AD/GBK 117/18 Tail Rotor System Control Lever Inspection/Replacement (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 117/18 Tail Rotor System - Control Lever - Inspection/Replacement 9/2007

Applicability:

MBB-BK 117C-2 helicopters, Serial Number (S/N) 9075 through 9122;

and S/N 9004 through 9074 on which Service Bulletin MBB BK117 C-2-67-006 has already been accomplished.

Requirement:

Unless previously accomplished:

1.    For helicopters that have not been inspected as required by EAD 2006-0379-E, visually inspect the control lever, inspect in accordance with section 3.A of the accomplishment instructions of EUROCOPTER DEUTSCHLAND Alert Service Bulletin (ASB) MBB BK117 C-2-64A-002 Revision 01 dated 9 July 2007 or subsequent EASA approved revision.

2.    For helicopters that have been inspected as required by EAD 2006-0379-E, repeat the inspection as specified in paragraph (1) of this directive;

3.    Repeat the inspection as specified in paragraph (1) of this directive;

4.    If, during any of the inspections required by this directive, score marks, notching, scratching, cracks or similar damage is detected, replace the affected control lever with an airworthy part.

Note: 1:  EASA AD No. 2007-0189-E refers.

Compliance:

1.    Before next flight after the effective date of this directive,

2.    Within the next 8 flight hours (FH) or before accumulating 25 FH after the last inspection as required by EAD 2006-0379-E, whichever occurs first after the effective date of this directive,

3.    At intervals not to exceed 8 FH,

4.    Before next flight.

This Airworthiness Directive becomes effective on 30 August 2007.

Background:

EASA was informed by the manufacturer of an in-flight incident in which a dynamic weight broke off the control lever subsequently leading to considerable vibrations.  A visual inspection revealed that the threaded bolt of the control lever had broken off. For this reason, the manufacturer issued the Alert Service Bulletin MBB BK117
C-2-64A-002 to introduce a corresponding visual inspection.

EASA subsequently issued Emergency AD 2006-0379-E to require operators to accomplish the inspection.  The aim of that EAD was to prevent separation of dynamic weights in flight, which can lead to severe vibration and reduced controllability of the helicopter.

The present Emergency AD retains the requirements of EAD 2006-0379-E, reduces the inspection interval and limits the s/n applicability, pending the approval of the terminating action.  This is expected to result in the issuance of another airworthiness directive, mandating the replacement of the control lever with an improved part.

David Punshon
Delegate of the Civil Aviation Safety Authority

13 July 2007