What happened
On July 18, 2005, a Socata TB-10 aircraft, registration EC-FSP, was performing a solo training flight from Salamanca Airport. Shortly after takeoff, while climbing through approximately 2,800 feet, the pilot detected the smell of smoke and initiated a right turn. As the aircraft reached 3,200 feet, the pilot experienced a gradual loss of power that quickly transitioned into a total engine failure.
In response to the emergency, the pilot directed the aircraft toward a nearby field and executed an emergency landing in a recently harvested wheat field. During the landing, the nose gear collapsed and the propeller struck the ground, resulting in major damage to the aircraft's forward fuselage, engine cowling, and landing gear. The pilot sustained no injuries, though they had been exposed to smoke fumes within the cockpit.
The investigation
The investigation focused on the cause of the engine failure and the source of the smoke. Post-accident inspections of the engine compartment revealed that the left lower side of the engine cowling had been perforated by intense heat or fire, creating a 30 cm hole. Investigators found that a bundle of electrical wires had melted and the engine firewall was deformed.
Upon examining the exhaust system, investigators discovered that the clamp on the left front exhaust pipe had become loose, causing the pipe to detach from its position in the muffler. This detachment allowed hot exhaust gases to be directed against the interior of the engine cowling. The investigation also determined that the engine likely stopped because the detachment of the manifold caused hot gases to be ingested into the engine intake, potentially clogging the air filter. Furthermore, the investigation found that smoke entered the cockpit through the external air scoop due to the heat-induced perforation of the cowling and insulation blanket.
Findings
- The primary cause of the engine failure was the detachment of the left front exhaust manifold pipe.
- The detachment was likely caused by the deformation of the clamp's flexible flange during a previous maintenance session, which weakened the attachment.
- The engine stoppage was likely caused by the ingestion of hot gases from the exhaust system into the engine intake.
- The presence of smoke in the cockpit was due to the heat-induced perforation of the engine cowling and the insulation blanket, allowing fumes to enter via the external air scoop.
- Maintenance records indicated the clamp had been re-tightened during a 50-hour inspection only weeks prior to the accident, but the assembly process was found to be complex and prone to error.
Safety action
- REC 08/06: It is recommended that maintenance technicians be made aware of the critical importance of carefully assembling the clamps of the TB-10 exhaust manifold pipes to ensure they are securely fastened and to prevent detachment during flight.