Bell 206B N206KS

Summary

On 30 September 2001 at about 00:23 local time, a Bell 206B registered N206KS was involved in an accident near Hilo, Hawaii, United States. 5 people were on board and 2 had minor injuries. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

30 September 2001 at 00:23

Classification

Accident

Location

Hilo, Hawaii, United States

Coordinates

19.6893, -155.0795

Aircraft

Bell 206B

Registration

N206KS

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Hilo → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX01FA306

2 people had minor injuries.

The failure of the mechanic to secure the No. 8 bearing thrust nut during maintenance work, which resulted in the total failure of the first stage turbine wheel shaft. Also causal was his misjudgment of his height during the flare resulting in a hard landing. A contributing factor was the high vegetation in the forced landing field, which resulted in a hard landing.

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

Read the full NTSB narrative

The pilot made a mayday call, shut off the fuel valve, and performed an autorotation into high grass after the single engine helicopter experienced a loss of engine power shortly after takeoff. The pilot had heard a bang followed by illumination of the engine out warning light, and the engine began smoking. During the terminal phase of the autorotation, the pilot assumed the grass height was 3 feet and flared accordingly; however, the grass was at least 6 feet tall. Post-accident examination of the engine revealed that the No. 1 turbine wheel was missing. The No. 8 bearing thrust nut exhibited a locking indentation and a notch on its inside surface. Additionally, indentations were on the threads of the threaded end of the first stage turbine wheel shaft. These marks suggest that the thrust nut was not fully engaged on the first stage turbine shaft. The location of the notch suggests that the edge of the nut protruded beyond the end of the turbine shaft. There were no indications of contact by the shaft threads on the inner surface of the deformed area to suggest that it had been displaced into a groove on the first stage turbine shaft. Review of the maintenance records and interviews with the mechanic, who performed the most recent maintenance work, revealed that the turbine section had been replaced approximately 30 hours prior to the accident. Due to excessive oil consumption, maintenance personnel removed the turbine and replaced the No. 5 carbon seal approximately 14 hours prior to the accident. The maintenance records indicated that the day before the accident, the sump cover had been removed for trouble shooting oil consumption. Though it is not detailed in the maintenance entry, it is interpreted that the "sump cover" referred to is the No. 8 Bearing sump nut since the thrust nut was loose.

Quoted verbatim from the NTSB record.