What happened
On 15 July 2002, a Sikorsky S-61N, registration G-BBHM, was conducting a search and rescue mission in Poole Harbour on behalf of HM Coastguard. After responding to an alert regarding a person in the water, the crew was redirected to investigate reports of a smoking vessel. During this transit, the crew noticed an unusual noise, followed immediately by a fire warning for the number two engine.
Smoke was observed exiting the engine exhaust area and entering the cabin. The commander initiated an emergency climb and turn toward Bournemouth Airport, declaring an emergency via radio. As the crew attempted to manage the fire, several other warnings appeared, including low transmission oil pressure and loss of hydraulic servo pressure. The pilot also experienced uncommanded lateral movement in the cyclic control.
Recognizing the deteriorating situation, the commander opted for an immediate landing at a nearby sports field. Despite the increasing density of smoke in the cabin, the pilot successfully landed the aircraft. The 4 crew members evacuated the helicopter safely, but the aircraft was destroyed by fire shortly after touchdown.
The investigation
The AAIB examined the wreckage and recovered flight data from the cockpit and flight data recorder. Preliminary analysis of the flight recorder showed that the interval between the initial fire warning and the landing was only 80 seconds.
Engineering inspections of the wreckage revealed that the fire originated in the vicinity of the number two engine. Investigators identified evidence of mechanical distress near the high-speed shaft of the engine. The investigation focused on the condition of the Thomas flexible coupling within the main drive shaft and its interaction with the engine support structure.