What happened
On 6 October 2007, a Cessna 152, registration G-OPJC, was conducting a training flight near St Mary’s Marsh, approximately 4 miles northeast of Gravesend, Kent. The aircraft was occupied by an instructor and a student pilot and had been airborne for approximately fifteen minutes when the instructor experienced a sharp stinging sensation on his right ankle, accompanied by a burning smell and smoke filling the cockpit.
In response to the emergency, the instructor declared a 'MAYDAY' and shut off both magnetos and the fuel supply. The pilot selected a field on St Mary’s Marsh for a forced landing. While the smoke cleared during the descent, the aircraft touched down in the chosen field. During the subsequent ground roll, the aircraft entered a drainage ditch at the edge of the field, causing damage to the nose gear and the forward fuselage. There were no injuries to the two crew members.
The investigation
Investigators examined the aircraft's electrical flap system, which is operated via a selector switch and protected by a 15 Ampere circuit breaker. Although the instructor had selected full flaps for the approach, the flaps failed to deploy. Post-accident inspections revealed that the 'flaps up' switch, located behind the console, had sustained significant heat damage. Laboratory analysis of the switch showed evidence of arcing within the component.
Testing of the 15 Ampere circuit breaker confirmed it was functioning correctly, as it did not trip despite the electrical fault. While the flap position indicator was found to be bent upwards, investigators determined it was unlikely to have contributed to the event, as the selector had not been used in the period leading up to the emergency.
Findings
- The primary cause of the smoke and burning sensation was arcing within the 'flaps up' switch.
- The circuit breaker failed to trip because the current did not exceed its 15 Ampere rating.
- The aircraft's nose gear and forward fuselage sustained damage due to the aircraft striking a drainage ditch during the landing roll.