AD/GBK 117/22 Tail Rotor Balance Weights (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 BK 117 Series Helicopters

AD/GBK 117/22 Tail Rotor - Balance Weights 2/2009

Applicability:

Eurocopter Deutschland (ECD) GmbH Models MBB-BK 117 A-1,
MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK 117 B-1, MBB-BK 117 B-2 and MBB-BK 117 C-1 helicopters, all serial numbers.

Requirement:

1.    Inspect the tail rotor balance weights and control levers in accordance with ECD BK117 Alert Service Bulletin (ASB) No. MBB-BK117-30-113.

2.    If, during any inspection as detailed in Requirement 1 of this AD, damage is detected which exceeds the acceptable limits as specified in the ASB, replace the affected components with serviceable parts.

Replacement of parts does not constitute terminating action for the repetitive inspection requirements of this AD.

Note:  EASA AD 2008-0206 dated 25 November 2008 refers.

Compliance:

For Requirement 1 - Within the next 2 months or 100 flight hours (FH), whichever occurs first after the effective date of this AD, and thereafter at intervals not to exceed 600 FH (+ 60 FH) or 48 months (+ 6 months), whichever occurs first.

For Requirement 2 - Before further flight.

This Airworthiness Directive becomes effective on 12 February 2009.

Background:

During a periodical inspection, corrosion was detected on the tail rotor balance weights in the area of the attachment thread.  This condition, if not detected and corrected, could lead to failure of the threads, possibly resulting in separation of tail rotor parts, subsequent severe tail rotor vibration and consequent loss of control of the helicopter.

For the reasons described above, this AD requires repetitive visual inspections of the tail rotor balance weights and control levers to identify any damage and the replacement of damaged components.

James Coyne
Delegate of the Civil Aviation Safety Authority

22 December 2008