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Watching this video, my attention was triggered by the quite firm right rudder deflection, just before the right wing stalls.

There's no information about what happened in the video description, yet searching for the immatriculation (19-8530) tells it occured on 4/5 july 2015 at Hunter Valley Airshow, Maitland airport, Australia, plane is a Just Aircraft SuperSTOL.

I could not find any report on the Australian Transport Safety Bureau, ATSB regarding this event.

Is there any report or does anyone know what happened there?

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  • $\begingroup$ Well you can hear the wind gusting in that microphone! Wind gusts are random and very fast changes in airspeed. Airspeed is what airplanes need to fly. $\endgroup$ Dec 29, 2021 at 4:46

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It appears to be a stall in the landing configuration. At a guess that was a STOL competition or a flight demonstration. Pilot appeared to be either making an approach to land, or a low altitude, low speed pass over the runway. There appears to be a stiff wind over the airfield at a time this happened. Looks like the pilot got careless and entered a stall by accident getting too slow and exceeding the critical angle of attack on the wings, thence must have been uncoordinated entering the stall as he enters the incipient phase of a spin just prior to impact. Just before the crash, the airplane appears to mush at an extreme angle. I’m guessing at this point is when the airplane finally stalled. This also could be a result of a gust factor which the pilot encountered. The pilot does appear to recognize that he is in a stall, and applies the appropriate correction to the situation ie full power, lower the nose, opposite rudder to prevent the spin entry, etc. But, by the time it happened and he realized what was going on, he was really too low at that point to do an effective stall recovery.

Probably the chief culprit here is the pilot just got too slow for the approach, Trying to fly the thing right on the ragged edge of a stall down to touchdown, in order to minimize the length of the ground roll for a competition. Then things went wrong or he encountered a gust of wind shear that resulted in the stall. Fortunately, he was going low enough and slow enough, that when he impacted terrain, he was not (or appears not) injured in the crash.

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    $\begingroup$ It's probably not a formal competition, otherwise, there would be a target and measurement lines. But maybe training, an air show, or just showing off. $\endgroup$ Dec 27, 2021 at 22:27
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    $\begingroup$ Yes if you watch it carefully, you can see the sink rate and descent angle go up which appears to raise the AOA well above 20 deg. The slatted wing won't brake cleanly but just kind of slowly drops out on you as you exceed its Clmax. An unslatted airplane with a 16 deg stall AOA instead of 24 degrees, would've broke harder sooner, and entered an autorotation and hit nose first, so the slats still saved him from a worse fate. That was an impressively gentle crash. $\endgroup$
    – John K
    Dec 27, 2021 at 22:51
  • $\begingroup$ @CarloFelicione so the right rudder input at 00:29 was for lateral gust compensation? $\endgroup$
    – user21228
    Dec 28, 2021 at 1:40
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    $\begingroup$ @qqjkztd Or just part of normal corrections to keep the flight path straight. Flying that slow requires large control inputs because the effectiveness of control surfaces is proportional with airspeed. $\endgroup$
    – slebetman
    Dec 28, 2021 at 3:57
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    $\begingroup$ The right rudder input was a jab to compensate for a large power increase that was applied at about the same time. $\endgroup$
    – John K
    Dec 28, 2021 at 5:08
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My take on it:

The important thing to note is the plane has leading edge slats. This means the stalling AOA is about 10 degrees higher than normal, in the mid 20 degree range, and you can get into a regime of extremely high drag and declining lift without the kind of sudden stall break you would expect with an unslatted wing. So, a situation that would trigger a departure and spin on a normal airplane instead just results in a gradual and moderate wing drop since the wing is still producing some lift, just less than the other one. So instead of a departure and spin nose first into the ground, you get a wing-low mush and hard landing.

The rudder wagging is just large inputs to keep the nose going straight and is probably a reaction to the large power changes as the plane starts to sink. It does appear to start to descend at a steep angle as the airspeed decays so the AOA would have been more than high enough to make a normal airplane spin straight into the ground, whereas the slatted wing sinks without fully stalling.

On windy days you tend to get a shear zone at about 100 ft give or take as surface friction slows the air closer to the surface. I always anticipate 5-10 knots of reduced performance shear when descending through 50-150 feet in strong headwind conditions like that. This plane should be able to slow to the low 30s or even high 20s with power on in that configuration, at an AOA of maybe 20 degrees or more. If a shear gust knocked off 5 kts, it can be enough to trigger a high sink rate on a slatted wing without an actual break and departure.

So he was slowing for his super duper STOL approach, planning to fly the last 50 feet of descent at a high power, high AOA, high drag slow flight configuration where his sink rate is controlled with power, got caught by at gust or shear that maybe dropped his airspeed a bit too much, and found himself in a backside-of-the-power-curve box with no escape, but was saved by the benign low speed behaviour afforded by the slats, which provided a wing-low mush into the ground instead of a stall-spin nose first.

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