AD/BO 105/16 Tension-Torsion Strap (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 BO 105 Series Helicopters

AD/BO 105/16 Tension-Torsion Strap 10/2007

Applicability:

All Eurocopter Canada Model BO 105 LS-A3 helicopters.

Requirement:

Action in accordance with the requirements of Transport Canada AD CF-99-24R1.

Following compliance with this Directive, tension-torsion straps are to be replaced upon accumulating 10 years or 40,000 flight hours of operation, whichever occurs first.

Note:  Eurocopter Canada ASB BO105 LS-10-10 dated 1 September 1999 or later Transport Canada approved revision refers.

Compliance:

Unless already accomplished, as specified in the Requirement document, with a revised effective date of 27 September 2007.

This Airworthiness Directive becomes effective on 27 September 2007.

Background:

A tension-torsion strap ruptured in the main rotor head of a Model MBB BK 117 helicopter in 1999.  The ensuing separation of a main rotor blade led to the total loss of the helicopter.  The tension-torsion straps of the affected helicopter are of the same design as the accident helicopter, but are subjected to a lower stress loading.  As a precautionary measure, this Directive requires that in-service tension-torsion straps are replaced and/or inspected dependent upon their accumulated flight hours and calendar time.

David Villiers
Delegate of the Civil Aviation Safety Authority

13 August 2007