A fatal mistake: how a single lever caused a catastrophic engine stall
In short: On 15 January 2023, Yeti Airlines Flight 691 crashed in Nepal, killing everyone on board. The cause wasn't mechanical failure, but a tragic human error: a pilot accidentally feathered the engines, cutting all thrust just seconds before the aircraft lost control and plummeted into a river.
The crash of the ATR 72-500, registered as 9N-ANC, occurred during a flight from Kathmandu to Pokhara. The investigation revealed that the aircraft was being used for an unplanned training session, as senior captain Kamal KC was instructing Captain Anju Khatiwada on the newly opened Pokhara International Airport. This increased the workload for the crew during a critical phase of flight.
The technical cause was a loss of thrust caused by the propellers being placed in a 'feathered' position. In an ATR 72, the condition levers—which control the propellers—are located next to the flap lever. Investigators found that Captain KC had inadvertently moved the condition levers instead of the flap lever. This meant that for about a minute before the crash, the engines were producing no thrust, leading to an aerodynamic stall.
The disaster resulted in 72 deaths, including 68 passengers and 4 crew members. It stands as Nepal's deadliest domestic aviation accident and the deadliest involving an ATR 72. Beyond the immediate error, the final report released on 28 December 2023 highlighted systemic issues, including a lack of approved approach circuit charts and failures in crew resource management and standard operating procedures.
A committee headed by Nagendra Ghimire and various global agencies found that the plane was sending incorrect altitude and speed information throughout its journey. The crash occurred on the banks of the Seti Gandaki River, just 65 metres from where a ground-filmed video captured the plane banking steeply before impact.
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- Summary by Intellect · source: Yeti Airlines Flight 691
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