AD/EC 120/14 Amdt 1 Tail Rotor Driveshaft Rear Driveshaft Friction Ring (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/EC 120/14 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.

Eurocopter EC 120 Series Helicopters

AD/EC 120/14 Amdt 1 Tail Rotor Driveshaft - Rear
Driveshaft Friction Ring 11/2007

Applicability:

Eurocopter EC 120 B helicopters equipped with rear drive shafts, Part Numbers (P/N) C651A3102051 and C651A3102052.

Requirement:

1.    Check that the friction ring has not moved on the rear drive shaft, in accordance with the instructions specified in paragraph 2.B. of Eurocopter EC 120 Alert Service Bulletin (ASB) No. 05A006 or later approved revisions.

2.    Results and further mandatory actions after accomplishment of Requirement 1 of this AD:

(a)   If the friction ring has not moved, leave as it is and resume flights.

(b)   If the friction ring has moved, or if in doubt, comply with instructions given in paragraph 2.B.2 of EUROCOPTER EC120 ASB No. 05A006 initial issue or later approved revision, in order to ensure any ring actually found unstuck cannot move further freely when trying to move it by hand;

-      if the unstuck friction ring moves further, replace the rear element of the tail rotor drive shaft.

-      if the unstuck friction ring does not move further, turn the rear element of the tail rotor drive shaft by 180°, provided that it has never been turned during previous compliance with aircraft maintenance tasks, otherwise replace this rear shaft element.

Note:  EASA AD 2007-0211 dated 7 August 2007 refers.  This AD supersedes DGAC AD F-2005-076.

Compliance:

1.    Remains unchanged as detailed in the original issue of this AD as:

For Helicopters that have logged less than 90 flying hours:  Within 110 flying hours from 13 May 2005, and then, repetitively, at intervals not exceeding 110 flying hours.

For Helicopters that have logged 90 flying hours or more:  Within 20 flying hours from 13 May 2005, and then, repetitively, at intervals not exceeding 110 flying hours.

2.a. From the effective date of this AD.

2.b. Before further flight.

This Amendment becomes effective on 25 October 2007.

Background:

There have been reports of bonding failure and displacement of the damper friction ring on the rear drive shaft, resulting in incorrect positioning and differential wear on the two damper half clamps.  Such wear may cause failure of the rear drive shaft.

The actions specified in this AD address the risks associated with the failure of rear driveshaft.

This amendment reflects conversion, conversion of EUROCOPTER Alert Telex No. 05A006, to an ASB with the corresponding number without affecting the overall technical content itself but clarifying that repetitive inspections must be continued whether the rear shaft element is replaced or simply rotated by 180° in order to use the second friction ring let available on the shaft as a spare.

The original issue of this AD became effective on 13 May 2005.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

10 September 2007