Thrust reverser deployment leads to fatal aircraft accident

2 fatalities • Sundance, United States of America • Landing (descent or approach)

A private cross-country flight ended in a fatal terrain impact after an asymmetric thrust reverser deployment caused the aircraft to roll and invert during approach.

What happened

During a personal cross-country flight, a two-pilot crew was performing an approach to a landing runway. Surveillance footage from the airport recorded the aircraft's final moments, showing that as the plane reached the approach end of the runway, it began an unplanned climb and rolled to the left. The aircraft subsequently became inverted before striking the ground. The accident resulted in two fatalities.

Findings

Investigation of the wreckage revealed that the left thrust reverser was unlatched and open, while the right thrust reverser remained closed and secured. This asymmetric deployment created a significant left roll and yaw. Several mechanical and electrical issues contributed to this failure:

  • The aircraft lacked a nose landing gear ground contact switch, a component designed to prevent the thrust reverser from being operated while in flight.
  • Electrical testing of the cockpit throttle quadrant showed that the left stow microswitch was not functioning according to design specifications.
  • Disassembly of the microswitches revealed arc wear caused by aging components.
  • Additional unairworthy components within the thrust reverser system were identified, though the extent of their impact could not be tested due to the wreckage damage.

Investigators also examined the pilot's toxicology report, which showed the presence of diazepam. However, because the levels of the drug and its metabolite were subtherapeutic and consistent with medication taken several days prior, the presence of the substance was not considered a contributing factor. The investigation was further complicated by the absence of a functional cockpit voice recorder, which prevented the identification of specific crew actions or flight deck communications.

Probable cause

The asymmetric deployment of the left thrust reverser, caused by aging microswitches and the absence of a ground contact switch, led to a loss of control during approach.

Frequently asked questions

What happened in the 2019-03-18 IAI 1124 Westwind accident near Sundance, United States of America?

A private cross-country flight ended in a fatal terrain impact after an asymmetric thrust reverser deployment caused the aircraft to roll and invert during approach.

Were there any fatalities in the 2019-03-18 IAI 1124 Westwind accident?

The accident was fatal, resulting in 2 fatalities.

What aircraft was involved and where did it happen?

The accident on 2019-03-18 involved a IAI 1124 Westwind, registration N4MH, operated by Sundance Airport FBO, at Sundance, United States of America.

What was the probable cause of the accident?

The asymmetric deployment of the left thrust reverser, caused by aging microswitches and the absence of a ground contact switch, led to a loss of control during approach.

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