AD/EC 120/14 Tail Rotor Driveshaft Rear Driveshaft Friction Ring (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 120/14 Tail Rotor Driveshaft - Rear
Driveshaft Friction Ring 7/2005 DM

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 Telex (AT) No. 05A006 dated 19 April 2005 or later EASA / DGAC approved revisions.

2.    On inspection per Requirement 1 of this Airworthiness Directive (AD), if the friction ring is found to have moved, comply with the instructions specified in paragraph 2.B.2 of Eurocopter EC 120 Alert Telex (AT) No. 05A006 dated 19 April 2005 or later EASA / DGAC approved revisions.

Note:  French Airworthiness Directive F-2005-076 approved under EASA reference No 2005-3955 dated 02 May 2005 refers.

Compliance:

1.    For Helicopters that have logged less than 90 flying hours:  Within 110 flying hours from the effective date of this AD 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 the effective date of this AD and then, repetitively, at intervals not exceeding 110 flying hours.

2.    Before further flight.

This Airworthiness Directive becomes effective on 13 May 2005.

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.

James Coyne
Delegate of the Civil Aviation Safety Authority

11 May 2005