Air Tractor AT602 N604MG

Summary

On 20 August 2020 at about 14:00 local time, a Air Tractor AT602 registered N604MG, operated by Gary Flying Service, was involved in an accident near Inverness, Mississippi, 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

20 August 2020 at 14:00

Classification

Accident

Location

Inverness, Mississippi, United States

Nearest airport

Lester Field (MS21)

Coordinates

33.3369, -90.5814

Aircraft

Air Tractor AT602

Registration

N604MG

Category

Airplane

Year built

2019

Engines

1

Operator

Gary Flying Service

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Inverness → Inverness

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN20LA353

Nobody was injured.

The pilot’s decision to move the power control lever into beta during flight, which resulted in the power control lever and associated linkage becoming stuck in the beta position.

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

Read the full NTSB narrative

The turbine-powered agricultural airplane was on short final to land at the private airstrip. In attempt to slow down the airplane, the pilot actuated the power control lever (PCL) into beta, which caused the PCL, cam box, and associated linkage to get stuck in place. The airplane required more engine power to make the runway so he attempted to advance the PCL, but it would not move. The pilot made a forced landing in a field short of the runway, the airplane came to rest upright, and sustained substantial damage to both wings. The engine data revealed that the PCL was moved to beta while the airplane was on short final. The beta signal was still on after engine shutdown, which indicates that the cam box was likely stuck in beta. A service letter issued by the airplane manufacturer states that the use of beta mode in flight is not authorized and can result in a dangerous situation, leading to a loss of control. In this event, when the PCL was actuated into beta in flight and the propeller servo pressure dropped to maintain control of the propeller, the servo pressure went into a negative range, and the propeller blade angle was quickly forced to the max reverse stop, which allowed the beta ring to move to the most forward position. Since the beta valve does not allow this amount of movement, the additional movement of the beta ring was transferred to the cam box and the cam box jammed in place.

Quoted verbatim from the NTSB record.