On February 20, 1993, a Piper PA-23-160 (registration N4229P) operated by Hif, Inc. was involved in an aviation accident near Cannonball, ND. Investigators recorded the probable cause as: Blockage of the left engine inlet air filter by snow. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot performed a gear-up landing on a river bed after the left engine lost power at 1,000 ft AGL. Post-accident inspection revealed the left engine inlet air filter was blocked by snow, and the right engine filter was also contaminated with snow.
Incident Summary
The pilot reported that while in cruise flight at an altitude of 1,000 feet above ground level, the left engine experienced a loss of power. The pilot observed black smoke emanating from the exhaust and subsequently feathered the propeller. Unable to maintain altitude and believing a return to an airport was not possible, the pilot executed a gear-up landing on a river bed.
Post-Accident Inspection
Examination of the aircraft after the incident disclosed that the left engine's inlet air filter was obstructed by snow. Additionally, the right engine's air filter was found to be contaminated with snow. An inspection of the spark plugs indicated that the engine had been operating with a rich fuel-air mixture.
Probable cause
Blockage of the left engine inlet air filter by snow.