Casualties unknown

1983-05-18: Hiller UH-12E (N4027L) — Thermal, CA

Thermal, CA, US

On May 18, 1983, a Hiller UH-12E (registration N4027L) was involved in an aviation accident near Thermal, CA. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data APIEditorial standards

A helicopter experienced partial power loss during a procedure turn at low altitude, regained power momentarily, then the engine quit. During an autorotative landing, the tail rotor struck the ground, causing loss of control. Investigation revealed fuel pump priming issues.

Accident Summary

A pilot reported that while approximately one-third of the way through a procedure turn at about 60 feet above ground level, the helicopter experienced a partial power loss. The pilot completed the turn, leveled the helicopter, and momentarily regained full power before the engine ceased operating. An autorotative landing to a road was initiated, but upon seeing an approaching truck, the pilot maneuvered back toward the field that had been sprayed. During the landing flare, the tail rotor struck the ground, resulting in the pilot losing control of the helicopter, which came to rest on its right side.

Investigation Findings

During the subsequent investigation, it was found that the auxiliary fuel pump had to be primed before the engine would start. Reportedly, a fuel interruption to the pump could cause it to lose its prime, and if this occurred during flight, fuel starvation would follow. The pilot stated that he had made cyclic turns to maintain positive G-forces on the rotor system rather than using cyclic and pedal turns. A quantity of fuel remained in the helicopter, though the exact amount was not specified.

Pilot Actions

After the engine failure, the pilot began an autorotative descent toward a road but diverted back to the agricultural field when a truck approached. The pilot's use of cyclic turns to maintain rotor RPM during the autorotation was noted. The accident sequence concluded with the tail rotor ground strike and the helicopter rolling onto its side.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X43051. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.