Investigators have determined that a pilot operating a US-Bangla Bombardier Q400 was under stress, before the aircraft crashed on 12 March last year at Kathmandu Tribhuvan international airport.
In its final report, the Nepal Accident Investigation Commission found that the pilot was "emotionally disturbed" after a personal conversation in the cockpit with a colleague went sour.
"The effect of stress was evident with the fact that he was irritable, tensed, moody, and aggressive at various times. He also seemed to be fatigued and tired due to lack of sleep the previous night as well as due to the stress he was harbouring," adds the report.
The flight crew's failure to follow the standard operating procedures at the critical stages of the flight contributed to a loss of situational awareness.
In turn, this led to the aircraft's deviating from its flightpath which did not allow the flight crew to sight the runway, resulting in the crew's flying the aircraft "at very low altitude" with warnings present.
When the flight crew finally sighted the runway, they were very low, too close, and not properly aligned.
The pilot-in-command manoeuvred the aircraft in "a very unsafe manner by forcing it to land while in a turn", causing the right-hand main landing gear to impact hard, left of the centerline, approximately 1,700m from the threshold.
After touchdown the Q400 veered off the runway, hit a perimeter fence and rolled down a slope into a grass field before catching fire, resulting in 51 fatalities including all four crew. Twenty passengers survived with serious injuries.
The Q400, registered S2-AGU, was written off. Flight Fleets Analyzer shows that it was owned and managed by US-Bangla.
As part of its recommendations, the Nepal Accident Investigation Commission has informed the Civil Aviation Authority of Bangladesh that all airline pilots should undergo psychological evaluation as part of the training or before entering into the service.
The psychological segment of initial and recurrent aeromedical assessments, it adds, should be strengthened.
US-Bangla has been informed that it should establish an effective mechanism to monitor and assess mental status of the crew in regards to profession development, financial issues as well as personal and psychological issues.