Nepal plane crash

[zakthor]

Sorry I'm a layperson. I've read the comments above and still don't understand what happened.

That left wing drops so fast. Right wing had lift until plane was sideways?

Was this the pilot's doing? Drop the left wing a bit in order to turn, speed too low so left wing stalled (and not right wing?) Maybe cut the left throttle too much and that lost the lift?

Happened so quickly. Turned into a brick. Is that what planes do? I'd have thought pilot would react to keep plane flat and we'd see the elevators flapping madly.

Pokhara isn't high altitude, its less than 3000ft.

[Jeff Higgins]

"Density altitude" is the issue here. "Sea level", or zero altitude, is established at a nominal temperature and humidity at, not surprisingly, sea level. Raise the ambient temperature and raise the humidity, and even "sea level", right there on the water, can have "altitude" of hundreds, if not a couple thousand feet.

At 3,000 feet above sea level, in a hot and humid environment, the "density altitude" can be much, much higher than that. That's what an aircraft "sees". It "thinks" it's at, say, 20,000 feet, and behaves accordingly.

So, yeah, the "inside" wing lost lift and stalled. Lots of reasons why it would lose lift first. It's a bit obstructed by the disrupted airflow around the fuselage, and it's moving a bit slower.

[greglepore]

She must have been well below msm or something. Almost looked like a turn into a dead engine. ATR's sure kill a lot of folks, entry level crews I guess.

[Adrian Thompson]

Does the inside wing, port in this case, stall because it's going around a tighter radius (inside of turn) than the outside wing so the air flow is less. Or is it because of the attitude it's at when looked at from in front? If one wing has stalled, wouldn't that mean almost certainly the other wing is about to stall? Not questioning anything said so far, just trying to understand what happened.

[Cajundaddy]

Yes. When an aircraft is very close to stall speed, exasperated by being nose up, a left turn reduces airflow slightly over the left wing and increases airflow over the right wing inducing a L wing drop stall. Attempting to lift the wing by applying aileron makes the problem worse. It is entirely possible that they suffered a bird strike or other mechanical problem causing their approach to become unstabilized at a critical moment. They were too low to recover once the left wing dropped.

Monday morning armchair quarterback debrief- The cockpit alarms were probably screaming a stall warning. If they had gone to full power and pushed over the nose to stabilize the aircraft and go around this might have been avoided. It was the only trick left in the bag in their situation.

More in-depth detail on a wing drop stall can be found here:
https://www.aviation.govt.nz/licensing-and-certification/pilots/flight-training/flight-instructor-guide/wing-drop-stalling/

[911 Rod]

Any chance she knew a crash was coming and put it in the ditch to avoid the homes?

[masraum]

Originally Posted by Cajundaddy

Yes. When an aircraft is very close to stall speed, exasperated by being nose up, a left turn reduces airflow slightly over the left wing and increases airflow over the right wing inducing a L wing drop stall. Attempting to lift the wing by applying aileron makes the problem worse. It is entirely possible that they suffered a bird strike or other mechanical problem causing their approach to become unstabilized at a critical moment. They were too low to recover once the left wing dropped.

Monday morning armchair quarterback debrief- The cockpit alarms were probably screaming a stall warning. If they had gone to full power and pushed over the nose to stabilize the aircraft and go around this might have been avoided. It was the only trick left in the bag in their situation.

More in-depth detail on a wing drop stall can be found here:
https://www.aviation.govt.nz/licensing-and-certification/pilots/flight-training/flight-instructor-guide/wing-drop-stalling/

My understanding is that what is most intuitive, is often the opposite of what needs to happen, as you explain. Trying to pull out of it, makes the situation worse. I think the solution is often counter-intuitive and to go in the direction that seems like it could make it worse. Obviously, there's a lot more to it than that.

[Cajundaddy]

Originally Posted by 911 Rod

Any chance she knew a crash was coming and put it in the ditch to avoid the homes?

The news reports were giving the flight crew the benefit of the doubt and we may never know. Once the left wing dropped at that altitude I fear all flight control was lost.

[zakthor]

Originally Posted by Cajundaddy

Yes. When an aircraft is very close to stall speed, exasperated by being nose up, a left turn reduces airflow slightly over the left wing and increases airflow over the right wing inducing a L wing drop stall. Attempting to lift the wing by applying aileron makes the problem worse. It is entirely possible that they suffered a bird strike or other mechanical problem causing their approach to become unstabilized at a critical moment. They were too low to recover once the left wing dropped.

Monday morning armchair quarterback debrief- The cockpit alarms were probably screaming a stall warning. If they had gone to full power and pushed over the nose to stabilize the aircraft and go around this might have been avoided. It was the only trick left in the bag in their situation.

More in-depth detail on a wing drop stall can be found here:
https://www.aviation.govt.nz/licensing-and-certification/pilots/flight-training/flight-instructor-guide/wing-drop-stalling/

Thanks for the explanation and the link. Is impressive it is a well documented thing.

I looked up the plane, it is much bigger than I thought it was and fooled my eye. I thought it was a little mountain plane but its huge and needs 1000 meters to land.

I've landed at pokhara and also at lukla before it was paved. The plane into Lukla was a turbine pilatus which has big deep wings for its size. Could feel its excess of lift even when landing at 9k feet.

This is a super sad thing.