Bell 204-B N4580Y

Summary

On 16 April 1997 at about 19:50 local time, a Bell 204-B registered N4580Y, operated by U.s. Forest Svc./State of TN., was involved in an accident near Calderwood, Tennessee, United States. One person was on board and nobody was injured. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

16 April 1997 at 19:50

Classification

Accident

Location

Calderwood, Tennessee, United States

Coordinates

35.6601, -84.0891

Aircraft

Bell 204-B

Registration

N4580Y

Category

Helicopter

Engines

1

Operator

U.s. Forest Svc./State of TN.

Operating rule

Part 91: General Aviation

Purpose of flight

Public Use

Phase of flight

Not recorded

Route

Copperhill → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

MIA97TA139

Nobody was injured.

The inadequate maintenance inspection of the helicopter resulting in loss of lubrication from the main drive shaft going undetected until failure of the drive shaft.

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

Read the full NTSB narrative

The main drive failed at the transmission end resulting in loss of transmission drive. The pilot performed a autorotation landing in trees and the helicopter rolled inverted and descended through the trees coming to rest on a river bank. Metallurgical examination showed the main drive shaft teeth had separated at the transmission end due to wear from frictional overheating which is a result of loss of lubrication. The helicopter manufacturer instructions require that the main drive shaft be inspected by a mechanic for loss of lubrication and signs of overheating during a daily inspection before the first flight of each day. The operator did not have records to show that the daily inspection had been performed prior to the accident flight.

Quoted verbatim from the NTSB record.