Here we go again

[Gabriel]

I am garbing my chair's armrests to constrain myself from re-starting not 1 rant but 2.

One is stalls.
The other one 3we will immediately know when he sees it.

https://www.youtube.com/watch?v=MFyd3Hc-WoQ

[elaw]

Yeah I just saw that one myself. Side note, that guy's videos just started popping up on my YT suggestions and so far I'm liking them.

As to the topic of vid, it's so strange that when you try to make airplanes climb faster than they can climb, they don't.

[elaw]

Another one from the same channel: https://www.youtube.com/watch?v=_PHuudwg868

Armrest-grabbing may still be required, to prevent falling from the chair due to excessive laughter.

[Gabriel]

Yeah I just saw that one myself. Side note, that guy's videos just started popping up on my YT suggestions and so far I'm liking them.

As to the topic of vid, it's so strange that when you try to make airplanes climb faster than they can climb, they don't.

I liked him too, until 5 minutes ago. And you should stop liking him too.
Anybody that promotes the misconception that is the source of my second (so far undisclosed) rant should not be liked by anyone in the aviation community.
ESPECIALLY if they "specialize" in doing training videos that analyze accidents and gives advice to be a safer pilot.

I still hope there is a misunderstanding, that is, that I misunderstood what he is saying.

[Gabriel]

From his "About" section in his channel:

My name is "Hoover". I served 20 years in the Air Force where I flew the F-15E "Strike Eagle". I also participated in an exchange program with the USMC where I flew the F/A-18D for three years. After retiring from the military, I spent a short time flying the CE-560XL for a Part 135 operator, and now I fly for a major US airline.

From someone with this background, this is inexcusable!!!!
Someone should hold his license until he receives remedial training.

PLEASE someone tell me that I am an idiot that I am not understanding a word of what he is saying!!!!
Come on Flyboy, you should have no problem doing that.

[Not_Karl]

misconception

Ban ALL downwind turns?

As to the topic of vid, it's so strange that when you try to make airplanes climb faster than they can climb, they don't.

They can, you only have to pull-up relentlessly.

[flyboy2548m]

PLEASE someone tell me that I am an idiot that I am not understanding a word of what he is saying!!!!
Come on Flyboy, you should have no problem doing that.

I'm sorry, what exactly is it that you're not understanding?

[Gabriel]

PLEASE someone tell me that I am an idiot that I am not understanding a word of what he is saying!!!!
Come on Flyboy, you should have no problem doing that.

I'm sorry, what exactly is it that you're not understanding?

Nothing. I did understand correctly, unfortunately.
The YouTuber confirmed in the comments that he is an F-15 / F-18 / Citation XL / Major Airline / dreaded downwind turn myth believer pilot.

I just don't get it. And to be honest it scares me a little bit knowing the the pilot the of airliner where I occupy 44D my have this level of misunderstanding about how the machine he very skillfully operates, operates.

[ocelot]

I am also not real impressed with the discussion of floatplane takeoff technique. Not that I'm an expert in it or anything, but he seems to have missed the point that if you pull_up and dig the floats in, you just aren't going to be getting off the water. Which is exactly what happened in the second crash.

The discussion of the first crash also leaves something to be desired. With insufficient roll authority to stay straight, you'd expect the plane to weathercock into the wind.

My feeling is that we should probably look for other speakists.

[Gabriel]

The discussion of the first crash also leaves something to be desired. With insufficient roll authority to stay straight, you'd expect the plane to weathercock into the wind.

What? Please explain what you meant.

[ocelot]

If you have a sideways AoA, because e.g. you're taking off into a crosswind, you'll be getting a yaw moment into the wind. The accident aircraft was turning downwind, and, supposedly, this was uncommanded/forced by the wind, and that seems like rubbish. Unless I guess we think a gust flipped the right wing up and then there wasn't enough roll authority to roll it back? But in that case the explanation offered is seriously lacking.

[3WE]

Repeat from there: There are three GENUINE risks to a downwind turn, and you address them the same as the Don Moore and many others Intuitive-but-wrong thought that you lose airspeed from the tailwind. So I won’t dig my fingers into the arm chair for a passing sentence regarding turning into a tailwind on a painful 10 minute video of guys crashing heavy floatplanes on windy days.

My main conclusion is that the dude (like many others) likes to hear himself talk.

As to the crash, I do not_disagree with Ocelot. He was heavy, drug the plane into the air…he levels the wings and IMO relaxes the climb… HOWEVER, my ass-umption is he was already slow and hit a wind gust/shear that dropped him below stall.

I also think that after years of pontificating against relentless pull ups, we have ignored subtleties of mushing and momentum: His attitude looked ok right before the stall…but was he already sinking? Also, if you push over your inertia shifts to a relative down, making it harder to relatively go up when you want to go.…but all taking place in what is NORMALLY a fat and happy attitude.

[Gabriel]

If you have a sideways AoA, because e.g. you're taking off into a crosswind, you'll be getting a yaw moment into the wind.

Yes, while you are rolloing on the grund or water. You need to use rudder to keep the plane from weathervaning.
Once in the air, if you are in coordinated flight, the wind comes always from straight ahead, no matter the wind speed or what turn you make.

The accident aircraft was turning downwind, and, supposedly, this was uncommanded/forced by the wind, and that seems like rubbish. Unless I guess we think a gust flipped the right wing up and then there wasn't enough roll authority to roll it back? But in that case the explanation offered is seriously lacking.

A GUST of wind can make you weathervane momentarily, but a gust can be in any direction: it can increase the wind speed, decrease it, or change its direction. So whether you turn upwind or downwind doesn't change that. It can happen if you turn upwind too.

[Not_Karl]

It can happen if you turn upwind too.

Ban ALL donwind AND upwind turns.

[ocelot]

If you have a sideways AoA, because e.g. you're taking off into a crosswind, you'll be getting a yaw moment into the wind.

Yes, while you are rolloing on the grund or water. You need to use rudder to keep the plane from weathervaning.
Once in the air, if you are in coordinated flight, the wind comes always from straight ahead, no matter the wind speed or what turn you make.

The accident aircraft was turning downwind, and, supposedly, this was uncommanded/forced by the wind, and that seems like rubbish. Unless I guess we think a gust flipped the right wing up and then there wasn't enough roll authority to roll it back? But in that case the explanation offered is seriously lacking.

A GUST of wind can make you weathervane momentarily, but a gust can be in any direction: it can increase the wind speed, decrease it, or change its direction. So whether you turn upwind or downwind doesn't change that. It can happen if you turn upwind too.

I think we're losing context. From what I recall (do not_have the patience to go watch the video again) the sequence of the first crash was that the plane appeared in the air suspiciously early and pointing to the left (downwind) of the takeoff direction, then veered further left in an increasing left bank, then dropped the left wing entirely (not necessarily that suddenly, IIRC) and splashed. And the question is what actually happened.

I'm not_arguing about turns to downwind, that's clearly not the point, even if it's what you were objecting to in the video.

ISTM that under normal circumstances if you take off with a right crosswind and don't have the technique down, you'll end up drifting left (downwind) but pointing to the right (upwind), for the reasons already cited. This isn't what happened. Therefore, something else must have been at work.

Now, it appears that the A/C doesn't have adequate roll authority at low speed. So one possibility is that it rolled left and the pilot couldn't roll back, and then in a misguided attempt to maintain coordinated flight instead of staying upright, applied left rudder, resulting in a left turn, increasing uncontrollable left bank, and possibly not even a stall, just a vertical bank and loss of lift. (Does the type in question have an autocoordination widget?)

Another possibility is excess left rudder, leading to a skid and then stall on the inside wing. Which seems insane, but maybe the rudder was mistrimmed or misrigged.

None of this made it into the video though, AFAICR.

(also note: like with a rough field takeoff, it's not inherently wrong to yoink the plane up as soon as it will fly, but you're similarly supposed to accelerate to a reasonable speed in ground effect, which clearly also didn't happen.)

[3WE]

Quote=Ocelot

1. I think we're losing context.

2….turns to downwind, that's clearly not the point…

3. So one possibility is…

1. I’m not sure we ever had context.

2. If you are Gabriel, that CLEARLY IS THE PRIMARY point. On the second (painful) listen, I heard the speakist briefly reference downwind turns and speed loss, and then return to relentless blabbering.

3. I’m comfortable with them being heavy and slow and in some decent gusty winds, that did this AND that and maybe Beavers aren’t 172s…

[Gabriel]

Now, it appears that the A/C doesn't have adequate roll authority at low speed. So one possibility is that it rolled left and the pilot couldn't roll back, and then in a misguided attempt to maintain coordinated flight instead of staying upright, applied left rudder, resulting in a left turn, increasing uncontrollable left bank, and possibly not even a stall, just a vertical bank and loss of lift.
Another possibility is excess left rudder, leading to a skid and then stall on the inside wing.

Of course I don't know what exactly transpired up there (well, not that up anyway), but here is a likely scenario based on past cases, fiziks, and a little bit of personal experience.

Roll handling characteristics suffers a lot at low airspeed and high angle of attack. The direct effect of low airspeed is that aerodynamic forces (including roll forces) go with the square of lift. But that's trivial. The indirect effect of low speed is that to fly low you need a high angle of attack, and a high angle of attack has several direct and indirect impacts in roll handling characteristics.

The first one is that the aileron becomes much more ineffective, if at all. If you look the lift vs AoA curve, you see that is a straight line at low angles of attack, there is a maximum point at an angle of attack called critical angle of attack, and after that the lift drops quite a bit quite quickly. But the curve doesn't remain a straight line all the way from low angles of attack to the critical angle of attack. At some hagfish angle of attack short of the critical one, it starts to slope down. That means that, in that range, every additional degree of angle of attack you add (keeping it still short of critical) adds less and less lift than in the "linear" range. The ailerons increase the effective angle of attack of that zone of the wing so when you are in that reduced-slope range, the change in aileron position has a smaller effect than at lower angles of attack.

The second effect, is the first effect taken to the extreme. Very close to the critical angle of attack the increase in lift by the aileron going down can be almost negligible, it may even cause that part of the wing to stall, causing that wing (the one you want to pick up) to actually drop, an effect called adverse roll. The FAA regulations require (well, required when the FAR 23 was an actual regulation and not just an interposer that just tells you to look at the ASTM standards) that the aileron have no adverse roll effect all the way to the stall, but not at the stall or beyond.

The third effect is that, the aileron going down always causes more drag than the aileron going up. In normal circumstances, far away from the stall and relatively small aileron deflections, that effect is caused because the aileron going down increases lift and with it the induced drag also increases. The parasitic drag also increases, but that's minor in normal circumstances. However at high angles of attack that effect is exacerbated because the induced drag is much higher, but on top of that the increase in parasitic drag also increases a lot on the down-going aileron because it will stick a lot in the wind, while the parasitic drag will reduce a lot on the up-going aileron because it "hides" in the shadow of the wing, and on top of that the aileron inputs at low speeds tends to be much larger to achieve the desired effect (especially when you feel you are about to fall out of the sky). The Tomahawk I used to fly, for example, didn't require any rudder to keep coordinated flight when applying small aileron inputs at cruise to perform a normal turn, but required much more (still not a lot) when trying to roll at the same rate at a slow speed like Vy (the speed of better climb angle). This effect is called "adverse yaw", because when you apply right roll aileron input (left aileron going down) the plane yaws left unless you compensate with rudder to keep it coordinated. Adverse yaw, if not avoided with rudder, will cause the wing you want to pick up to slow down and the one you want to lower to speed up, and will also cause a sideslip, with the corresponding decrease and increase of lift respectively (both for the difference in speed and for the dihedral effect), which will tend to roll the plane in the exact opposite direction.

There is a last effect, which I don't think it is relevan for this accident but is interesting. At the boundary of the stall and beyond, the airplane loses roll damping. Under normal circumstances, roll damping is achieved "automatically" because in the down-going wing when rolling the air hits more from below which increases the AoA and hence the lift, stopping the roll. So if you apply aileron to roll, or to level the wings, or the plane rolls itself due to an atmospheric disturbance, just centering the ailerons will cause the plane to quickly stop rolling and maintain its bank angle. That doesn't happen around the stall angle of attack because the lift of the down-going wing doesn't increase despite its angle of attack increasing. That makes the plane behave very different than normal. Under normal conditions, you apply ailerons to achieve a desired roll rate and center the ailerons when you want the roll to stop and the plane to keep the angle of attack. In the around-stall situation, and assuming that the ailerons are effective to roll in the desired direction (which may not be the case as discussed), you need to apply aileron to accelerate to a given roll rate, center ailerons to keep the roll rate, and apply opposite ailerons to stop the roll and center the ailerons again to keep the bank angle. It is doable but nobody will do it unless they have a lot of practice in that condition, which almost nobody does.

Because all of the above, you don't want to use aileron when you are at the limit of the stall or stalling. No matter how much your wing drops, you FIRST reduce the Angle of Attack until the stall warning stops and only then take care of everything else, including rolling the plane upright.

But what happens many times, almost always, in these stall accidents at low speed and altitude, is that the pilot tries to pick up the low wing with aileron and that causes an opposite yaw and more roll contrary to what you are commanding with the ailerons, with the plane rolling more and more and many times ending in a spin if you let the plane fully stall, which tends to happen when the pilot pulls up as a reaction to the nose going down do to the high bank. In short, if you are very slow (like if the stall warning is sounding) and your left wing and nose drop, don't try to pick up either (which is the very intuitive but very wrong thing to do, and what I suspect happened here). Instead, FIRST reduce the AoA, THEN correct the attitude.

[3WE]

***Because all of the above***

Plus an asymmetrical, airspeed-reducing wind gust…

[Gabriel]

***Because all of the above***

Plus an asymmetrical, airspeed-reducing wind gust…

Please explain.

[3WE]

***Because all of the above***

Plus a wind gust…

Please explain.

My interpretation of your Gabrillian-length discussion of numerous discrete, usually-parallel, sometimes-interacting mechanisms that conspire against aileron efficacy and roll control around stall conditions...

[Mechanisms in said discussion] makes a wind gust (except for one that adds some airspeed without significant roll disruption) that much more dangerous [i.e. relevant to the Beaver stall spin crash into water, therefore not burn, and luckily not-drown and die.]

Summary: I have added a lot of words, but not sure I improved the message.

Comprende?

[Gabriel]

Comprende?

Yes. What I called "the plane rolls itself due to an atmospheric disturbance" in my comment.

[3WE]

Comprende?

Yes. What I called "the plane rolls itself due to an atmospheric disturbance" in my comment.

Ok, I glaced back and didn't see it a second time.

Not_saying it's not_there, but...

Nothing really wrong with your discussion- a whole shit pot of words on aileron performance, and 5? on wind. Maybe the wind needs to be part of the final, summary statement: There appears to be wind in the video, the pilot blamed the wind and in-spite of the Don-Moore downwind factor the speakist cites, I'm thinking the wind is probably a major contributing factor, here.

Whatever the case, I will try to carry a few extra knots and stay closer to the water until I can build those knots when flying my armchair...I'd hope to do the same in an aeroplanie, but it's easier from here as opposed to there.

[Gabriel]

Ok, I glaced back and didn't see it a second time.

Not_saying it's not_there, but...

I don't blame you. It was some time since I last wrote something so unreadable. You are out of proficiency.

Nothing really wrong with your discussion- a whole shit pot of words on aileron performance, and 5? on wind. Maybe the wind needs to be part of the final, summary statement: There appears to be wind in the video, the pilot blamed the wind and in-spite of the Don-Moore downwind factor the speakist cites, I'm thinking the wind is probably a major contributing factor, here.

The wind may have been a factor, but he was already flying at a too high AoA and when the wing dropped he tried to pick it up applying about full opposite aileron (that much can be seen in the video), and most likely pulling up hard when the nose went down. Everything instinctive, everything incorrect.

Talking about wind being part of the final summary statement, well, it was part of the NTSB's probable cause. HORRIBLE probable cause:

"The pilot's failure tp maintain directional during the take-off in gusting wind conditions which resulted in the wing exceeding its critical angle of attack, a loss of control and impact with the water".

Can someone please explain the causal relationship between the failure to maintain directional control and the wing exceeding its critical AoA? I will not ask about the causal relationship between the failure to maintain directional control and the loss of control.

Whatever the case, I will try to carry a few extra knots and stay closer to the water until I can build those knots

Exactly. And if you get a negative wing gust, don't pull up. Especially don't pull up past the onset of the stall warning, never, including when you get a negative gust.
And if a wing drops around the stall, never pick try to pick it up with ailerons unless you reduce the AoA first. Never, including cases where the wing drop was partially induced by a side gust.

when flying my armchair...I'd hope to do the same in an aeroplanie, but it's easier from here as opposed to there.

It shouldn't be. You should either be proficient enough so as it is not more difficult there, or you should not be there in the first place.

[elaw]

Can someone please explain the causal relationship between the failure to maintain directional control and the wing exceeding its critical AoA? I will not ask about the causal relationship between the failure to maintain directional control and the loss of control.

I can think of a couple of ways that statement would make sense... and a bunch more where it would not_make sense.

First, the "directional control" they refer to could be about the pitch axis, as in mismanaging the plane's pitch vs. mismanaging its heading.

Or... they could be talking about an improper attempt to control the plane's heading with rudder instead of ailerons, resulting in a slip or skid, and in effect having one wing flying faster than the other. The "slower" one reaches too high an AoA and badness ensues.

[3WE]

You should either be proficient enough so as it is not more difficult there, or you should not be there in the first place.

Evan, while that is ideal, you need to be slightly less absolute...humans don't work that way in large numbers. /Friendly razz