On May 11, 1984, a Hiller UH-12E (registration N46RJ) was involved in an aviation accident near Cedar Hill, TX. Investigators recorded the probable cause as: Engine failure due to oil starvation because the drain valve was not closed after servicing, allowing oil to be pumped overboard during engine start and takeoff. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During its first night flight following an oil change and annual inspection, a helicopter suffered a total power plant failure due to oil starvation. The drain valve had been left open, causing oil to be pumped overboard. The helicopter struck a building during autorotation.
Accident Overview
A helicopter experienced a complete power plant failure during its initial night flight after receiving an oil change and annual inspection. The pilot performed an autorotation, but the helicopter struck a building before coming to rest.
Investigation Findings
An inspection of the wreckage revealed that the engine failure resulted from oil starvation. Further investigation determined that the oil system had been adequately serviced; however, the drain valve had not been closed. Upon engine start and subsequent takeoff, the oil was pumped overboard, leading to the loss of engine power.
Sequence of Events
The helicopter underwent an oil change and annual inspection.
During the first flight after maintenance, which occurred at night, the engine lost all power.
The pilot initiated an autorotation, but the aircraft collided with a building during the descent.
Post-accident examination found the oil drain valve in the open position, confirming that the oil loss occurred during engine operation.
Probable cause
Engine failure due to oil starvation because the drain valve was not closed after servicing, allowing oil to be pumped overboard during engine start and takeoff.