Bell 47G2 N1575

Summary

On 22 March 2001 at about 01:45 local time, a Bell 47G2 registered N1575, operated by Versatile Helicopters Inc., was involved in an accident near Ardmore, Oklahoma, United States. 2 people were 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

22 March 2001 at 01:45

Classification

Accident

Location

Ardmore, Oklahoma, United States

Coordinates

34.1908, -97.1097

Aircraft

Bell 47G2

Registration

N1575

Category

Helicopter

Engines

1

Operator

Versatile Helicopters Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Ardmore → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Night/Dark

NTSB number

FTW01LA087

Nobody was injured.

the loss of tail rotor control during maneuvering resultant from the failure of the tail rotor drive shaft coupling due to a stripped thread which allowed the grease lubricating the shaft to leak out. A factor was the lack of suitable terrain for the forced landing (autorotation).

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

Read the full NTSB narrative

During a night flight, the helicopter was in level flight, about 1,400 feet MSL over a lake as the student pilot commenced a turn to the left with a forward airspeed of about 45 to 50 knots. The CFI then "came onto the controls" to assist with the coordinated turn, and noticed that the cockpit turn indicator showed that the helicopter was "slipping." Subsequently, the CFI applied left pedal to correct, and as soon as the left pedal was applied, the airframe shuddered and started to yaw to the right. The airspeed started to decrease and the helicopter began to "spin to the right rapidly." The CFI then applied full left pedal and the helicopter continued to spin to the right. After lowering the collective and reducing the throttle, the helicopter stopped spinning. The CFI then lowered the nose and maneuvered the helicopter toward shallow water near the heavily vegetated shoreline, flaring and pulling up on the collective to cushion the landing. The helicopter came to rest on its left side in the shallow water. Examination of the helicopter revealed that the splined coupling at the aft end of the forward tail rotor drive shaft segment was damaged. Removal of the dust cover for the coupling revealed that the screw and washer, part numbers AN501A10-4 and AN960-10, were loose with several of the threads stripped, thus allowing grease to weep during operation. The forward tail rotor drive shaft assembly, part number 47-644-18-9, was replaced on January 29, 2001. The helicopter had accumulated 70 hours of flight time since the last 100- hour inspection and 23 hours since the last 50- hour lubrication.

Quoted verbatim from the NTSB record.