DR Hank Townsend, at the centre of a growing localisation row, has defended the decision by the Provisional Airport Authority board to appoint him on a three-year contract as its chief executive officer. He said to advertise and seek someone from outside would have created uncertainty at a time when there was a need to maintain public confidence. ''You have to consider where we are on the airport. We are in the middle of commercial negotiations for the major concessions for fuel supply, aircraft catering and aircraft maintenance. ''The Government will also receive comments at the end of the month from the Airport Consultative Committee and the Legislative Council over the Airport Bill. We have to keep the momentum going.'' Dr Townsend, who takes up his full-time position tomorrow, has been the authority's caretaker chief executive on a 12-month secondment from International Bechtel, the US construction giant. Before that he had been working on the airport project for four years, first in 1989 as a consultant to the Government on the port and airport development study. In the following year he became the consultant project manager on the airport core programme. In an attempt to defuse the political dispute, particularly with the United Democrats of Hong Kong, Dr Townsend re-affirmed the authority's continued support for localisation wherever possible and said the body had ''done an excellent job recruiting locally''. ''Albert Chan Wai-yip [the Democrats' infrastructure spokesman] and I have often talked about localisation and open advertising. And I would like to maintain a good relationship.'' But he added there were times when expatriates and consultants were needed because ''that's the way big business is''. He also said there were particular difficulties with international recruitment which made it an uncertain, lengthy and time-consuming process.