What happened
On 11 July 2006, a Cessna 152, registration G-BNDO, was conducting a private cross-country flight from Andrewsfield. Approximately 35 minutes into the flight, while cruising at 1,800 ft, the pilot observed blue smoke emanating from the engine cowling area. This was accompanied by a distinct smell of electrical burning and a bright low-voltage warning light on the instrument panel.
Believing an electrical fire was in progress, the pilot initiated a precautionary landing in a wheat field at Wick Farm, Layer Marney. Following emergency procedures, the pilot kept the Master Switch on to maintain radio and flap functionality during the approach. The aircraft touched down on all three wheels in a level attitude with a 5 kt tailwind. However, as the nose descended following the main gear touchdown, the aircraft struck a large rut in the field. This caused the nose landing gear to collapse and the aircraft to overturn onto its back. There were no injuries to the pilot or the passenger.
The investigation
The investigation examined the aircraft's condition and the mechanical cause of the smoke. While the pilot initially feared a fire, an engineering inspection revealed that the alternator drive belt had failed. This failure caused the blue smoke and the low voltage indication. There was no evidence of an actual fire or oil leaks. The investigation also looked at the ground conditions, noting a rut approximately 12 metres from the touchdown point that led to the gear collapse and subsequent overturn.
Findings
- The failure of the alternator drive belt was the primary cause of the smoke and the low voltage warning.
- The aircraft overturned because the nose landing gear struck a rut in the field, causing the gear to bend and the aircraft to capsize.