The student was receiving training in forced landing procedures. The first three exercises were completed without incident. At the end of the fourth approach to the selected paddock, the student applied full power and initiated a climb, intending to return to 3000 feet for a further exercise. However, when the aircraft had reached about 1700 feet, the engine lost power. The instructor took control, but was unable to gain any response from the engine. The aircraft was landed in a paddock, and collided with a fence some 200 metres from the point of touchdown. Examination of the aircraft revealed that one fuel tank was empty, while the other tank contained about 7 litres of usable fuel. The engine had lost power when the fuel in one tank was exhausted, and air evidently entered the system, preventing normal engine response when the instructor selected the opposite tank. No dipstick had been available and the instructor, who did not rely on the aircraft fuel gauges, had made an erroneous visual assessment of the fuel quantity prior to DEPARTURE. The aircraft had flown for more than 5 hours since the last refuelling.
