ACAS warning involving a The Boeing Company 747-438, VH-OJG, Bangkok, on 21 April 1993

The pilot reported that at 11,000 feet on climb out of Bangkok the Traffic Collision Avoidance System (TCAS) gave a traffic alert message immediately followed by a 'climb, increase climb' warning. Evasive action was taken. The initial navigation display indicated traffic at a range of one half to one nautical mile ahead in the 12 o'clock position, 300 feet above and in level flight. Air Traffic Control reported no traffic in the area. Visibility was about 10 kilometres in haze and no aircraft was sighted in that position. Subsequent investigation revealed no defect with TCAS equipment.