A preliminary report on the August 26 crash of a Government Flying Service helicopter on Lantau Island has been released.

It says the flight was conducted under Special Visual Flight Rules, which require the pilot to remain clear of cloud and in visual contact with the ground.

At the time of the accident the weather at HK International Airport (the cloud base was around 1,200 feet and visibility was 10km) was within Government Flying Service limits for single pilot operations at night.

There was no indication of any aircraft system failures during the flight and no emergency call was made by the crew. Neither Air Traffic Control nor the Government Flying Service received any distress call.

Wreckage showed substantial damage to the main rotor blades within the first few metres of the initial impact.

At the point of the second impact there was much debris from the tail of the helicopter, suggesting a touchdown in a nose-high attitude.

The Civil Aviation Department said the preliminary report contains facts relating to the accident as determined up to the time of issue and must be regarded as tentative.

More in-depth investigation and analysis work remain to be done before a conclusion can be drawn on what caused the accident. The final report is expected to be completed within one year.