What happened
The flight proceeded to the destination at 6,000 feet, remaining above the cloud layer during transit. Upon nearing the airport, the pilot contacted the destination on UNICOM frequency and received advisory information indicating low ground fog and very poor visibility conditions. Despite this report, the pilot did not seek further clarification of the weather situation before initiating an NDB approach.
The aircraft entered clouds at 4,000 feet during the descent. Structural icing began to accumulate on the airframe while in instrument meteorological conditions. Although the pilot briefly sighted runway lights, visual contact was lost when maneuvering to adjust the course for the missed approach procedure.
Due to the accumulation of ice, the aircraft became unable to climb above 3,800 feet and subsequently could not maintain altitude as the icing continued. The pilot was unable to arrest the descent. However, upon regaining visual contact with the ground, the pilot maneuvered the aircraft to execute a forced landing in an open field.
The investigation
Post-accident analysis confirmed that structural icing occurred during the approach phase. The weather data indicated that the freezing level was forecast between 3,000 and 4,000 feet, placing the aircraft directly within the icing zone. The pilot reported that conditions at the destination were above approach minimums at the time of landing, despite the earlier advisory of poor visibility.
Findings
The primary factor contributing to the accident was structural icing which degraded aircraft performance. Contributing factors included the decision to continue the approach into known icing conditions and the failure to maintain altitude during the missed approach due to ice accretion.