A SPECIALIST aircraft maintenance firm has favoured the Tseung Kwan O Industrial Estate instead of a site at the new Chek Lap Kok airport as the centre for its operations in the future. Andrew Herdman, managing director at Hong Kong Aircraft Engineering Co Ltd, said his company would move most of its existing operations at Kai Tak to Tseung Kwan by mid-1996. An engine test cell, various general workshops and support activities for the servicing of smaller aircraft components, would be located at the new four-hectare site at Tseung Kwan O. He said the firm had to move from Kai Tak because rents in the area ''will be too high'', once the airport relocates to Chek Lap Kok. The company's only real alternative to moving to Tseung Kwan O was to set up its activities at Chek Lap Kok, he said. But the Hong Kong Industrial Estates' Corporation site was ''competitively priced'' and, in particular, it was a fixed price, he said. At Chek Lap Kok, rentals could be expected to rise with inflation and he was not certain what the initial charges would be. Mr Herdman's company also needs to set up its new maintenance centre in mid-1996, before the Chek Lap Kok airport is completed, to cater for new advances in aeroplane technology. A new generation of passenger aircraft was coming into existence which needed larger maintenance facilities for overhaul work, he said. The new airbus A330 and the Boeing 777 have engines which are nearly twice as powerful as the engines used on Boeing 747s. Engines on a 747 have a 60,000-pound thrust, while those on the A330 and Boeing 777 have a 100,000-pound thrust. Cathay Pacific, which partially owns Hong Kong Aircraft Engineering and is its biggest client, will take delivery of a number A330s this January and of some Boeing 777s in 1996. The maintenance firm is planning to build a larger state-of-the-art engine test cell at Tseung Kwan O to replace its existing building at Kai Tak. Hong Kong Aircraft Engineering is typical of the companies which the Industrial Estates' Corporation hopes to attract to Tseung Kwan O and its other two sites, because it is a high technology company which needs to carry out much of its work in custom-made single-storey buildings. Mr Herdman said the high value-added production activities carried out by his company and encouraged by the Industrial Estates' Corporation were the correct types of operations for the Government to support. ''We cannot turn the whole of Hong Kong over to a glorious service economy without a manufacturing sector. We have to keep moving up the higher value-added activities and move the lower value activities outside Hong Kong,'' he said. ''[The provision of suitable sites for high technology industries is] one of the few areas where the Government has a conscious policy on the industrial sector, because it has recognised the problem of expensive land, which is a deterrent to many firms looking to set up here.'' Although the company had operations in China, Mr Herdman said it had decided to keep its engine overhaul activities there, because engine overhaul work was capital intensive, rather than labour intensive. He said an aircraft engine could cost US$6 million and needed to be worked on by highly trained people, he said. In addition to its engine-testing service, Hong Kong Aircraft Engineering is involved in another type of aircraft maintenance operation in Hong Kong. The firm runs a joint venture with Japanese firm Bridgestone Aircraft Tyres Asia retreading aircraft tyres at Tai Po.