The pilots switched levers by “turning off” the engines – Corriere.it
Human error could have occurred on January 15th Nepal Yeti Airlines ATR. One of the pilots, moreover more experienced, would eventually confuse the lever by touching the one that “turns off” both engines instead of the other, to the one that moves the flaps in the wings. The condition is still necessary as the investigation is ongoing.
But the Nepalese and Western investigators, as well as three different pilots with at least four thousand flight hours on that sample explain to courier The dynamics, the maneuvers performed and the sounds recorded by the two black boxes rule out the technical problem and point the finger at the pilots’ activities.
Many questions remain unanswered. Among pilots, there is also a hypothesis that civil aviation authorities can ask the manufacturer to adjust the controls to avoid repeating the same mistake. Yeti Airlines ATR 72-500 took off in mid-January at 10.32 (local time) from Kathmandu airport and headed to the new Pokhara airport, where the plane landed for tourists and then headed towards the highest peaks in the world. But a minute before landing, the plane crashed, killing 72 people: 68 passengers and 4 crew members.
In recent days, the Nepal Investigation Commission published the preliminary report on the incident. To write the fourteen pages, the Nepalese got help from the French Transportation Safety Agency (BEA), the Canadian Transportation Safety Board, the European Aviation Safety Agency (EASA), and Pratt & Whitney, the engine manufacturer. Audio data (from the “Cockpit Voice Recorder”) and flight parameters (“Flight Data Recorder”) were extracted from black boxes at laboratories in Singapore.
On January 15, a Yeti Airlines ATR 72 was scheduled for four routes between Kathmandu and Pokhara with the same pilots: Experienced Commander Kamal K. And that day I accompanied Kamal KC to find out more about the new Pokhara Airport, which is a short distance away – but with a different runway direction – from the old airport and opened only two weeks ago. The two pilots had already flown a round trip between Kathmandu and Pokhara that day and thus took off in the third part of the Nepalese capital.
The first problems
The initial report wrote that Anju Khatiwada was in control of that flight and was therefore seated on the left, while Kemal KC on the right was actually an “observer” as an instructor pilot. At 10.51 36 seconds, the plane began descending towards the airport. At 10.56 and 12 seconds, the wing flap is extended 15 degrees to facilitate approach to the runway. The black boxes also record the landing gear deployment and fifteen seconds later the Anju Khatiwada autopilot takes off. Immediately afterwards, Captain Kemal K. C Adjust the flaps to 30 degrees and repeat the signal. “But the ‘flight data recorder’ shows no movement of the chips,” the investigators wrote.
Instead, what the black boxes record is a sudden drop of less than 25% in the power of both ATR engines. The document talks about the “feather condition” of the engines. “This means that the propellers are up, that is, parallel to the direction of flight,” Al explains courier One of the pilots was consulted. “The engines actually no longer generate thrust or resistance.” This maneuver is usually performed «when the engine stops and it is necessary to create the least possible resistance with the propeller: instead of placing it perpendicular to the air, it is placed parallel».
First aid and pain for relatives of passengers on the plane that crashed Sunday morning near Pokhara airport in Nepal: the 72 people on board (EPA)
Both pilots agree that “Yete’s two ATR engines have gone into ‘idle’ mode, that is, at least to prevent overvoltage.” At 10.56 and 36 seconds, the cockpit voice recorder stores an initial onboard error signal in the audio file. The two captains start consulting flight manuals to see what’s going on. At 10.56 07 seconds Anju Khatiwada was told twice that the engines were not running, and 11 seconds later the orders passed to Kamal KC. Meanwhile, Khatiwada repeats that there is no power from the engines.
At 10.57 and 24 seconds, at an altitude of 95 metres, the control arms begin to vibrate because the nose of the aircraft has exceeded the maximum safety values. “At this point, the ATR starts to stall,” the experts explain. The situation becomes unrecoverable: the plane suddenly swerves to the left at 10.57 26 seconds – a scene captured by someone who was at that moment on the balcony of his house – and six seconds later the ATR crashes. The two black boxes stopped recording data at 10.57 and 33 and 10.57 and 35 seconds, respectively.
But how could the two engines be “turned off” in flight? A person helping the Nepali investigation team explains that the most likely hypothesis is the exchange of cranes. Instead of using the flap controls, the pilots may have touched the propeller controls: both levers next to each other. «In all likelihood – explain two pilots – the captain did not lower the flaps lever to bring the angle from 15 to 30 degrees, but touched those for adjusting the propellers which, if returned from the state of ‘auto’ to ‘Ftr’ end up drawing power from the engines » .
If the dynamics are to be confirmed by the final investigative report, what interests the experts is how it was possible not only to confuse the cranes, but also to ignore the various alarms that usually go off in this situation. At such a low altitude, – the pilots explain, – the plane no longer had a chance and could no longer even solve the problem.
“Infuriatingly humble social media ninja. Devoted travel junkie. Student. Avid internet lover.”