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Helicopter Suffers Total Rotor Drive Loss After Takeoff (N846BP)

Yuma, AZ, US

On November 25, 2003, an Eurocopter France AS 350 B3 (registration N846BP) was involved in an aviation accident near Yuma, AZ. No fatalities were reported. Investigators recorded the probable cause as: The malfunction of the rotor drive system due to improper maintenance, which resulted in the uncoupling of the drive shaft during takeoff-initial climb. A factor associated with the accident is the undertorqued drive system bolts. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

A helicopter experienced a total loss of rotor drive seconds after takeoff at about 20 feet, resulting in a hard landing and substantial damage. Investigation found sheared bolts and missing cotter pins on the flex coupling.

Accident Overview

A helicopter encountered a total loss of drive to the rotor system a few seconds after takeoff, when the aircraft was approximately 20 feet above the ground. The helicopter subsequently touched down hard and sustained substantial damage.

Maintenance History

Company mechanics had performed maintenance on the helicopter that involved handling of the rotor drive shaft and a flex coupling. The flex coupling is normally secured with three bolts and self-locking nuts. The manufacturer's maintenance procedure requires that during installation, the nuts are torqued and then cotter pins are inserted.

Wreckage Examination

During the examination of the wreckage, the bolts were found sheared. No evidence of cotter pins was found in the wreckage.

Manufacturer's Statement

According to the manufacturer, even if the cotter pins are not installed, if the bolts are adequately torqued, they should not become loose.

Maintenance error

Frequently asked questions

What happened in the 25 Nov 2003 Eurocopter France AS 350 B3 accident near Yuma, AZ?

A helicopter experienced a total loss of rotor drive seconds after takeoff at about 20 feet, resulting in a hard landing and substantial damage. Investigation found sheared bolts and missing cotter pins on the flex coupling.

Were there any fatalities in the 25 Nov 2003 Eurocopter France AS 350 B3 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 25 Nov 2003 involved an Eurocopter France AS 350 B3, registration N846BP, at Yuma, AZ.

What was the probable cause of the accident?

The malfunction of the rotor drive system due to improper maintenance, which resulted in the uncoupling of the drive shaft during takeoff-initial climb. A factor associated with the accident is the undertorqued drive system bolts.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20031219X02069. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.