Hughes 369 N420AT

Summary

On 17 September 2021 at about 14:30 local time, a Hughes 369 registered N420AT, operated by DAT Aircraft LLC, was involved in an accident near Ash, North Carolina, 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

17 September 2021 at 14:30

Classification

Accident

Location

Ash, North Carolina, United States

Coordinates

34.0614, -78.5200

Aircraft

Hughes 369

Registration

N420AT

Category

Helicopter

Year built

1974

Engines

1

Operator

DAT Aircraft LLC

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA21LA368

Nobody was injured.

A partial loss of engine power due to corrosion and erosion damage to the engine’s compressor section components.

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

Read the full NTSB narrative

The pilot flew the helicopter from his home base to a remote aerial application site, where he landed the helicopter on a support truck so that the ground crew could load the chemical hopper. After loading was completed, the pilot increased the throttle until the engine and rotor rpm needles were in the green range of the tachometer. Immediately after liftoff from the truck, the pilot heard the low-rotor rpm warning horn, and the helicopter began to descend. The pilot attempted to add more pitch; however, the helicopter did not respond. The helicopter subsequently descended, impacted a field, and rolled over onto its right side, resulting in substantial damage to the tailboom. Postaccident examination of the engine revealed that it would start and run but could not reach full operating speed. Upon disassembly of the compressor section, significant erosion and corrosion damage was found on the compressor case halves and stator vanes, which also exhibited structural damage that ranged from being fully rolled over to being severely distorted or twisted. Other stator vanes were missing. The polymer coating on the inside of the compressor case was eroded in several places. Many of the rotating blades of the compressor were mechanically damaged. Since 1986, the engine manufacturer has published guidance instructing operators to perform a daily water rinse of engine components if the engine was operating in a corrosive environment, to reduce the possibility of component damage from corrosion and erosion. The aerial application of agricultural chemicals creates such a corrosive environment. The damage to the blades and polymer coating were consistent with a buildup of chemicals that the daily wash would likely have mitigated. The significant erosion and corrosion damage on the blades and the polymer coating likely began at some point before the accident and resulted in a partial loss of engine power during the accident flight.

Quoted verbatim from the NTSB record.