STRONG winds from Typhoon Sam were played down by the Observatory yesterday as a significant factor in last Sunday's fatal air crash. The Observatory's acting director, Lam Chiu-ying, said the location of the airport made it more vulnerable than Kai Tak to strong crosswinds. However, the risk of having crosswinds stronger than 25 knots an hour was no higher than 0.1 per cent, said Mr Lam. He declined to disclose the strength of the crosswind at Chek Lap Kok when the plane made its crash-landing, for fear of pre-empting the investigation. But he said: 'Whether a plane should take off or land depends not only on wind speed but also on the height of the clouds and on the visibility.' Mr Lam said that visibility at Chek Lap Kok during the crash was about one to two kilometres. Airport planners, pilots, air traffic controllers, and meteorologists had warned of the risk of turbulence and wind shear when Chek Lap Kok was chosen as the site for the new airport. Initial reports by the Observatory said that there were significant northwesterly crosswinds at Chek Lap Kok. However, there were no reports of wind shear, which can seriously destabilise aircraft. Mr Lam also said there was no need to close the airport when a No 8 typhoon signal is hoisted. 'Many of the world's airports operate normally in conditions as windy as that under our No 8 typhoon signal,' Mr Lam told Commercial Radio. 'In fact, if wind blows parallel to the runway, a plane can actually take off more easily and smoothly,' he said.