On June 16, 1999, a Hiller UH-12C (registration N57CR) was involved in an aviation accident near Delphos, OH. Investigators recorded the probable cause as: A blocked fuel line, from an unknown object, that resulted in fuel starvation, and total loss of engine power. A factor in the accident was the pilot's failure to maintain rotor rpm during the autorotation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter undergoing a post-maintenance test flight experienced a partial power loss and engine surges about 30 minutes into the flight. The pilot executed an autorotation to an open field, resulting in a hard landing. Post-accident examination found no pre-impact failures in the engine or fuel system.
Event Summary
After maintenance was completed to replace an engine, the pilot conducted a test flight. Following the test flight, the pilot paid the bill and departed. Approximately 30 minutes into the subsequent flight, the pilot felt the helicopter shudder and noticed a partial loss of power accompanied by engine surges. The pilot initiated an autorotation, landing in an open field. The landing was characterized as hard.
Post-Accident Examination
No pre-impact failures or malfunctions were identified with the engine or its accessories. After the accident, the helicopter contained approximately 25 gallons of fuel. When power was applied to the auxiliary fuel pump, the pump rotated but did not expel any fuel. Examination of the auxiliary fuel pump revealed no failures or malfunctions. Additionally, no breaks were found in the fuel system. The engine-driven fuel pump and the auxiliary fuel pump share a common fuel filter and plumbing from the fuel tanks.