Synopsis
On 17 June 2014, a Socata TB10 Tobago, registration G-POPI, departed Guernsey Airport for a private flight to Norfolk. While climbing, smoke entered the cabin, rapidly becoming thick and choking. The pilot shut down the engine and turned back toward the airport. The aircraft struck a disused greenhouse approximately 0.5 nm short of the runway, resulting in serious injuries to the passenger and destruction of the aircraft.
History of the Flight
The aircraft had arrived from Seething Airfield earlier that day and was preparing to return. Takeoff and climb on Runway 09 were normal. The pilot climbed straight ahead to 1,500 ft while the passenger took photographs. After leveling off, he turned toward the ORTAC reporting point. While above Fermain Bay, south of St. Peter Port, both occupants noticed a faint burning smell.
Moments later, large quantities of smoke suddenly entered the cabin from the pilot's footwell. The pilot immediately turned left back toward Guernsey Airport and declared an emergency to ATC, intending to land on Runway 27. As he rolled out of the turn, his vision became restricted by smoke. He suspected an uncontrollable engine fire and shut down the engine using the ignition keys, locating them by feel. Concerned about asphyxiation, he was reluctant to open the gull-wing doors due to potential airflow disturbances. He briefly communicated with ATC to correct a misunderstanding about his approach path.
Unable to see outside the cockpit or the instruments, the pilot attempted to maintain a steady glidepath on a straight-ahead track, hoping to reach the airfield. The smoke cleared slightly, and he saw in his peripheral vision that the aircraft was below 100 ft and impact was imminent. Looking up, he saw tree branches and pulled back on the control yoke. Impact occurred shortly after, about 0.5 nm short of the runway.
The aircraft came to rest suspended nose-down and slightly left-wing-low inside a disused, overgrown commercial greenhouse. The pilot sustained an injury above his right eye and asked about his passenger, who reported a back injury. Concerned about fuel leaking from ruptured wing tanks, the pilot told the passenger they must exit immediately. They both left through the pilot's door and were assisted by people on the ground. Both were taken to hospital; the passenger suffered serious injuries to several vertebrae and was airlifted to Norwich for surgery.
Wreckage Examination
A local maintenance organization examined the wreckage and provided a report to the AAIB. Severe burning was found on the lower left side of the glass-fibre engine cowling, along with scorching of the metal forward fuselage structure. The left side of the engine firewall was also scorched; although the firewall remained intact, a seal around the nosewheel steering linkage had been badly heat-affected and likely allowed smoke to enter the cabin.
The No. 4 engine cylinder exhaust downpipe had fractured at the clamp where it joins the exhaust muffler. The other end of the pipe allowed movement, so the fractured end was free to release hot exhaust gases unrestricted into the cowling. The exhaust system and muffler were visually inspected every 50 flying hours or 6 months under the Light Aircraft Maintenance Programme. The condition of the fracture suggested it started as a crack that developed over a considerable period, but its location inside the clamp made it very difficult to detect without dismantling the joint.