
Helicopters with 440 or more hours total TIS - Within 110 hours TIS after the effective date of this Directive and thereafter at intervals of not less than 550 hours TIS.
This Airworthiness Directive becomes effective on 26 July 2006.

Background:	The European Aviation Safety Agency (EASA) has advised of an incident during an autorotation training procedure where the engine remained a idle rating although the twist grip had been turned back to the ‘FLIGHT’ position.
Analysis revealed that the ‘forced idle’ microswitch pin had jammed in the pushed-in position.  The jamming resulted in the engine speed being held at ‘forced idle’.
This Directive requires the initial adjustment and check of the microswitch, followed by receptive inspections and replacement.

James Coyne
Delegate of the Civil Aviation Safety Authority

20 July 2006