AIR accident investigators today began examining the twisted wreckage of the police helicopter.

The stricken aircraft arrived at Farnborough, near Aldershot, last night ahead of an examination which is expected to take months to complete.

Several members of the Air Accidents Investigation Branch (AAIB) had travelled north to the scene of the tragedy at the weekend but a full scale probe was delayed until salvage operators successfully winched the helicopter clear of the Clutha bar.

The delicate operation was completed by lunchtime on Monday.

Today, almost 120 agonising hours after nine people lost their lives - including the civilian pilot and two police officers - investigators began their forensic examination.

They are expected to spend months painstakingly searching for an answer to the one question asked by many: "What caused the helicopter to crash?"

From the twisted metal of the damaged fuselage to the rotor blades, including the gear box and controls from the onboard computer software to the micro systems - every inch of the aircraft will be pored over.

Under EU safety laws, Britain's top aviation specialists will be joined in their task by accident investigators from Germany and France. They will join advisors from the European Aviation Safety Agency and the UK Civil Aviation Authority.

There seems little doubt that working as a team the answer will be found, even though the crash is said to be one of the most complex in UK aviation history.

Officials have stressed there will be no quick answers. A helicopter accident in London which happened in January is still being probed.

If investigators discover any possible defects before their investigation ends they will release a special bulletin.

The AAIB is part of the London-based Department of Transport .

One official said: "Obviously the focus was to get people up there and to make the crash scene safe.

"Now that we have the helicopter at Farnborough, we can fully investigate the cause of this terrible accident. Everything will be looked at in detail."

Investigators have already revealed that the aircraft did not have an onboard black box or flight data recorder.

They have obtained recorded radio information, while it might be possible for them to download "non volatile memory" from micro chips used in the digital electronic control systems which managed the aircraft's engines.

It will now be left to aviation experts 340 miles away in Hampshire to find an explanation for a tragedy.

gordon.thomson@ eveningtimes.co.uk