Thrust reverser stowage leads to runway excursion

No fatalities • Troy, United States of America • Landing (descent or approach)

An aircraft experienced an uncontrolled runway excursion and subsequent fire after a collision with wildlife caused the thrust reversers to stow unexpectedly.

What happened

Shortly after touchdown on a 5,010-foot runway, the aircraft type struck two deer. The impact occurred approximately 1,500 feet down the runway, roughly 4.2 seconds after landing at a ground speed of 124 knots. Following the collision, the aircraft continued along the runway with smoking tires before veering off the right side near the runway's end. The plane crossed a taxiway, entered a ditch, and caught fire. While the aircraft was expected to stop within 850 feet under maximum braking, heavy skid marks indicated the plane traveled significantly further, exiting the paved surface and traveling an additional 500 feet across grass and dirt.

Post-accident inspections revealed that all three landing gear components had collapsed. The main tires showed significant wear, with rubber worn through in several areas. Although the crew had deployed the thrust reversers during the landing roll, the levers and throttles were found in the stowed and idle positions, respectively, at the time of investigation.

Findings

Investigators determined that deer fur became lodged in the squat switch of the left main landing gear following the initial collision. This debris likely caused the squat switch to become inoperative. Because the deployment of thrust reversers requires a valid signal from this switch, the loss of the signal caused the thrust reversers to stow automatically. This malfunction likely triggered the electronic engine control (EEC) to transition to a forward thrust schedule, increasing engine power to near takeoff levels. This unexpected increase in power contributed to the loss of directional control and the subsequent runway excursion. There were no fatalities reported in the incident.

Probable cause

The unexpected stowage of thrust reversers, caused by a malfunctioning squat switch following a wildlife strike, led to an unintended increase in engine power.

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Frequently asked questions

What happened in the 2001-01-14 Learjet 60 accident near Troy, United States of America?

An aircraft experienced an uncontrolled runway excursion and subsequent fire after a collision with wildlife caused the thrust reversers to stow unexpectedly.

Were there any fatalities in the 2001-01-14 Learjet 60 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 2001-01-14 involved a Learjet 60, registration N1DC, operated by Ark-Air Flight, at Troy, United States of America.

What was the probable cause of the accident?

The unexpected stowage of thrust reversers, caused by a malfunctioning squat switch following a wildlife strike, led to an unintended increase in engine power.

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