AD/AS 355/91 Upper and Lower Fins of Stabilisers (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 355 (Twin Ecureuil) Series Helicopters

AD/AS 355/91 Upper and Lower Fins of Stabilisers 9/2006

Applicability:

Model AS 355 helicopter versions E, F, F1, F2, and N, with Eurocopter Alert Service Bulletin No. 55.00.11 incorporated.

Requirement:

1.    For helicopters equipped with upper and lower fins pre-MOD 073288:

a.     Replace the upper fin and lower fin attachment screws in accordance with paragraph 2.B.2. of Eurocopter AS 355 Alert Service Bulletin (ASB)
No. 55.00.11, or later EASA approved revision.

b.    Check the tightening torque of the upper fin attachment screws and inspect the upper fin reinforcement splice for cracks and loose rivets, in accordance with paragraph 2.B.3. of ASB No. 55.00.11, or later EASA approved revision.

2.    For helicopters equipped with upper and lower fins post-MOD 073288:

Check the tightening torque of the upper fin attachment screws and inspect the upper fin reinforcement splice for cracks and loose rivets, in accordance with paragraph 2.B.3. of ASB No. 55.00.11, or later EASA approved revision.

Note 1:  Compliance with the requirements of ASB No. 55.00.11 cancels and replaces the corrective actions mandated by EASA AD 2006-0096 (AD/AS 355/84 Amdt 1).

Note 2:  EASA AD 2006-0097 refers.

Compliance:

1.a. Within 110 flight hours after 31 August 2006, unless already accomplished.

1.b. Within 110 flight hours after accomplishment of Requirement 1.a., and thereafter at intervals not to exceed 110 flight hours.

2.    Unless the initial check/inspection is already accomplished, within 110 flight hours after 31 August 2006.  Thereafter at intervals not to exceed 110 flight hours.

This Airworthiness Directive becomes effective on 31 August 2006.

Background: Reports were received of cracks discovered in the spar of the upper vertical fin on two AS 355 N helicopters.  Undetected cracking on the attachment spar of a vertical fin could lead to failure of the spar, and result in loss of the vertical fin.

David Villiers
Delegate of the Civil Aviation Safety Authority

20 July 2006