Eurocopter AS-350B-3 N405AE

Summary

On 23 September 2000 at about 21:45 local time, a Eurocopter AS-350B-3 registered N405AE was involved in an accident near Ketchikan, Alaska, 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

23 September 2000 at 21:45

Classification

Accident

Location

Ketchikan, Alaska, United States

Coordinates

55.6096, -131.5800

Aircraft

Eurocopter AS-350B-3

Registration

N405AE

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC00LA132

Nobody was injured.

The pilot's inadvertent activation of the collective flight stop/emergency fuel augmentation switch, which resulted in engine and main rotor overspeeds, thereby precipitating failures of the tail rotor drive shaft coupling and power turbine blades. A factor associated with the accident was the manufacturer's inadequate design of the flight stop switch, which has insufficient safeguards to preclude inadvertent activation.

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

Read the full NTSB narrative

Two commercial helicopter pilots, both certificated helicopter instructors, were in a turbine-powered helicopter practicing autorotations with a power recovery prior to touchdown. The flying pilot inadvertently activated the flight stop augmented fuel flow switch during a power recovery, and oversped the engine and main rotor. The other pilot joined him on the controls, and increased collective to reduce rotor rpm. The helicopter climbed abruptly to about 60 feet above the ground, where the tail rotor drive shaft separated. The engine subsequently lost power, and an autorotation was accomplished. Investigation disclosed that the engine and main rotor system had been exposed to significant overspeed conditions, resulting in a catastrophic failure of the turbine engine, and the tail rotor drive shaft coupling. The flight stop switch on the collective has no protective guard, and can be readily engaged, allowing the engine to enter the augmented fuel flow regime and, under certain conditions, causing the engine to overspeed. The switch has a history of inadvertent activation, and resultant engine overspeed events.

Quoted verbatim from the NTSB record.