A Norwich airport worker had to chase a helicopter along the runway and flag down the crew to stop it taking off after spotting flames coming from its engine.

The Dauphin II was carrying five passengers and two crew members for the routine flight to an oil platform last April.

But as it headed along the taxiway, a ground engineer noticed flames coming from one of the engines.

Attempts were made to contact the flight crew by radio and tell them to shut down the engines but they were unsuccessful.

A report by the Air Accidents Investigation Branch said: 'After leaving the operations room, the engineer ran after the helicopter in an attempt to alert the crew to the fire, which was now evidenced by smoke emanating from the engine compartment. The crew were unaware of the engineer until the passenger behind the co-pilot informed them.'

The engineer gave the crew the hand signals for 'shutdown' and 'fire'. The co-pilot later admitted he had not recognised the signal for fire but the commander had.

Passengers were escorted off the helicopter and the fire was put out with an extinguisher.

An investigation found the fire was likely to have been caused by an oil leak.

In its report the AAIB said communication problems, including failure to contact the crew by radio, had led to delays dealing with the emergency.

It said: 'Having noticed there was an engine fire, there was a delay in communicating this to the crew. As the engineer had already departed the pick-up point, the engineer took time to reach it. There was an additional delay due to his inability to attract the crew's attention, followed by confusion over the hand signals used.'

Three minutes are thought to have passed between the fire being spotted and the Rescue and Fire Fighting Service (RFFS) being contacted at about 8.39am on April 18.

The AAIB has called for clearer lines of communication for emergencies at the airport.

Since the fire, Norwich airport has reviewed its procedures and installed a dedicated telephone line for staff to use to 'report anything that could endanger the safety of an aircraft'.

The Civil Aviation Authority is addressing similar issues at other UK regional airports.

Safety recommendations were also made to the helicopter operator to help avoid similar oil leaks in the future.