Hiller UH12D N100HH

Summary

On 25 August 1991 at about 02:50 local time, a Hiller UH12D registered N100HH, operated by Pathfinder Technology Inc., was involved in an accident near Sparks, Nevada, 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

25 August 1991 at 02:50

Classification

Accident

Location

Sparks, Nevada, United States

Coordinates

39.5999, -119.6906

Aircraft

Hiller UH12D

Registration

N100HH

Category

Helicopter

Engines

1

Operator

Pathfinder Technology Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Reno → Stead

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

LAX91LA369

Nobody was injured.

THE ENCOUNTER WITH ROUGH, UNSUITABLE TERRAIN DURING A PRECAUTIONARY LANDING. CONTRIBUTING TO THE ACCIDENT WAS THE PILOT'S DECISION TO MAKE AN AUTOROTATION AFTER ENCOUNTERING AN AIRFRAME VIBRATION.

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

Read the full NTSB narrative

THE CERTIFICATED PRIVATE HELICOPTER PILOT, THE SOLE OCCUPANT, WAS ON A LOCAL AREA FLIGHT WHEN A STRONG, MEDIUM TO HIGH FREQUENCY VIBRATION DEVELOPED IN THE TAIL SECTION OF HIS HELICOPTER. THE PILOT ELECTED TO MAKE A PRECAUTIONARY LANDING IN AN OPEN DIRT AREA, AND EXECUTED AN AUTOROTATION. AFTER TOUCHDOWN THE HELICOPTER SLID ON ROUGH, ROCKY TERRAIN, CAUSING THE MAIN ROTOR BLADES TO CONTACT THE TAIL BOOM. THREE FEET OF THE TAIL BOOM INCLUDING THE TAIL ROTOR GEAR BOX AND BLADES, AND THE TAIL ROTOR DRIVE SHAFT WERE SEVERED. AN EXAMINATION OF THE TAIL ROTOR DRIVE SHAFT AT THE POSITION WHERE A SUPPORT BEARING IS MOUNTED, REVEALED SIGNS OF HEAT AND WEAR. DURING THE IMPACT SEQUENCE, THE DRIVE SHAFT SUPPORT BEARING DEPARTED THE HELICOPTER AND WAS NOT RECOVERED.

Quoted verbatim from the NTSB record.