Crews recovered the flight data recorder and cockpit voice recorder from the crash site Monday.
Yeti Airlines Flight 691 crashed on Sunday just before landing in the Nepalese resort town of Pokhara, the gateway to a popular Himalayan trekking area, after a 27-minute journey from Kathmandu.
At least 69 of the 72 people on board have been confirmed dead.
The pilots say Nepal can be a difficult place to fly, but the weather was fine at the time of the crash, with little wind, clear skies and temperatures well above freezing. So what could have caused the ATR 72 twin-prop plane to crash?
Did the plane stall?
Dramatic cellphone video taken from the ground shows the final seconds before the plane plunged about 1.6 kilometers (a mile) from the newly opened Pokhara International Airport. The aircraft’s nose rises noticeably before the left wing suddenly drops and the plane disappears from view on the video, indicating a probable stall, explained Amit Singh, an experienced pilot and founder of Safety Matters, an Indian foundation. safety matters).
“If you look at the trajectory of the aircraft, the nose to the plane goes up, and the nose up would be associated with a reduction in speed,” he told The Associated Press. “When they have a draft, usually one wing goes down and the wings basically create lift. So as the airflow is reduced, the lift generated is not enough to hold the aircraft in flight and the wings droop and the aircraft plummets.”
Professor Ron Bartsch, an aviation safety expert and founder of Australia’s Avlaw Aviation Consulting, told Sydney’s Channel 9 he also believes the plane has stalled. Its proximity to the ground possibly led pilots to believe its speed was higher than it actually was, he added.
“I would point out that the plane stalled,” he said after reviewing the video recorded just before the accident. “Possibly pilot error.”
Yeti Airlines spokesman Pemba Sherpa said the cause of the crash was being investigated.
Questions about the aircraft
The ATR-72 was introduced in the late 1980s, manufactured by a French and Italian joint venture, and although it has been involved in several fatal accidents over the years—some due to icing problems—in General has a “very good track record,” Bartsch said.
Crews recovered the flight data recorder and cockpit voice recorder from the crash site Monday, but it won’t be until they are carefully analyzed that investigators will know for sure what happened.
“Human factors will be one element that researchers will look at to see if there was adequate training or not,” Bartsch added. “But normally planes don’t fall out of the sky, particularly modern planes.”
Some kind of technical glitch with the aircraft’s instruments may have given pilots incorrect data, but even then it’s possible to recover from a stall problem, Singh said.
“Pilots must be trained to handle technical failures,” he added.
Singh stressed that Nepal’s aviation sector has a poor record on safety and training despite its “challenging airports and conditions.” Although it has been improving, its planes are prohibited from flying into European airspace, he stressed.
A pilot who regularly flies an ATR-72-500 plane from India to Nepal said the region’s topography, with its mountainous peaks and narrow valleys, increases the risk of accidents and sometimes requires pilots to fly depending on your own eyesight instead of the instruments.
The pilot, who works for a private Indian airline and who asked not to be named due to company policy, called the ATR-72-500 an “unforgiving aircraft,” even if the pilot is not highly trained and unfamiliar with the terrain and wind speed of the region.
ATR said on Twitter on Sunday that its specialists were “fully committed to supporting both the investigation and the clients” and that its “first thoughts are with everyone affected by this.”
The company did not immediately respond to requests for further comment.
Concerns about the new airport
Home to eight of the 14 highest mountains in the world, Nepal has a history of plane crashes. According to data from the Safety Matters Foundation, there have been 42 fatal plane crashes in Nepal since 1946.
The country’s “hostile topography” and “various weather patterns” were the biggest challenges, according to a 2019 safety report by the Nepal Civil Aviation Authority, which also resulted in a “series of accidents” involving small aircraft. According to the report, these accidents occurred at airports with short runways for takeoff and landing, and most were due to pilot error.
Pokhara Airport, a popular tourist destination that serves as the gateway to the Annapurna mountain range, sits at an elevation of about 820 meters (2,700 feet).
Before the airport opened two weeks ago, some expressed fear that the significant number of birds in the area — due to the habitat provided by two rivers and a landfill near the airport — could make it even more dangerous.
During the official inauguration of the airfield, the city’s mayor said that works to mitigate the effect of the dump had been completed, according to local press reports, but it was not clear what specific measures were taken.
If the aircraft had been struck by a bird as it was about to land, this may have led the pilots to break their approach and turn around again, which could also have caused the engine to stall, Singh said.
“A strong thrust setting can cause a stall,” he explained. “Crew tend to mishandle stall maneuvers…so again the question is how the pilot dealt with the problem.”
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