Bell 206BII N90307

Summary

On 24 August 2000 at about 01:00 local time, a Bell 206BII registered N90307 was involved in an accident near Newhalem, Washington, 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

24 August 2000 at 01:00

Classification

Accident

Location

Newhalem, Washington, United States

Coordinates

48.5891, -122.1290

Aircraft

Bell 206BII

Registration

N90307

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Route

Brewster → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

SEA00LA197

Nobody was injured.

Debonding between the elastomeric material and the center plate of the transmission isolation mount.

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

Read the full NTSB narrative

The pilot reported that after landing the helicopter and reducing the engine to idle power, he heard a 'snap' or 'click' above and behind him. The main rotor immediately pitched back and to the left. This violent gyration resulted in the toe of the skids to lift off the ground and the helicopter moved backwards with each pitch up. The pilot shut the engine down. The main rotors windmilled to a stop and the mast came to rest back and to the left about 30 degrees off of vertical. Inspection of the helicopter found that the pylon isolation mount failed. Examination of the mount found that the failure occurred over a long period of time and was probably due to inadequate surface preparation of the center plate to the elastomeric blocks, which resulted in the debonding of the material and allowing the center plate more movement than normal.

Quoted verbatim from the NTSB record.