HONG KONG'S efforts to save disaster-stricken Rwandan refugees will hit new heights tomorrow when a specially chartered aircraft takes off from Kai Tak loaded with vital emergency relief supplies. The mercy flight has taken just a few days to organise in a battle against the clock to save the sick and starving Rwandans. On board the aircraft will be hundreds of boxes of medical equipment and medicine, soap, blankets, and five military Land Rovers capable of transporting essential fresh water to the huge number of refugees who fled Rwanda's bloody civil war. The departure of the Cathay Pacific Boeing 747 cargo aircraft, organised by staff at Medecins Sans Frontieres (MSF) Hong Kong, is being funded from the $8.8 million given by generous local people to the Hong Kong Joint Appeal for Rwanda, and from a government donation. ''This is a chance for Hong Kong people to see their generous response quickly delivered to the people who need it most,'' said Anne Decortis, head of the Hong Kong office of MSF. The plane is scheduled to arrive at Entebbe, Uganda, on Sunday morning. MSF has received assurances from there that the cargo will be flown to Goma, Zaire, by American aid workers and distributed among the refugee camps later the same day. MSF Hong Kong was asked by its Belgium-based headquarters last Friday to try to co-ordinate a mercy flight to aid the global relief effort in Rwanda. Supplies in Europe were running low and MSF had been searching for new sources. Yesterday, delighted staff said they were extremely grateful to Cathay Pacific and everybody who donated supplies, helping to get the flight off the ground so quickly. ''People have bent over backwards for us. We are managing to send this plane for an incredibly small proportion of the money which has been donated to the Joint Appeal,'' said MSF head of communications Fiona MacMahon. The flight alone would normally cost around $2 million, said Cathay. The five military surplus Land Rovers, complete with 200 jerry cans, have been supplied by the British Forces at what MSF described as a ''symbolic'' rate. Forces spokesman Major Paddy Hartigan said the vehicles had been destined for auction, but they had been worked on, painted white, and were in excellent condition for the job ahead. ''The British Forces can't give money but we can use this system of off-loading surplus equipment to help,'' he said. The medical supplies include several hundred boxes of syringes and gloves to be used by MSF clinics operating in Goma, and tablets to combat dysentery. Boxes of soap will prove vital in the fight to improve sanitation and help the increasing number of refugees suffering from dysentery. Peter Sutch, chairman of Cathay Pacific, said the airline was delighted to have made such a contribution to the operation. ''Taking this freighter out of service and mounting a special charter to Entebbe has been an enormous effort involving hundreds of Cathay Pacific staff over a very short period of time, and my thanks go to all involved, particularly the crew of five who will operate in Africa.''