The de Havilland DHC-6/300 had entered unexpected instrument meteorological conditions (IMC) during a visual flight rules (VFR) flight over mountainous terrain, and the pilot-in-command (PIC) was attempting to escape the weather when the Twin Otter struck a ridge. The aircraft was destroyed, and all 22 people aboard were killed. The report by the Aircraft Accident Investigation Commission of Nepal (AAIC) said that the Twin Otter was equipped with a terrain awareness and warning system (TAWS), which might have provided a two-minute warning about terrain ahead, but the PIC had disabled the system because it was providing false (“nuisance”) warnings. As a result, the flight crew received only one ground-proximity warning system (GPWS) alert before the aircraft struck the mountain.
