US-Bangla Airlines Flight 211

US-Bangla Airlines Flight 211 was a scheduled international passenger flight from Hazrat Shahjalal International Airport in Dhaka, Bangladesh, to Tribhuvan International Airport in Kathmandu, Nepal, that crashed on 12 March 2018 while landing, killing 51 of the 71 people aboard. The aircraft, a 76-seat Bombardier Q400 operated by US-Bangla Airlines, burst into flames after the crash. The 20 surviving passengers were badly injured from the impact and the fire. It remains the deadliest aviation disaster involving a Bangladeshi airline, and the deadliest incident involving a Bombardier Dash 8 Q400.

A commission appointed by the government of Nepal investigated the accident and concluded that the probable cause of the crash was pilot disorientation and a loss of situational awareness of the flight crew. The report was criticized by the airline and by the Bangladeshi representative on the commission, who felt that the air traffic controllers at Tribhuvan International Airport did not do their job properly and could have prevented the accident.

Accident

The Bombardier Q400 turboprop aircraft operating as flight number BS-211, departed Hazrat Shahjalal International Airport in Dhaka, Bangladesh, at 06:51 UTC (12:51 pm Bangladesh Standard Time), bound for Tribhuvan International Airport in Kathmandu, Nepal. BS-211 was a regularly scheduled flight that operated four times a week between the two cities.

At 08:10 UTC, First Officer Prithula Rashid contacted Kathmandu Approach, who told the flight to descend to 13,500 ft and enter a holding pattern at a specified navigational waypoint. Long approach delays were common at Kathmandu, due to a lack of airport capacity and a high volume of traffic, so the instruction to enter a holding pattern was not unusual. Since they were slightly ahead of schedule, the pilots expected the delay to last several minutes, so they discussed the navigational elements of the holding pattern and configured the flight management system in preparation. However, before the aircraft had arrived at the holding point, the approach controller instead cleared the flight to descend and proceed directly to the approach for runway 02. The pilots had not reconfigured the flight management system for the approach, however, so when the aircraft arrived at the next waypoint, the autopilot began a left-hand turn of the aircraft as it had been configured for the holding pattern. Captain Abid Sultan realized that the plane was turning away from the intended course, and quickly changed the aircraft's autopilot heading selector to a course that would intercept the correct approach and manually adjusted the autopilot's rate of descent. These changes caused the aircraft's autopilot to switch to a mode where the course and rate of descent were controlled by the cockpit selectors instead of the aircraft's flight management system, which was programmed to automatically follow the course and the rate of descent to align with the targeted runway.

The crew performed the landing checklist, but Sultan erroneously stated that the landing gear was down and locked, when in fact, it was not. Because the flight management system was disengaged, the pilots had to manually adjust the aircraft's rate of descent, and failed to select a rate that kept the aircraft at its intended altitude throughout the planned descent. Rashid repeatedly called out that they were 500 to 600 ft too high compared to their desired altitude. Meanwhile, a gear-unsafe alert tone sounded continuously in the cockpit, unacknowledged by the pilots. With their attention focused on trying to adjust to the correct altitude, and distracted by the audible warnings, the crew failed to notice that the plane was still off course, and had by this time flown to the right of the desired approach path, descending at rates as high as 1,700 ft/min. Audible warnings of "MINIMUM", "SINK RATE", "TERRAIN", and "TOO LOW-GEAR" sounded, adding to the confusion. Rashid noticed that the landing gear was not down and lowered it, but by this time the aircraft had already passed the runway, and neither pilot was aware of it. The tower contacted the flight crew and informed them that they had been cleared to land on runway 02, but they appeared to be heading to runway 20, the opposite end of the single runway, and asked Sultan's intention. Still unaware that they had already passed the runway, he responded that he intended to land on runway 02. Seeing high terrain ahead of them, he performed a sharp right-hand turn, during which the aircraft descended to as low as 175 ft above the ground, and reached bank angles of up to 35 to 40°. This triggered additional alerts and alarms of "PULL UP", "TERRAIN", and "BANK ANGLE" in the cockpit. After flying to the west without spotting the runway, Captain Sultan calmly admitted to Rashid that he had made a mistake and had become distracted by talking to her, and performed another steep right turn, with bank angles as high as 45° and descent rates of over 2,000 ft/min.

Eventually, with air traffic controllers on the radio still trying to clarify where the aircraft was going and the plane flying in a southeasterly direction, Rashid spotted runway 20 at the aircraft's 3 o'clock position, about 2 nmi away, and Sultan made a sharp and abrupt right turn back to the west in an attempt to return to the approach end of the runway. The aircraft overflew the end of runway 20 on a heading of 255°, 450 ft above the ground, turning left with a forty-degree bank angle. Alarmed by the actions of the aircraft, the air traffic controller hastily cancelled the flight's landing clearance, erroneously calling out "takeoff clearance cancelled". The aircraft flew over the airport's domestic passenger terminal less than 50 ft over its roof, and controllers in the tower ducked down out of fear. The aircraft made another sharp turn in an attempt to line up with the runway before touching down at an angle 1700 m along the runway with its right main landing gear. The aircraft was travelling at the cockpit-indicated airspeed of 127 kn and a heading of 190 degrees when it hit the runway. The aircraft skidded off the runway, crashed through the inner perimeter fence on the edge of the airport, and slid down the slope. The aircraft disintegrated into pieces as it slid down the rough slope before crashing into the football field and bursting into flames. The aircraft came to a stop about 442 m southeast of the runway.