Eurocopter AS350B2 N1231A

Summary

On 12 November 2010 at about 15:48 local time, a Eurocopter AS350B2 registered N1231A, operated by Tiny Bubbles, Inc., was involved in an accident near Pacoima, California, 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

12 November 2010 at 15:48

Classification

Accident

Location

Pacoima, California, United States

Nearest airport

Whiteman Field (WHP)

Coordinates

34.2594, -118.4136

Aircraft

Eurocopter AS350B2

Registration

N1231A

Category

Helicopter

Year built

2003

Engines

1

Operator

Tiny Bubbles, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Aerial Observation

Phase of flight

Not recorded

Route

Pacoima → Pacoima

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR11FA045

Nobody was injured.

The contamination of a spool bearing in the power turbine governor during manufacture, which led to the bearing’s failure in flight, a subsequent loss of engine power during departure, and the resultant hard landing.

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

Read the full NTSB narrative

During a downwind departure from the airport, the engine began to lose power. The pilot initiated an immediate autorotation back toward the airport while adjusting the airspeed and flight controls to clear power lines along the airport boundary. After clearing the power lines, the helicopter settled hard on the runway centerline and then began to rock, slide, and yaw right. The pilot attempted to regain control of the helicopter, and it eventually came to a stop upright on its skids facing about 160 degrees right of the runway centerline. The aft portion of the tail boom had separated. Postaccident testing and examination of the engine revealed a degraded power turbine (PT) governor spool bearing. Examinations also revealed the presence of diamond particles, which are used in the manufacturing process for the ball bearings, in the governor spool bearing. It is likely that diamond particle contamination caused the governor spool bearing to fail, which rendered the PT governor incapable of modulating governor servo pressure to the fuel control unit. Although no physical evidence was found indicating that the electronic overspeed system activated, the pilot's statement about two increases in rpm and then a decrease in rpm indicates that the system likely activated. The loss of PT governing ability coupled with the activation of the electronic overspeed system likely resulted in fuel flow oscillations that decreased the fuel flow below the lean blowout limit of the engine and led to the loss of engine power.

Quoted verbatim from the NTSB record.