DISCIPLINARY action will be taken against two Royal Hongkong Auxiliary Air Force pilots who crashed their twin engine plane into the sea near Tolo Harbour. A four-man RHKAAF investigation team set up after the December 15 accident has concluded human error was to blame. The pilots, both cadets, survived the crash, although the 20-year-old Norman Islander aircraft they were flying has been written off. The aircraft had been due to be taken out of service. Investigation team member, Squadron Leader Graeme McIntosh, refused to disclose what sort of action would be taken against cadet pilots Mr Alan Wong Kwok-lun, 27, and Mr Kwan Kit-wah, 28. But he cited a lack of self-discipline as the cause of the accident. The men had been on a routine training flight to practise steep turns and stalls when they were forced to ditch the plane after both engines failed. Mr McKintosh said the pilots had been flying at 750 metres in low temperatures, but failed to follow the proper procedures to prevent the carburettor from freezing up. ''They should have directed exhaust gases back through the intake system to prevent the build up of ice in the carburettor,'' he said. ''If not enough air gets to the engine, it will stall.'' Mr McKintosh said it was part of the cadets' basic training to be ''made aware'' of the procedure to prevent carburettors from freezing and triggering engine failure. He said the procedure was useful in local flying conditions during only six weeks of the year when the temperature dropped to about six degrees. ''Throughout most of the year, conditions do not warrant carburettor heating and maybe they just forgot,'' he said. He said that although it may have been warm on the ground, the temperature could have dropped substantially by the time the aircraft had climbed to 750 metres. ''But the temperature was indicated on the control panels and they should have seen that,'' he said. Mr Mckintosh defended the training provided to RHKAAF cadets and said there was no need for a review of the system. ''We can teach the procedures on the ground but once airborne it is really up to the individual to do what he should be doing.'' Other aircraft used by cadet pilots, such as the Slingsby, had fuel injection engines which did not have the same problem with carburettor ice build up at low temperatures, he added. Both cadets were qualified as private pilots and had about 400 hours of flying time. Mr Kwan, who was acting as co-pilot, also had a licence to fly a fixed-wing aircraft.