What happened
On September 15, 2010, a Cessna T207A, registration PR-JTA, was operating a flight from Caima to Pista Nações Unidas, Brazil, transporting a pilot, a passenger, and cargo for a mining company. Approximately 30 minutes after takeoff, while cruising at 6,500 feet, the pilot noticed abnormal noises, dark smoke emanating from the right side of the engine, and a significant loss of power.
Despite attempting to switch fuel tanks, the power loss persisted. Seeking a safe landing site, the pilot identified a strip of land along the Jamanxim River. During the emergency landing, the aircraft struck the ground with enough force to cause the nose gear to collapse and the fuselage to sustain damage. The pilot and passenger were uninjured, though the aircraft suffered severe damage to the propeller, nose gear, and lower fuselage.
The investigation
CENIPA's investigation focused on the Teledyne Continental TSIO-520M engine, which had undergone an overhaul at a maintenance facility (BMA) earlier in 2010. Investigators discovered that the engine overhaul and subsequent test run were performed using incorrect procedures. Specifically, the workshop equipped the turbocharged engine with accessories intended for a naturally aspirated engine and conducted a test run that lasted only 15 minutes, far short of the 90 minutes required by the manufacturer's manual. Furthermore, the operator failed to follow the necessary break-in procedures required to ensure proper piston ring seating.
Findings
- Improper engine maintenance: The overhaul and test run were conducted in disagreement with the Teledyne Continental Motor overhaul manual.
- Incorrect engine configuration: The engine was tested using accessories for a naturally aspirated engine rather than the required turbocharger components.
- Inadequate ring seating: Because the engine did not undergo a proper break-in period, the piston rings failed to seal correctly, leading to compression gas leakage.
- Thermal damage: The resulting high operating temperatures caused the exhaust valve to become brittle, leading to a fracture in the valve stem.
- Mechanical failure: The valve stem fracture caused internal destruction of the piston and intake valve, resulting in the in-flight engine failure.
- Inadequate oversight: Both the maintenance facility and the operator failed to properly supervise the engine's maintenance and break-in requirements.