What happened
On 14 July 2009, a Jodel D112, registration G-BEZZ, was conducting a training flight at City Airport (Manchester Barton). While the aircraft was on the downwind leg of the circuit following a one-hour flight, the pilot noticed smoke entering the cockpit accompanied by a distinct smell of burning wood.
Upon inspection, the crew discovered a hole, roughly 30 mm in diameter, located between and just behind the rudder pedals. The edges of this hole were visibly glowing and emitting sparks into the cockpit area. The pilot immediately issued a MAYDAY call and performed an urgent landing. The airfield's Fire and Rescue Service responded to the scene. By the time the aircraft had finished its ground roll, the glowing around the hole had stopped, and the amount of smoke produced during the final approach had decreased.
The investigation
The investigation focused on the source of the heat and smoke. It was determined that the aircraft's exhaust system had been previously modified to reduce engine noise, as approved by the Light Aircraft Association (LAA). While the original configuration used four stub pipes exhausting below the cowling, the modified version had been altered to improve silencing.
An inspection of the modified exhaust system revealed that the configuration had allowed hot gases to strike the lower fuselage. This thermal impact caused the formation of a hole in the cockpit floor and damage to a stiffening rib.
Findings
- The primary cause of the incident was the modified exhaust system allowing hot gases to impermit onto the lower fuselage.
- This heat exposure resulted in a burn-through of the cockpit floor and damage to the aircraft's internal structure.
- The modification intended to silence the engine inadvertently created a path for exhaust gases to impinge on the airframe.