ROYAL Air Force helicopters based in Hong Kong have been grounded after a fatal crash in Britain, but risks will be taken to fly emergency missions, the Commander British Forces, Major-General John Foley, said yesterday. Orders from the Ministry of Defence in London have banned non-operational use of all 60 Wessex helicopters used by the RAF around the world, including the eight flown by 28 Squadron based at Sek Kong. Investigations are continuing into the cause of last Friday's crash in Snowdonia, north Wales, in which three teenage cadets were killed and four others injured. Preliminary reports indicate the drive shaft to the tail rotor failed, causing loss of directional control. Witnesses said they saw the tail rotor stop before the helicopter spun into a lake, sinking almost immediately. Checks are being made to see if similar faults exist on the 29-year-old Wessexes at Sek Kong but they will be available for emergency use, said General Foley and the officer commanding 28 Squadron, Squadron Leader Steve Murkin. The helicopters are used in air-sea rescues, fire-fighting and emergency evacuation as back-up for the Government Flying Services (GFS), in addition to their military role. ''For emergency or life-saving purposes our Wessexes will fly,'' General Foley said. ''There is a risk but it is thought to be an acceptable risk which I wish to take. I'm quite certain that Squadron Leader Murkin would have balanced the risks and he seems very happy to fly under the circumstances. ''In my judgment I would support missions with the potential of saving life.'' Non-urgent military operations, such as moving troops by air when they could go by road, have been banned, as have training flights and moving non-militarypersonnel. Engineers at Sek Kong are expected to complete their tests on the drive shafts of the helicopters today and will forward the results to the Ministry of Defence. It is expected that the inquiry will be finished tomorrow and a verdict on whether the Wessexes are safe to fly will be made then. Squadron Leader Murkin briefed his air crews on the crash in Wales and the action being taken in Hong Kong, but said he was convinced that the Wessexes, which can carry 12 passengers and two crew, were safe. ''An accident of this type is very unusual, it sounds like a one-off catastrophic failure which you can do nothing about,'' he said. ''The drive shaft is not something we would normally worry too much about. All the components are given a life, and are replaced when that time is up. ''The numbers on the side may say they are old but we keep a very close eye on how the equipment bears up under strain and replace everything when necessary.'' He said the crew involved in the Snowdonia crash had particular problems because they were flying at a low altitude and low speed which gave them no opportunity to take corrective action.