HONGKONG could buy more crime-fighting Black Hawk helicopters if the territory was hit by civil unrest or lawlessness, it was claimed yesterday as two of the aircraft - costing $100 million each - were commissioned into the Royal Hongkong Auxiliary Air Force (RHKAAF). The Sikorsky S70s officially introduced into the RHKAAF fleet will be used mainly by police for duties including border patrols and special operations currently undertaken by Royal Air Force Wessex helicopters stationed at Sek Kong. They will also be available to assist in some anti-smuggling raids. The twin-engined helicopters were officially commissioned by Acting Commissioner of Police Mr John Thorpe at the Police Tactical Unit headquarters in Fanling. One security source said the Government could add more of the helicopters to the 10-strong fleet of the RHKAAF, which is to be replaced by the Government Flying Services at the end of the month. ''The gradual withdrawal of the RAF will mean that the territory will have an even greater reliance on the Government Flying Services in the run-up to 1997,'' the source said. ''Black Hawks have been picked to do jobs previously carried out by the RAF and if there is a need for more of the aircraft in the future, then the police, Security Branch and the Government Flying Services would certainly ask for them. ''The two we have now will be able to cope with general internal security roles and I think there would only be a need for more if the situation considerably worsened within Hongkong and on the border.'' Based in Sek Kong, the helicopters will be able to carry about double the number of men to trouble spots than the RAF Wessex. Chief Inspector Mark Dyson of the Police Tactical Unit said: ''We are hoping to get 20 men at a lift inside the helicopter. ''We would use them in situations such as a disturbance in a Vietnamese detention centre on an outlying island. We would be able to move a lot of people very quickly to that disturbance. ''They could be used if there was an internal security situation involving high-rise buildings and we would be able to put men on top of the building. Generally it increases our capability of moving a lot of men very quickly. ''With two waves, each helicopter flying twice, we should be able to move half a company which is 80 men and that is the major benefit to us.'' The RHKAAF's eight existing Sikorsky S76s are used to ferry VIPs, around the territory and are not equipped to cope with the police's demands.