History of the Flight
The pilot completed a pre-flight check, confirming sufficient engine oil, and departed from Andrewsfield on a local cross-country flight. Approximately 35 minutes into the flight at 1,800 ft, the pilot observed blue smoke emanating from the forward section of both sides of the engine cowling. Simultaneously, he detected a strong smell of electrical burning and noted a change in engine noise similar to that during magneto checks. The engine indications appeared normal, but the low voltage warning light was glowing very brightly.
Believing an electrical fire had occurred, the pilot decided to make an immediate precautionary landing in a large wheat field directly ahead. When he closed the throttle to idle, the smoke appeared to stop. He issued a Mayday call to Andrewsfield Radio on 130.55 MHz and continued with the landing. The pilot consulted the emergency checklist for a fire in flight but elected to leave the electrical master switch on to operate the flaps and radio.
The aircraft was established on a stable approach with a 5 kt tailwind. After selecting full flaps, the pilot turned off the master switch and held the aircraft in the flare until the main wheels touched down at approximately 50 kt. As the nose was lowered, the aircraft came to an abrupt halt and turned onto its back. The engine stopped when the propeller struck the ground. The pilot exited through his door and assisted the passenger in vacating the aircraft. Shortly thereafter, two farmers, police, and air ambulance helicopters arrived; both occupants were unhurt.
Damage to Aircraft
The nose landing gear leg was bent back against the fuselage. The fin, rudder, and wings were buckled and distorted. The windscreen was cracked, one propeller blade was bent, the engine was shock loaded, and the alternator drive belt had failed.
Investigation
An engineering investigation found that the alternator drive belt had failed. There was no evidence of a fire. From photographs and comments from an engineer who inspected the aircraft, it was established that the aircraft touched down on all three wheels in a level attitude. The engineer noted a large rut across the field approximately 12 m after the touchdown point, which likely caused the nose landing gear to collapse and the aircraft to turn over. The flaps were found in the retracted position.
A replacement battery was fitted, and the electrical systems operated normally for 15 minutes with no evidence of electrical burning smells. The engine oil level was satisfactory with no indication of leakage. It is believed that the blue smoke and illumination of the low voltage warning light were both caused by the failure of the alternator drive belt.