AD/Dauphin/99 Fuel Crossfeed High Level Switches (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 SA 360 and SA 365 (Dauphin) Series Helicopters

AD/DAUPHIN/99 Fuel Crossfeed High Level Switches 7/2009 TX

Applicability:

SA 365 N and SA 365 N1 helicopters, all serial numbers, except those incorporating modification kit 365A087690.00 or modification 0728B17 (removal of the two high level switches from helicopters equipped with a crossfeed between the fuel filler necks).

Requirement:

1.    Disconnect the fuel high level switches in accordance with the instructions of paragraph 2.B.1 of Eurocopter AS365 Alert Service Bulletin (ASB) 01.00.63.

2.    On helicopters not equipped with a crossfeed between the fuel filler necks, install a placard near the fuel panel in accordance with the instructions of paragraph 2.B.2 of Eurocopter AS365 ASB 01.00.63 dated 5 May 2009.

Later revisions of ASB 01.00.63 approved by the European Aviation Safety Agency are acceptable for compliance with this Directive.

Note:  EASA Emergency AD 2009-0109-E refers.

Compliance:

For Requirements 1 and 2 - Within 10 hours time in service or 30 days, whichever occurs first after the effective date of this Directive.

This Airworthiness Directive becomes effective on 8 May 2009.

Background:

One SA 365 N operator noted that the high level switch probe unit, located in the rear (right hand) auxiliary fuel tank group had separated.  This caused damage to the insulation of the electrical wires which supply the high level indicator light on the fuel control panel during a fuel transfer.

This condition, if not detected and corrected, could lead to exposure of the electrical wires, potentially causing a short circuit and subsequent lighting of the indicator light without the high fuel level actually being reached.  In addition, a short circuit could become a potential ignition source inside the fuel tank which, in combination with flammable fuel vapours (if present), could result in a fuel tank explosion and consequent loss of the helicopter.

For the reasons described above, this Directive requires the disconnection of the high level switches on the affected helicopters.  Disconnecting the switches inhibits the high (fuel) level warning system which normally informs the flight crew of the risk of fuel overflowing from the tank vents.  To mitigate that risk, this Directive also requires, for certain helicopters, the installation of a placard near the fuel panel, limiting the transfer of fuel between fuel tank groups to cases where the receiving fuel tank group contains less than 300 litres (240 kg or 529 lbs).

This Directive is considered to be a temporary measure and further rulemaking is likely to follow.

James Coyne
Delegate of the Civil Aviation Safety Authority

8 May 2009