Air Tractor AT 400 N7300M

Summary

On 21 August 2018 at about 13:50 local time, a Air Tractor AT 400 registered N7300M, operated by Ross Seed Co Dba, was involved in an accident near Grand Forks, North Dakota, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 August 2018 at 13:50

Classification

Accident

Location

Grand Forks, North Dakota, United States

Nearest airport

J J And T (MN81)

Coordinates

47.9939, -97.0722

Aircraft

Air Tractor AT 400

Registration

N7300M

Category

Airplane

Year built

1984

Engines

1

Operator

Ross Seed Co Dba

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

East Grand Forks → East Grand Forks

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR18LA234

1 person was seriously injured.

The loss of engine power while maneuvering due to the failure of the power turbine blade assembly for reasons that could not be determined based on available evidence.  

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

Read the full NTSB narrative

The pilot was maneuvering the airplane during an aerial application over a field. A witness noticed that the airplane’s final turn was different than previous turns. Just before the airplane impacted the ground, the witness noticed a puff of smoke or liquid coming from the airplane. As the witness was a distance away, she was not certain. During the impact, the airplane sustained substantial damage. Examination of the engine revealed circumferential rubbing marks due to contact between the compressor turbine disk assembly and power turbine (PT) disk assembly. Of the 41 PT blades, 18 were recovered, and those blades exhibited fracture surfaces consistent with overstress fracture under elevated temperatures. Impact marks were identified inside the exhaust duct. The fracture of these blades likely occurred at ground impact when the engine was operational. It is likely that one or more of the unrecovered PT blades failed for an undetermined reason during the flight and impacted adjacent PT blades and components, including the exhaust duct. The internal engine damage from the released blades caused the PT disc assembly to fail, resulting in a loss of engine power.

Quoted verbatim from the NTSB record.