Bell 47D1 N16356

Summary

On 10 November 2005 at about 21:00 local time, a Bell 47D1 registered N16356 was involved in an accident near Rancho Murieta, California, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

10 November 2005 at 21:00

Classification

Accident

Location

Rancho Murieta, California, United States

Coordinates

38.4044, -121.0883

Aircraft

Bell 47D1

Registration

N16356

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Rancho Murieta → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX06LA030

1 person was seriously injured.

a separation of the tail rotor assembly due to the reverse bending fatigue fracture of a tail rotor pitch change link bolt, resulting in a loss of control of the helicopter, and a hard landing during the uncontrolled descent.

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

Read the full NTSB narrative

The helicopter landed hard following the in-flight separation of the tail rotor assembly. During cruise, the pilot felt a vibration in the anti-torque pedals and attempted to make a precautionary landing in an open field. The tail rotor assembly separated prior to the pilot reaching the landing spot and the helicopter started to rotate and landed hard. The helicopter bounced back into the air, struck the ground again with the transmission bending over the cockpit area. Examination of the tail rotor assembly revealed that one of the pitch change links bolts had separated with the shank portion broken from the threaded portion of the bolt. A metallurgical examination of the bolt revealed that the fracture surface of the shank portion had been subjected to reverse bending fatigue. The arced lines were symmetrical on each side of the shank that culminated in a thin, dark, hourglass-shaped region in the center of the two arced lines. Burnishing observed on the fracture was typical of failures in bolts that have not been properly preloaded.

Quoted verbatim from the NTSB record.