Incident Overview
During departure, the pilot reported normal taxi and takeoff. However, while preparing to retract the landing gear, a gradual loss of manifold pressure was noticed. The pilot decided to land in a nearby field, which was accomplished without further incident. During the subsequent rollout on the ground, the aircraft struck a ditch, causing the right landing gear to penetrate through the wing surface.
Inspection Findings
Post-incident inspection revealed that the alternate air door had broken free from its mounting. The detached door was ingested into the engine air intake and traveled to the fuel controller, where it obstructed the airflow. This blockage was determined to be the cause of the manifold pressure loss. Notably, the aircraft had undergone its annual inspection only two hours prior to the flight.
Conclusion
The incident resulted from a mechanical failure of the alternate air door shortly after an annual inspection. The pilot's immediate decision to land in a suitable field likely prevented a more critical situation, though the subsequent ground obstacle caused structural damage to the aircraft.