A LIGHT plane from a top American atmospheric research group will arrive on Saturday to start testing turbulence around the Chek Lap Kok airport site. The blue-and-white Kingair - the same model as used by the Government Flying Service (GFS) - will be in Hong Kong until at least November as part of the $118.7 million windshear warning project being conducted by the Hong Kong University of Science and Technology (HKUST). The project with the Royal Observatory will result in a state-of-the-art warning system for pilots landing and taking off at the new airport. Legislators have expressed concern about the safety of the site, which the Royal Observatory admits suffers 30 per cent more thunderstorms that could lead to windshear than Kai Tak. Windshear - a severe change of wind speed near the ground - was blamed for the fatal crash of a CAAC Trident at Kai Tak in 1988. The plane would spend most of its time doing simulated take-offs and landings at Chek Lap Kok, said Dr Brant Foote of the US project partner, the National Centre for Atmospheric Research. About two or three times a week a GFS pilot would fly the plane from Kai Tak, south to Waglan Island, west along the territorial boundary and round Lantau into the Chek Lap Kok descent path, said Dr Foote. This route kept it away from Kai Tak traffic. It would also fly roughly northwest-southeast across the Lantau hills to check turbulence at various heights up to about 8,000 feet, he said. Temperature, humidity, pressure and wind speed would be measured using instruments in the nose cone, body and in canisters hanging from the wings. The figures would be compared with expected turbulence figures. May and June were the most turbulent months according to local pilots, Dr Foote said, but data would be collected throughout the summer typhoon season. Professor Gary Heinke of the HKUST Institute of Environmental Studies said the Environmental Protection Department also expected to get an extra $2.5 million to keep the plane until the end of the year to study air pollution.