What happened
The flight was underway with a student pilot in the cockpit, conducting training maneuvers within the traffic pattern at an airport. The specific objective of the session involved practicing touch-and-go landings, a common exercise for developing landing skills and engine management awareness.
During one such maneuver, after completing a touchdown and immediately beginning the takeoff roll to become airborne again, the aircraft's engine began to exhibit irregular operation. The pilot reported that the engine ran rough and subsequently lost power. Recognizing the mechanical failure, the student pilot initiated an emergency procedure for a forced landing in a field located directly ahead of the aircraft's flight path.
As the aircraft descended toward the intended landing area, the pilot identified two power lines obstructing the direct approach. To avoid striking these obstacles, the pilot pulled back on the control yoke to climb slightly and clear the wires. This maneuver caused the airspeed to decay rapidly below the critical stall speed. The aircraft stalled and impacted the ground with significant force.
The investigation
Following the accident, investigators conducted a thorough postaccident inspection of the wreckage. The examination focused on the engine components to determine the root cause of the power loss experienced during the climb phase.
The inspection revealed a critical mechanical failure within the engine assembly. Specifically, a fractured exhaust valve was found in the number one cylinder. This fracture likely caused the irregular running and subsequent loss of power that precipitated the emergency situation. The structural integrity of the valve was compromised, preventing proper combustion or exhaust flow for that specific cylinder.
Findings
The sequence of events indicates that the initial engine malfunction forced an unplanned landing in a confined area. The decision to maneuver around the power lines, while understandable, resulted in a loss of airspeed. The stall occurred because the aircraft was operated at an angle of attack and speed combination that exceeded its aerodynamic limits during the low-altitude emergency maneuver.
The mechanical failure of the exhaust valve is identified as the primary factor leading to the engine's inability to sustain power. This failure left the pilot with no option but to execute a forced landing, where the proximity to obstacles dictated the flight path and contributed to the stall condition.