The DC-8 approached Changi runway 20R following a flight from Yokota. In heavy rain, the first officer, who was pilot flying, could not see the runway lights clearly up to about 200 feet AGL. He continued the approach. Then he felt that the captain was in control and so he let go of the controls but he did not attempt to inform the captain as to whether he was letting him have the controls or he wished to retain the control of the aircraft. The aircraft floated for about 1,300 m before it was put down by the captain. The landing distance available of runway 20R was 3,260 m. When the aircraft touched down, only about 1,500 m of the runway remained available. This was not enough to prevent a runway overrun. The aircraft exited and came to rest about 300 m from the end of the runway. The crew had earlier ascertained from the Runway Analysis Manual that the aircraft’s landing weight was within limit for landing on the runway, but had not determined the landing distance required (2,560 m) from the flight manual. SIGNIFICANT FACTORS: 1 The FO, the pilot flying the approach and landing, did not elect to go around even though he did not have the runway lights and approach lights in sight at 300 feet above ground. 2 The PIC could have taken over control from the FO when the latter still could not see the approach lights and runway lights at 300 feet above ground. 3 The crew landed long by about 1,300 metres on the runway. 4 The crew had not made a determination of the landing distance required for the landing on Runway 20R. They had just verified using the Runway Analysis Manual that the aircraft landing weight was within limit for the landing.