The pilot-under-training was undergoing type familiarisation. After some time in the training area, the pilot returned for circuit work. After one normal circuit and landing, the pilot was attempting a glide approach. The instructor reported that although the aircraft was slightly low, everything else appeared normal. At about 300 feet above the ground, the aircraft started to sink, well below the desired glide path. The pilot did not react immediately, so the instructor commanded a go-around, at the same time reaching for the controls himself. The engine responded with full power but the aircraft continued to sink and landed heavily on the mainwheels, approximately 450 metres short of the runway threshold. It bounced onto the nosewheel and became airborne again. The instructor took over full control and went around, unaware that the noseleg had broken off just above the fork. On the subsequent approach, the instructor saw a wheel on the ground, and was advised by another pilot that it was his nosewheel. The instructor later carried out a landing on a grass flight strip. During the landing roll, the broken noseleg dug in and the aircraft tilted onto its nose before falling back onto the mainwheels. The wind was reported as generally straight down the runway at 10 to 20 knots, with a slight sea breeze component and a small amount of sink on final approach.