Ad/Arrius/16 - Engine Fuel and Control - P3 Air Pipe (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.

Turbomeca Turbine Engines - Arrius Series

AD/ARRIUS/16 Engine Fuel and Control - P3 Air Pipe 10/2008

Applicability:

TURBOMÉCA ARRIUS 2F turbo-shaft engines.

Note 1:  These engines are installed in, but not limited to Eurocopter EC120B helicopters.

Requirement:

Carry out the following instructions in accordance with Turbomeca Mandatory Service Bulletin N° 319 75 4810 or later approved revision:

a.     Visually inspect P3 air pipe (first section) and RH rear half-wall.

b.    Inspect play between P3 air pipe (first section) and RH rear half-wall.

c.     Replace P3 air pipe (first section) if any damage is found.

d.    Re-adjust the first section of the P3 air pipe if the inspected clearance is found to be incorrect.

e.     Replace RH rear half-wall if any damage is found.

Note 2:  EASA AD 2008-0134 dated 17 July 2008 refers.

Compliance:

Within 100 operating hours after the effective date of this AD.

This Airworthiness Directive becomes effective on 25 September 2008.

Background:

On several ARRIUS 2F engines, the clearance between the P3 air pipe part number (P/N) 0319719180 and the rear right bulkhead P/N 0319998240 has been found to be too small.

Investigations have shown that both P3 air pipe and rear right bulkhead were compliant to the design.  The Turbomeca Engineering Department concluded that the tolerance of assembly established during the design could result in some rubbing between parts.

Rubs between the pipe and the bulkhead may lead to premature wearing and finally rupture of the P3 air pipe.  The loss of P3 air pressure would then force the fuel control system to idle which could have a detrimental effect in critical phases of flight.

James Coyne
Delegate of the Civil Aviation Safety Authority

25 July 2008