Yeti Airlines ATR 72-500
Source: TMLN 123
What is the cause of an airplane stall during landing and how can it be prevented?
A stall in a plane is unlike a car – the engine does not stop. It is a condition when the airspeed becomes too low and the plane just drops off the sky unless corrective action is taken in time by the pilot.
The stalling speeds vary with each type of plane and comes about when its critical angle of attack or the angle between the body’s reference and the oncoming air-flow, around 15 to 18 degrees is exceeded.
This is the most important lesson a pilot learns on his first flight. He must also master the principle of flight on the Bernoulli theorem and the Newtonian theory on lift.
A stall arises when the smooth airflow over the wings breaks down. The lift would decrease and unable to support the plane’s weight. Consequently, it sinks and falls off the sky even with the engines still running.
If, for example, the stalling speed of a plane is 100 knots (115 mph) and a careless pilot allows the speed to decelerate below that, it would plunge into the ground.
The corrective actions include pushing the nose down to reduce the angle of attack, keeping the wings level and then adding power to resume normal flight.
This was not what the pilot of an US Colgan Air Flight 3407 did on a Bombardier Q400 flight from Newark, New Jersey to Buffalo, New York on February 12, 2009
Despite having stick shakers on the plane to warn the pilot of an impending stall, the pilot reacted wrongly and also overrode the stick pusher that would have prevented the crash.
It was reported that crew fatigue and icings were the contributory causes of the accident but the final findings stated that “airspeed mismanagement” led to the crash.
The most recent tragedy was on a Nepalese Yeti Airlines flight from Kathmandu to the tourist town of Pokhara on 15 January, 2023
After watching a video of the crash, Amit Singh, an experienced pilot and founder of India’s Safety Matters Foundation reported that the aircraft’s nose was noticeably high before the left wing suddenly dropped, indicated a likely stall.
Professor Ron Bartsch, an aviation safety expert and founder of Australia’s Avlaw Aviation Consulting, told Sydney’s Channel 9 that he also thought the plane appeared to have gone into a stall.
However, the Yeti Airlines spokesman said the cause of the crash was still under investigation.
The pilot flying this ATR 72-500 was a lady pilot who was being checked out as a captain by another examiner acting as a co-pilot.
Tragically, she had also lost her husband in a plane crash 16 years ago on the same airline. She had reportedly used the insurance money to train as a pilot in the US.
As to how such a dangerous condition can be prevented, airlines must ensure that their pilots practice the stall recovery procedures on a regular basis in the flight simulators to guarantee that such accidents would never happen again.
View a YouTube video ‘Aviation expert reveals likely cause of Nepal plane crash’