Incident Overview
During the initial climb after takeoff, the aircraft experienced a partial loss of engine power. The pilot selected carburetor heat, but the power level remained too low to sustain altitude. This necessitated a forced landing in rough, wooded terrain.
Investigation Findings
Post-incident examination revealed no discrepancies in the fuel or ignition systems. However, the alternate duct for induction air, which is used when carburetor heat is selected, was found to be almost totally blocked by a mud dauber nest. The normal induction air duct and its filter had sustained impact damage, and conclusive determination of blockage there was not possible.
The aircraft's annual inspection was 5 months overdue at the time of the incident.