Bell 206B N5743W

Summary

On 18 August 2015 at about 18:30 local time, a Bell 206B registered N5743W, operated by Fly Hangar 13 LLC, was involved in an accident near Cresco, Iowa, United States. One person was 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

18 August 2015 at 18:30

Classification

Accident

Location

Cresco, Iowa, United States

Coordinates

43.3653, -92.1331

Aircraft

Bell 206B

Registration

N5743W

Category

Helicopter

Year built

1980

Engines

1

Operator

Fly Hangar 13 LLC

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Cresco → Cresco

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN15LA370

Nobody was injured.

The loss of engine power due to the high-cycle fatigue failure of the third-stage turbine wheel.

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

Read the full NTSB narrative

The commercial pilot reported that the helicopter departed with 30 gallons of fuel and about 90 gallons of chemical to spray a soybean field. About 5 minutes into the application flight and while 3 to 5 ft above the soybeans, the pilot heard a loud screech for about 2 seconds and pulled up to gain altitude. The pilot then heard the low rotor rpm horn and noticed that the main rotor rpm was at 85 percent. The pilot initiated an autorotation to a waterway between two cornfields. Upon touchdown on uneven terrain, the main rotor blades contacted and severed the tailboom, and the helicopter then came to rest upright. Disassembly of the engine revealed that the third-stage turbine wheel was missing five airfoils (blades), that several other airfoils were damaged, and that portions of the shroud were liberated. Materials examination of the third-stage turbine wheel revealed that the five airfoils had cracked in fatigue, initiating from the trailing edge root area and progressing forward until final fracture occurred in overload. All five cracks had initiated and progressed in high-cycle fatigue. Extensive testing by the engine manufacturer could not identify a single root cause for the liberation of the airfoils. As a result of the investigation, the engine manufacturer planned to release a new wheel design and process improvements to improve the robustness and capability of the turbine wheel.

Quoted verbatim from the NTSB record.