Weather and the lack of experience of a pilot in tailwind conditions may be the causes of the May 1 crash of a helicopter into a parked tour bus in Kowloon City, according to a preliminary report released yesterday. The Civil Aviation Department report said the accident could have been caused by 'the prevailing weather at the time of the accident and the operating experience of the pilot under tailwind conditions'. 'Under the effect of a prevailing wind of east-southeast at 16 knots and controlling the helicopter towards the northwest in a tailwind, the pilot encountered difficulties in stabilising the helicopter during the first approach and performed a go-around,' the report said. The report revealed the pilot attempted a second approach and decided to perform another due to difficulties in stabilising the aircraft. 'As he was making a turn to the right, the helicopter started a spin in a clockwise direction. While the helicopter was spinning, it began to lose altitude and drifted in a northerly direction until it impacted the windscreen of a coach parked in the parking lot,' the report continued. The pilot held a Hong Kong private pilot's licence for helicopters and a valid medical certificate, and had 318 hours of flying experience. The department has recommended that single-engined helicopter operations at Kai Tak should be suspended temporarily, and will continue to collect information to determine the circumstances and causes of the accident. 'More in-depth investigation and analysis work has to be done before a conclusion can be drawn on what caused the accident,' a department spokesman said. The helicopter carrying pilot Ng Shu-keung, 48, and his eight-year-old son smashed into the front of the bus about 100 metres from where it was scheduled to land at the aviation club's helipad in Sung Wong Toi Road. Both were trapped in the helicopter's cabin but were conscious when rescuers arrived. A technician working on the bus suffered slight injuries from flying glass. The front of the bus was badly damaged.