On April 26, 1990, a Hiller UH-12B (registration N5306V) was involved in an aviation accident near Sanford, FL. Investigators recorded the probable cause as: The pilot's inability to maintain control of the helicopter during an unexplained loss of engine power, which resulted in a collision with the ground. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A student pilot practicing solo traffic pattern approaches experienced an unexplained engine power loss during the fourth approach, leading to a crash landing.
What happened
The accident occurred while a student pilot was conducting a solo flight intended for practicing traffic pattern approaches. The pilot reported that during the fourth approach of the sequence, the helicopter's engine suddenly lost power. Immediately following this mechanical failure, the aircraft began to yaw to the left.
In response to the emergency, the pilot initiated an autorotation maneuver in an attempt to land safely. However, the helicopter struck the ground with significant force and subsequently rolled over. An operational check of the engine performed after the incident revealed no apparent mechanical reason for the reported loss of power.
The investigation
Investigators examined the helicopter following the accident to determine the cause of the engine failure. A specific focus was placed on the engine's operational status post-impact. The examination did not uncover any obvious mechanical defects or failures that would explain the sudden loss of power during flight.
Probable cause
The pilot's inability to maintain control of the helicopter during an unexplained loss of engine power, which resulted in a collision with the ground.