Bell 206L-3 N27AE

Summary

On 24 May 1998 at about 17:35 local time, a Bell 206L-3 registered N27AE, operated by Air Evac EMS, Inc., was involved in an accident near Springdale, Arkansas, United States. 3 people were on board and 3 were seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

24 May 1998 at 17:35

Classification

Accident

Location

Springdale, Arkansas, United States

Coordinates

36.1799, -94.1402

Aircraft

Bell 206L-3

Registration

N27AE

Category

Helicopter

Engines

1

Operator

Air Evac EMS, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Unknown → Bella Vista

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

FTW98FA239

3 people were seriously injured.

The failure of maintenance personnel to properly assemble the engine's accessory gearbox, which resulted in a total loss of engine power due to partial blockage of the main oil passage by an o-ring. The blockage reduced oil flow to the turbine shafting, which led to the total failure of the gas producer turbine shaft and the power (free) turbine shaft. A factor was the lack of suitable terrain for the forced landing.

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

Read the full NTSB narrative

Shortly after the helicopter lifted off from a hospital helipad en route to pick up a patient, the engine lost power. The helicopter descended into a parking lot, landed hard, and rolled over coming to rest on its right side. Disassembly of the engine revealed that both the N1 (gas producer turbine) and the N2 (power turbine) shafts had separated. Coke deposits and rub marks were noted on the outside diameter of the N1 shaft. Coke deposits were also present on the inside diameter of the N2 shaft. Metallurgical examination of the shafts determined that coke build up consistent with reduced oil flow led to rubbing between the shafts. The rubbing produced frictional heat that resulted in softening and subsequent failure of the shafts. An o-ring was found lodged in the main oil passage of the accessory gearbox housing. Oil flow testing and calculations showed that this o-ring reduced the oil flow to the turbine shafting from .82 to between .00 and .10 lbs/min. Maintenance records indicated that the engine had accumulated 531 hours since a 3,500 hour gear train inspection, which included disassembly, cleaning, and reassembly of all accessory gearbox components.

Quoted verbatim from the NTSB record.