Speeding engine led helicopter to ditch
An engine on a Government Flying Services helicopter that ditched in the Shing Mun Reservoir last month failed because an engine was turning too fast, according to a preliminary accident investigation report released yesterday.
'The overspeed caused an automatic shutdown of the engine. The reason for the overspeed is under investigation,' the Civil Aviation Department report said.
An overspeed occurs when an engine is allowed or forced to run at a number of revolutions per minute beyond its design limit. The problem hit the aircraft's No 2 engine.
The nine-year-old helicopter was picking up water from the reservoir to water-bomb a hill fire in Tai Mo Shan Country Park when it was forced to ditch on December 27.
The four-page report said that just after the bucket left the reservoir's surface on its fifth water pickup, 'the helicopter was rotated to gain forward speed at 129 feet but the pilot noticed that the helicopter suddenly yawed [swerved off course] and the crew members heard an engine-winding-down sound'. The three-man flight crew noted warnings with the codes 'ALARM', 'PWR 2' and 'OEI HI' on the instrument panel.
The pilot saw that the No2 engine's gas generator rotation speed was winding down to 30 per cent and the engine automatically shut down, the report said.
'The captain decided to ditch the helicopter and called 'power loss, ditching',' it said.
He told the co-pilot to deploy the emergency floats, and the water load was released before the pilot jettisoned the bucket.
The helicopter ditched under control near the reservoir's Pineapple Dam, and was kept afloat by the emergency floats. No one was hurt.
'The investigation team is investigating the cause of automatic shutdown of the No2 engine of the helicopter just before the accident,' a spokeswoman said.
It was the second accident involving a helicopter last year. On July 3, two pilots and 11 passengers were rescued after their Macau-bound helicopter had to ditch in Victoria Harbour after take-off from the Shun Tak Centre helipad.