AN AIR accident investigation was under way last night after five passengers and two pilots luckily escaped injury when their helicopter was involved in a collision as it came in to land on a gas platform 50 miles off Yarmouth.

AN AIR accident investigation was under way last night after five passengers and two pilots luckily escaped injury when their helicopter was involved in a collision as it came in to land on a gas platform 50 miles off Yarmouth.

The CHC Scotia-operated helicopter's tail rotors struck a crane on the Perenco-owned Leman Alpha platform at about 5.30pm on Sunday, but the pilot was able to land safely despite damage to the aircraft.

The accident represents the most significant incident involving a helicopter in the southern North Sea since 11 men were killed in a crash involving a Sikorsy S76 helicopter in 2002.

John Sewell, operations manager at Perenco's Yarmouth base, said yesterday: “The helicopter was able to land and no one was injured and the people were still OK this morning.”

He confirmed the tail rotors had hit the crane but said it was “far too early to speculate on the cause of the incident”. The weather had not been bad at the time.

Mr Sewell said: “It is the first such incident Perenco has been involved in since we started operations in the southern North Sea four and a half years ago.”

The passengers were contractors who had been doing maintenance work on unmanned installations and were being flown back to their base platform for the night. The helicopter is normally based on the platform

As an investigation by the Department for Transport's air accidents investigation branch (AAIB) got under way, all those involved were marooned on the platform as helicopter flights were grounded by yesterday's storm.

At this stage, CHC Scotia has taken no action to ground other helicopters of the same type pending the outcome of the investigation.

Mr Sewell said the helicopter involved was checked by its crew on a daily basis and flew into Humberside for weekly maintenance checks.

A spokesman for CHC confirmed that an AS365N helicopter sustained minor damage as it landed on the platform.

The aircraft was undertaking routine shuttle operations in the Leman Field.

He said: “As a matter of routine, CHC has launched an internal investigation into the circumstances of the incident and all relevant regulatory authorities have been informed.”

A spokesman for the AAIB confirmed it had begun investigating the incident by correspondence.