AD/BO 105/16 Amdt 1 Tension-Torsion Strap (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/BO 105/16 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 BO 105 Series Helicopters

AD/BO 105/16 Amdt 1 Tension-Torsion Strap 7/2008 DM

Applicability:

All Eurocopter Canada Model BO 105 LS-A3 helicopters.

Requirement:

1.    Verify the following:

The time accumulated since last part installation (years);

Number of flight hours since last installation; and,

Number of flights since last installation, in accordance with section 1.D. Compliance of Eurocopter Canada Alert Service Bulletin (ASB) BO 105
LS-10-10 Revision 1, or later Transport Canada approved revision.

2.    Based on verification results above, establish the new service life limitation and inspection schedule for those parts that have qualified in accordance with applicable paragraphs of section 1.D. of the ASB.

3.    Inspect all parts for damage in accordance with section 2.B.2. of the ASB.

4.    Replace those parts that were identified for replacement as a result of the above verification and inspection.  Follow instructions provided in paragraphs 1.D.1. through 1.D.5. and 2.B.1 through 2.B.2., of the ASB.  Scrap replaced parts.

5.    Re-identify (renumber) those parts that are eligible (as per sections 1.D.6. and 1.D.7.) including main rotor heads, in accordance with paragraph 2.B.1.2. of the ASB.

Enter into the historical records the technical data related to corrective actions, as required by paragraphs 2.B.1.3. and 2.B.1.4. of the ASB.

Note:  Transport Canada AD CF-2008-17 refers.

Compliance:

1.    Within 25 flight hours after 27 May 2008, but no later than 6 June 2008.

2.    As soon as practicable, but no later than 10 June 2008.

3.    Within 50 flight hours after 27 May 2008.

4.    As required by Requirement 4.

5.    Within 50 flight hours after 27 May 2008.

This Amendment becomes effective on 27 May 2008.

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.

Amendment 1 is issued in response to a new Transport Canada AD, which requires recalculation of time-in-service and sets new inspection criteria for tension-torsion straps.  As a result of this change, tension-torsion straps in service are to be replaced or inspected as a precautionary measure, based on accumulated service hours and the calendar time since their last installation.

David Villiers
Delegate of the Civil Aviation Safety Authority

21 May 2008