Hiller UH 12E N36MV

Summary

On 9 December 2013 at about 14:30 local time, a Hiller UH 12E registered N36MV, operated by Jeff Streeter Motor Sports Inc, was involved in an accident near Chowchilla, California, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

9 December 2013 at 14:30

Classification

Accident

Location

Chowchilla, California, United States

Coordinates

37.0981, -120.1108

Aircraft

Hiller UH 12E

Registration

N36MV

Category

Helicopter

Year built

1978

Engines

1

Operator

Jeff Streeter Motor Sports Inc

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Chowchilla → Chowchilla

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR14LA062

Nobody was injured.

The failure of the torsional drive coupling, which resulted in a loss of drive to the main rotor system during low-altitude flight.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The pilot, who also owned the helicopter, reported that he was performing frost control operations over a citrus grove at low altitude when the helicopter's engine began to overspeed with an accompanying decrease in rotor speed. He initiated an autorotation, and the helicopter subsequently landed hard in an adjoining orchard. The pilot removed the helicopter from the accident site immediately following the accident and began disassembling it and sending components out for repair before it was examined. During the subsequent examination of the helicopter, both the elastomeric ring and lower drive lugs (engine side) of the main transmission torsional drive coupling were found sheared off, which would have resulted in the loss of drive to the main rotor system described by the pilot. The pilot did not make the torsional drive coupling available for followup examination and reported that he had misplaced the airplane's maintenance logbooks. The torsional drive coupling incorporated an internal set of lugs designed to provide positive drive to the transmission if the elastomeric portion of the coupling failed. The lugs had sheared off, which indicated that the elastomeric coupling had failed before the accident flight. The coupling had a finite service life but, because no maintenance records were provided for examination, it could not be determined if it was within its life limit at the time of the accident. Almost 4 years before the accident flight, the helicopter had been involved in another accident, which destroyed the main rotor blades. The pilot could not provide evidence that the coupling was replaced after that accident, and, without access to the airplane's maintenance logbooks, it could not be determined if a routine inspection of the coupling had been performed. It is possible that the coupling sustained damage during the original accident, which resulted in its ultimate failure.

Quoted verbatim from the NTSB record.