Ad/Gazelle/32 - Goodrich Hoist Pyrotechnic Squibs (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 SA341 and SA342 (Gazelle) Series Helicopters

AD/GAZELLE/32 Goodrich Hoist Pyrotechnic Squibs 12/2005 TX

Applicability:

SA 341 G and SA 342 J helicopters equipped with a Goodrich electric hoist part number 76370-XXX fitted with any type of electric motor except one manufactured by Auxilec.

Note 1:  The motor manufacturer is indicated on the identification plate of the motor.

Requirement:

Accomplish the following in accordance with Paragraph 2.B. of Eurocopter SA 341/342 Alert Telex 25.12 or later revision approved by the French Direction Générale de l’Aviation Civile (DGAC):

a.     Inhibit operation of the hoist pyrotechnic squib,

b.    Install suitable cable cutting shears, and

c.     Install two warning placards.

Note 2:  DGAC AD UF-2005-161 (EASA Approval 2005-6248) refers.

Compliance:

Before the next hoisting operation after the effective date of this Directive.

This Airworthiness Directive becomes effective on 21 September 2005.

Background:

Eurocopter has received advice of a squib firing on a AS 355 F2 helicopter without being triggered by either the pilot or the hoist operator. The hoist motor brush power supply wiring was found to be earthed to the casing of the hoist motor. The ground caused leakage current to the squib firing components, which triggered the untimely firing of the squib and cutting of the hoist cable.

The same type of hoist is also installed on Gazelle helicopters.  Notwithstanding that Gazelle helicopters are fitted with a resistor in the squib circuit capable of absorbing the leakage current energy and thus reducing the risk of untimely firing, it does not guarantee full effectiveness.  This Directive requires the firing of the squib to be inhibited, installation of cable cutting shears and the installation of warning placards.

Further rulemaking may be anticipated following development of a suitable modification.

James Coyne
Delegate of the Civil Aviation Safety Authority

19 September 2005