What happened
On 18 April 2011, an AS3/65N3 Dauphin II, registration G-REDG, was preparing for a routine commercial passenger and freight flight to the Pickerill B oil platform. During taxiing at Norwich Airport, a ground engineer noticed flames and blue/black smoke emanating from the No 1 engine.
Because there was no direct way for ground staff to alert the crew, the engineer chased the helicopter along the taxiway and used hand signals to communicate. The crew, initially unaware of the fire, responded to the shutdown signal. The engineer then used a handheld extinguisher to put out a small oil-fed fire in the engine bay. The passengers were evacuated from the helicopter via the left-side door.
The investigation
The investigation examined the maintenance history and the communication chain during the incident. The aircraft had recently undergone a 600-hour maintenance check where seals on the engine oil ducts were replaced. While a leak had been identified and corrected on the No 2 engine during post-maintenance ground runs, no leak was noted on the No 1 engine at that time.
Investigators also looked into the delay in emergency response. The engineer' and a handling agent both attempted to contact the crew via the company radio frequency, but the crew's radio was set to the ATC tower frequency. Furthermore, the airport's emergency plan relied on the Duty Airfield Operations Officer (DAOO) to marshal passengers, but the officer was unavailable as they were assisting with a vehicle recovery elsewhere.
Findings
- The fire was caused by oil leaking from the lower connection of the oil supply duct onto the hot engine casing.
- The leak likely originated from improper torque applied to the duct during maintenance; it is suspected the duct was rotated anti-clockwise during refitting, which reduced the torque from the required 20 Nm to 10 Nm.
- The crew did not receive an internal warning from the aircraft's fire detection system, and there were no abnormal engine indications prior to the fire.
- Communication delays occurred because the aircraft radio was not on the handling agent's frequency and the airport lacked a dedicated emergency reporting line for airside staff.