What caused the US-Bangla plane crash?

The Kathmandu Post pieces together details about the moments leading to the Bangladesh airline disaster. Here’s what it says:

Did faulty communication or technical malfunction cause the crash of Flight Bangla Star 211 at Kathmandu’s Tribhuvan International Airport (TIA)? On Monday, 49 people died when a US-Bangla Airlines plane carrying 71 passengers and crew crashed on “abnormal” landing at TIA.

The exact cause of the crash remains unclear. The authorities have started an investigation. The initial reports—video and audio recordings—indicate the 78-seater US-Bangla Airlines Bombardier Dash 8 Q400 aircraft had sustained a technical issue.

Passengers who survived the crash said sustained shuddering few minutes before the crash followed a loud bang. Ashish Ranjit, a travel agency operator in Balaju, recuperating at Norvic International Hospital, Thapathali, said, “Before the incident, I could sense the danger, the plane was wobbling horribly. I was scared and called an air-hostess. She raised her thumb indicating everything is ok,” he said.

What caused the plane to wobble?

“It’s normal during this time of year (February-April) that strong winds and turbulence try to blow the plane,” said Tri Ratna Manandhar, former director general of the Civil Aviation Authority of Nepal, who has vast experience as an air traffic controller. In March, an international aircraft tried twice to land at the TIA, but failed due to the crosswind.

The case of Flight 211 seems different as per the audio conversation. “The weather, especially the wind is normal. The captain is cool and calm while communicating with the ATCs.”

“It’s a mystery why the aircraft made a sharp right turn from north-west to east over the ATC tower,” he said. “It’s abnormal.” Obviously, it is difficult to land at the TIA given its vast terrain, but pilots who fly in Kathmandu are “specially trained”.

They have to do separate simulator training for Kathmandu’s airport landing. The US-Bangla Airlines Captain Abid Sultan, a former pilot of the Bangladesh Air Force, had landed more than 100 times at Kathmandu. Sultan had more than 5,000 hours of flying experience.

“Based on his experience, we cannot immediately judge that the captain was disoriented,” said a Nepali pilot, who flies in the domestic route. Captain Pawandeep Singh, a pilot with Indian airlines, told the BBC that the recording showed that there was confusion in the cockpit. “I am not sure what specifically happened in this case, but it seems like there was miscommunication while the pilot was trying to land the plane. We will know the complete truth only when investigators file their report,” the BBC reported, quoting the Indian pilot.

Manandhar argues the ATC had cleared the runway on both sides for Flight 211 to land when the aircraft was at the north side of the runway.  The radio conversation tells the flight was permitted to land from the runway 02 (Koteshwor side), but it abruptly broke the path and proceeded towards north-a surprise for the ATC.

So did the aircraft sustain a technical issue? The issue cannot be ruled out given the abnormal behaviour of the Flight 211.

On Tuesday, a local news portal shikharnews.com posted a video of the flight US-Bangla Airlines that shows that the aircraft was flying very low at Gagalphedi, northeast of Kathmandu. The video shows it nearly crashed at a foothill of a hill. The aircraft, however, managed to lift with white light visible from the wing tip that illuminate the terrain. Locals are heard chatting: The aircraft has lost its way. It is flying. It is flying.

At this point, in the audio conversation, Nepali pilots on the ground are heard warning the ATC that the Flight 211 pilot seems disoriented and that he should be assisted by radar vectoring, as the visibility in the hills is bad.

Experts said that aircraft never crash because of one single issue. It is almost always a combination of factors. The mechanical breakdown on its own should not have meant the plane crashed, but could have been handled correctly by the pilots.

Therefore, statistics for the causes of aircraft crashes are not always clear.

The following statistics are a reasonable representation: 55 percent pilot error, 17 percent aircraft mechanical error, 13 percent weather, 8 percent sabotage (lightning strikes) and 7 percent other like ATC and ground handling.