THE Civil Aviation Department began investigating yesterday why a New Year's Day incident involving two China Airlines jets at Kai Tak airport was not reported in official department logs. Exact details were not given, but the incident was described as a 'managerial' problem, rather than one of safety. 'There was never any danger of a collision,' a department spokesman said. 'It was something internal that we are looking into,' he said. The spokesman said two jets, one taking off at 7.56 am and the other landing at 8 am, breached local landing and take-off pattern requirements as a result of a mistaken call by air traffic controllers. Further details were not given, except that the incident was not recorded in the day's logs as it should have been.