On April 3, 1987, a Hiller UH-12ET (registration N135HA) was involved in an aviation accident near Big Lake, MN. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft experienced a power failure while maneuvering for landing on a ground support trailer. Due to high trees, an autorotation was executed to an adjacent field. The aircraft rolled over after landing on rough terrain. Investigation found a contaminated fuel system with a white milky substance.
Accident Summary
The aircraft was being maneuvered for a landing on a ground support trailer. During this maneuver, a power failure occurred. Because high trees were present, the pilot executed an autorotation to an adjacent field. The aircraft then touched down on rough and uneven terrain. Upon landing, the aircraft rolled over.
Investigation Findings
The investigation revealed that the fuel system was contaminated. Approximately one gallon of a white milky substance was drained from the fuel sump. All major components of the fuel system, including the fuel lines, filters, and pumps, were contaminated. Investigators were unable to determine the origin of the contamination.