Old 25th May 2019, 16:18
  #25 (permalink)  
Two's in
Below the Glidepath - not correcting
Join Date: Jun 2005
Location: U.S.A.
Posts: 1,730
Originally Posted by lennystyles View Post
I'm an airline pilot and came across this accident and was just curious what the pilot could have done, once he put himself into this position?
Bearing in mind I just know the aerodynamics of a plane;
Could he have powered himself out of this position or was the plane essentially stalling?

Thanks in advance.
The problem was when he lost forward airspeed, the torque reaction from the main rotor began to overcome the anti-torque moment provided by the tail rotor. This caused the aircraft to yaw to the right despite full left pedal. The combination of a tail wind component, high power and zero airspeed overcame the tail rotor authority. The application of more power simply made the situation worse and increased the torque driven yaw, so no, he couldn't (and didn't!) "power" his way out of it. He had a number of options, all of them poor. He could have lowered the nose and attempted to regain positive airspeed, this would have provided aerodynamic forces to counter the yaw, but in this case he would have been descending and accelerating towards the river bank and structures, so this may not have been appealing. He could have reduced the power until the anti-torque force countered the yaw, but again, this meant descending towards the river and the bank waiting for the rotation to stop, not an obvious choice. Or, if he could have maintained a more stable platform, the rotational speed might have decayed as the aircraft came back into the wind, allowing him to transition away into the wind and regain positive airspeed quicker, but again, it's a brave man who can hold it in a level flat spin waiting for the rotation to slow down.

As you see from the video, all this happened very quickly, and this guy was only thinking of repositioning to a spot following a refuel. He probably wasn't considering the finer points of countering an unstable rotational acceleration with a limited anti-torque force following the loss of translational lift in a down wind configuration. But he will next time.
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