Ad/EC 120/16 - 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 EC 120 Series Helicopters

AD/EC 120/16 Engine Controls - Twist Grip Assembly 11/2006

Applicability:

EC 120 B helicopters equipped with a twist grip assembly, part numbers (PN):

- C761A2024102 and C761A2024103, all serial numbers (SN),

- C761A2024104 with SN below 0418,

- C761A2025102 and C761A2025103, all SN,

- C761A2025104 with SN below 0382.

Requirement:

1. Check the bonding between the pilot and co-pilot collective lever drive tubes and the control pinions, by applying a load to the twist grip, in accordance with paragraphs 2.B.1 and 2.B.2 of Eurocopter EC 120 Alert Service Bulletin No. 76A006 R1 or later DGAC approved revision.

2. If the twist grip turns when applying the load to the twist grip replace the collective lever, in accordance with paragraph 2.B.3. of Eurocopter EC 120 ASB No. 76A006 R1 or later DGAC approved revision.

3. Comply with the instructions specified in paragraph 2.B.4. of Eurocopter EC 120 ASB No. 76A006 R1 or later DGAC approved revision.

Note:  EASA AD 2006-0253 dated 22 August 2006 refers.

Compliance:

1.    No later than within 50 flying hours or 2 months, whichever occurs first after the effective date of this AD.

2.    Before further flight after the effective date of this AD.

3.    Before installation in a helicopter after the effective date of this AD.

This Airworthiness Directive becomes effective on 26 October 2006.

Background:

This Airworthiness Directive is in response to a twist grip failure experienced during an autorotation training procedure during which the engine remained at idle rating although the twist grip had been turned back to the flight position.

Analysis has revealed failure of the twist grip drive tube and control pinion bonded attachment due to non-compliant preparation of the bonding surfaces on the two components.

James Coyne
Delegate of the Civil Aviation Safety Authority

13 September 2006