What happened
On March 11, 2010, a Cessna 150J, registration PT-BKU, was performing a local flight instruction session for touch-and-go maneuvers at the Londrina Aerodrome (SBLO) in Paraná, Brazil. The flight involved an instructor and a student pilot. Following the completion of the first traffic pattern, the aircraft experienced a sudden loss of engine power during a go-around maneuver. The instructor took control of the aircraft, executed the engine shutdown procedures, and performed an emergency landing in a nearby soybean field. The aircraft sustained light damage, including a deflated right tire and minor damage to the landing gear wheel pants, but both crew members escaped without injury.
The investigation
The CENIPA investigation focused on identifying the cause of the power loss by examining the engine components, fuel, and environmental conditions. Analysis of the fuel showed no abnormalities. However, inspections of the engine accessories revealed several discrepancies. In the right magneto, investigators found a damaged shaft seal and the presence of oil within the distributor block. Additionally, a bench test of the magneto revealed a failure in the spark of one electrode.
An inspection of the carburetor revealed a loose accelerator pump shaft, worn pump sealing, and signs of oxidation within the bowl. The investigation also considered the meteorological conditions at the time, noting that high humidity and specific temperature/pressure levels were conducive to carburetor icing. The investigation examined three possible hypotheses: oil leakage into the magneto, a failure in the carburetor's fuel delivery during the power increase, or the accumulation of ice in the carburetor after the carburetor heat was turned off during the go-around.
Findings
- Carburetor maintenance issues: The worn and loose accelerator pump seal may have compromised fuel delivery when the pilot advanced the throttle.
- Magneto malfunction: A damaged seal in the right magneto allowed oil to enter the distributor block.
- Environmental factors: Atmospheric conditions were highly favorable for carburetor icing, which may have occurred after the carburetor heat was deactivated during the maneuver.
- Maintenance oversight: The investigation identified potential inadequacies in maintenance supervision and component servicing at the involved maintenance facilities.