Fire Warning Light Did Not Activate During Function Test

The Civil Aviation Safety Authority of Australia has issued an "urgent" AD for AS 350 B2 helicopters, all serial numbers, if equipped with a Turbomeca ARRIEL 1D1 engine and incorporating Eurocopter modification (mod) 073273, except helicopters that incorporate mod 074346. The AD was first published by EASA.

Reports have been received, concerning three events with AS 350 B2 helicopters, in which the "FIRE ALARM" warning did not light up on the Cockpit Warning Panel (CWP) during a functional test of the power plant fire detection circuit. The results of the investigation showed that these occurrences had been caused by the fact that a resistor was missing, which had been introduced through mod 072598, but removed through mod 073273 even though mod 072598 was still logged in the helicopter documents.

This condition, if not detected and corrected, could lead to a situation where an engine fire remains undetected, possibly resulting in loss of the helicopter. For the reasons described above, this AD requires modification of the fire detection system (mod 074346) by installation of two additional resistor modules (38W and 39W).

Unless accomplished previously, within 40 flight hours or 75 calendar days, whichever occurs first after the effective date of this AD, modify the fire detection system by installing resistor modules 39W and 38W, in accordance with the instructions of paragraph 3 of Eurocopter AS350 Emergency Alert Service Bulletin (ASB) 26.00.02.

FMI: http://casa.gov.au/