After conducting general flying for about 45 minutes the occupants returned to conduct circuit practice. During take-off after the third stop-and-go landing, an engine power loss occurred. The pilot lowered the nose of the aircraft rapidly but was unable to prevent a collision with the ground and a barbed wire fence. No positive cause for the engine failure was established, however the method of restraining the fuel lines to the aircraft structure was not in accordance with normal engineering practice, and could have restricted fuel flow to the engine. The pilot involved in this accident adhered to a directive issued by the industrial organisation of which he is a member and did not provide any information to assist in the investigation.