AD/EC 135/21 Amdt 2 Rear Structure / Tail Boom (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/EC 135/21 Amdt 1 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 EC 135 Series Helicopters

AD/EC 135/21 Amdt 2 Rear Structure / Tail Boom 12/2009

Applicability:

Models EC135 P1(CDS), EC135 P1(CPDS), EC135 P2(CPDS), EC 135 P2+,
EC 135 T1(CDS), EC 135 T1(CPDS), EC 135 T2(CPDS), EC 135 T2+,
EC 635 T1(CPDS), EC 635 P2+ and EC 635 T2+ helicopters, all serial numbers, if an aft ring frame Part Number (P/N) L535A3501230 is installed.

Requirement:

1.    Amend the basic Flight Manual (FLM), Section 4 Pre-Flight Check, by inserting page 6 or 7 (as applicable) of Eurocopter Deutschland (ECD) EC135 Alert Service Bulletin (ASB) EC135-53A-022 original issue, or later EASA approved revision, into the FLM; and inform the flight crew accordingly.

2.    Accomplish the visual check of the rear structure tube in accordance with ECD ASB EC135-53A-022 original issue, or later EASA approved revision.

The pilot is permitted to accomplish this inspection as part of the regular pre-flight checks, provided he/she has been trained to do the inspection by an appropriately qualified person.

3.    Accomplish a visual inspection in accordance with ECD ASB EC135-53A-022 Revision 1, or later EASA approved revision.

If, during any inspection required by this Directive, cracks are detected within the ring frame as specified in the ASB, before further flight, replace the ring frame with a serviceable part.

Installation of a P/N L535A3501230 ring frame as a replacement part does not constitute terminating action for the repetitive check/inspection requirements of this Directive.

Modification (reinforcement) of the ring frame on a helicopter, in accordance with ECD Service Bulletin (SB) EC135-53-023, including P/N change to L535H2120302, constitutes terminating action for the repetitive check/inspection requirements of this AD for that helicopter.

Note 3:  EASA AD 2009-0065 R1 refers.

Compliance:

1.    Unless already accomplished, before further flight after 30 March 2009.

2.    Unless the initial inspection is already accomplished, before further flight after
30 March 2009, and thereafter before each first flight of a day.

3.    a.     Initial Inspection:

For aircraft that have accumulated 100 flight hours or less since new:

Before accumulating 110 flight hours.

For aircraft that have accumulated more than 100 flight hours since new:

Within 30 flight hours after the first Requirement 2 check, unless already accomplished.

3.    b.    Repeat Inspection:

At intervals not to exceed 110 flight hours.

This Amendment becomes effective on 19 November 2009.

Background:

During a recent pre-flight check on a Model EC135 helicopter, a crack was detected on the ring frame that connects the tail rotor Fenestron housing to the rear structure tube (tail boom).  The crack ran alongside one rivet row over almost half the circumference of the ring frame.  This condition, if not corrected, could lead to crack propagation remaining undetected, possibly resulting in loss of the Fenestron structure and loss of control of the helicopter.

Amendment 1 was issued in response to a new EASA AD, which expanded applicability and added a repetitive visual inspection to the AD requirements.  Based on in-service feedback, Eurocopter Deutschland revised ASB EC135-53A-022 to introduce a repetitive visual inspection of the rear fuselage structure (tailboom) for cracks.

This Amendment introduces the reinforcement of the aft ring modification, including P/N change to L535H2120302 as terminating action for the repetitive checks and inspections required by this Directive.

David Villiers
Delegate of the Civil Aviation Safety Authority

28 September 2009