What happened
On 17 June 2014, a Socata TB10 Tobago, registration G-POPI, departed Guernsey Airport for a private flight to Seething Airfield. During the initial climb to 1,500 ft, the pilot and passenger noticed a faint burning smell, which was quickly followed by a massive influx of smoke entering the cabin through the pilot's footwell.
As the smoke became thick and choking, the pilot declared an emergency and turned back toward the airport. Fearing an uncontrollable engine fire and facing near-zero visibility, the pilot shut down the engine. Due to the lack of visual references and the inability to see the instruments, the pilot attempted to maintain a steady glidepath. The aircraft struck a disused, overgrown greenhouse approximately 0.5 nm short of the runway. The impact resulted in one minor injury to the pilot and one serious injury to the passenger, while the aircraft was destroyed.
The investigation
Investigators examined the wreckage and identified significant heat damage on the lower left side of the glass-fibre engine cowling and the forward fuselage. While the engine firewall remained intact, a seal around the nosewheel steering linkage had been severely heat-affected, which allowed smoke to penetrate the cockpit.
Technical analysis revealed that the exhaust downpipe for the No 4 engine cylinder had fractured at the clamp where it meets the muffler. This fracture allowed hot exhaust gases to escape into the cowling area. The investigation noted that the location of the crack, situated within the clamp, made it nearly impossible to detect during standard inspections without dismantling the component.