The pilot had not flown for over four months and planned to sell the aircraft. On the day of the accident, he decided to conduct a check flight before the arrival of a prospective buyer. The aircraft took off into a very light breeze and remained in the circuit area for a short time. It then departed to the east, climbing to about 300 feet. It was then seen to commence a left, level (yawing) turn, both wings seemed to come together at the same time and the aircraft fell in a level attitude to the ground. During the sequence, the engine was heard increasing and decreasing power. It was determined that the left wing spar failed under load at about 1.6 metres from the keel tube. Following this failure, both wing spar tubes failed at the attachment points. No pre-existing fault could be found which could have initiated the left wing spar outboard failure. No other fault was found which could have contributed to the accident. Extensive engineering analysis has shown that at a weight of 160 kilograms, wing spar failure could be expected at about 2.3g. Brochures and other literature on the aircraft claim the airframe will withstand up to 8g.