What happened
On March 16, 2016, an instructor and a student pilot were conducting a training flight in a Cessna 152 at Depułtycze Królewskie Airport (EPCD). The flight curriculum included evaluating the student's response to engine failures through a series of simulated emergency landings. Following the third simulated failure, the crew landed the aircraft on the runway. As the aircraft decelerated, the engine shut down spontaneously. After two unsuccessful attempts to restart the engine, the crew shut down all aircraft systems and manually pushed the aircraft to a parking position to clear the runway. The incident was recorded in the aircraft's technical log.
The investigation
The investigation, conducted by the user's commission, examined the engine's performance and the nature of the preceding flight maneuvers. The analysis focused on the engine's operational state during the series of short, low-power flights used for the training exercises. The investigation looked into the accumulation of carbon deposits and the fuel-to-air ratio during the maneuvers.
Findings
Findings revealed that the preceding flights involved extended periods of low-power operation and gliding. These flight conditions led to the accumulation of carbon deposits on the spark plugs, which weakened the spark intensity. Additionally, the low-power maneuvers caused spark plug fouling due to a rich fuel mixture. Because the flights were short and performed in rapid succession, neither the carbon deposits nor the excess fuel had sufficient time to burn off. While the investigation noted that the ignition timing was not incorrect, the cumulative effect of fouling and deposits eventually caused the engine to fail following the final landing.
Safety action
Following the incident, the spark plugs were replaced and the ignition timing was reset, allowing the aircraft to return to service. The investigating body established several preventive measures for similar training scenarios:
- Simulated engine failures must conclude with a full stop rather than an immediate takeoff.
- If multiple simulations are required, each must be followed by a full stop and taxiing to the runway threshold.
- Before entering the runway for subsequent departures, pilots should perform high-power runs to burn off deposits and dry the spark plugs.