The pilot reported that he had completed a number of flights into and out of Darnley Island during the day. When he was arriving at the island later in the afternoon he found that the wind was calm and elected to land into the west to utilise the uphill slope. He considered the influence of the low sun on his vision and accepted the situation. He retracted the flaps on touchdown and commenced normal braking. After realising that the brakes did not appear to be very effective he applied heavier braking. The aircraft seemed as if it would run off the end of the strip, which had a 50 foot drop at its end. The pilot initiated a ground loop. While the aircraft was sliding sideways the landing gear collapsed. The aircraft came to rest off the side of the strip near the escarpment. The strip length is reported to be 500 m. The performance charts indicate that the strip length required for this landing was of the order of 560 m.