Caravan Crash Credentials Connundrum

[3WE]

If they are going to discuss this, I suppose [not_italics]we should too.

https://pkbwl.gov.pl/wp-content/uploads ... RW_ENG.pdf

I’m with Bernty, it doesn’t look stalled, but I really don’t care if it’s stall or slip or inadequate pull up; a 60/70 degree bank is a lousy way to climb when you are low.

Great preliminary report with almost no information from the surviving pilot:

Why did he “hand over control”?

The trainee with a yoke and the trainee in row 2 ought to have some insight if the plane was malfunctioning or the instructor was having a health crisis or if the instructor just wanted to prove he could out do Gabe’s B-52 example?

[ocelot]

I would assume in the absence of other information that any handover was just part of the intended training schedule.

Meanwhile as for the accident itself, I'd tend to assume either something broke or it's another instance of inadequate roll authority at low speed. Doesn't seem entirely consistent with stalling one wing.

[Gabriel]

Meanwhile as for the accident itself, I'd tend to assume either something broke or it's another instance of inadequate roll authority at low speed. Doesn't seem entirely consistent with stalling one wing.

It is much more complicated than that. For now I will just say that "stalling one wing" almost never happens, and severe degradation of lateral-directional handling qualities (which is more than just "inadequate roll authority" as it also involves adverse yaw, adverse roll, and loss of roll damping) happens at high angles of attack even before a full stall (be it of one or both wings). So this accident can still be consistent with a stall-related situation.

Go there if you want to read my full dissertation on that.

[3WE]

***
Meanwhile as for the accident itself, I'd tend to assume either something broke
***

Yes, discussion!

The plane appears “locked” in a nice, gentle, unrelenting bank “INPUT”, which makes me concur that something broke or stuck with the ailerons.

A health crisis could be another cause which is why I was asking why they handed off the controls…or “my yoke is jammed, you try it”…

[ocelot]

It is much more complicated than that. For now I will just say that "stalling one wing" almost never happens, and severe degradation of lateral-directional handling qualities (which is more than just "inadequate roll authority" as it also involves adverse yaw, adverse roll, and loss of roll damping) happens at high angles of attack even before a full stall (be it of one or both wings). So this accident can still be consistent with a stall-related situation.

Dropping a wing because you stall one side first does happen. And regarding roll authority we were talking not that far back about another crash with similar appearances, where one of the things that came out was that the plane in question had limited roll authority at low speed. So if you yank it off the ground too early and then it starts rolling (because of crosswind or bad trim or whatever) you may not be able to counteract it.

Don't have the energy to visit there, sorry.

[Gabriel]

Dropping a wing because you stall one side first does happen.

Dropping a wing is a stall-related situation does happen... a lot.
That doesn't mean that one wing is stalled and the other is not.

[3WE]

Ok, Gabbiee, you are playing the "I know something you don't know game".

Quote = 3BS's mind (and I think Ocelot's, too):

Gee whiz, a spin is a pretty remarkable maneuver with a most-impressive, quickly-building roll rate...

It seems to make sense that you stall one wing while the other remains unstalled, thus providing that amazing drop, spinning motion.

Gabiee (paraphrased, not poetically):...

Well, ya know, it often isn't that one wing stalled and the other is not_stalled.

Ok, Mr. Hell-better aeroengineer, can you explain this in A nice, concise paragraph?

Before you do, I will outsider-ass-hat speculate on some stuff (and confess that you probably wrote a dissertation or two on this subject at this and the other forum.

So....

Maybe when you stall, you get into a situation where more-stalled = more drag and less lift. So, if you get some asymmetry going in your effective airspeed of each wing and AOA and your ailerons, etc, etc, etc....you have a situation where both wings are BASICALLY stalled, but the more stalled wing is dragging and producing less lift, while the less stalled wing is producing less drag and more lift....thus we get the remarkable twisting/spinning behaviour.

On the other hand, I remember that the wing angle vs the longitudinal axis of the plane is usually designed to lessen up as you move from the root to the tip...so THEORETICALLY you can get in a gentle stall and still have some aileron authority...

I dunno emoji.

Thoughts Ocelot?

[Gabriel]

There is no secret I am trying to hide here. And actually I wrote and deleted a response (by the magic of deleting your comment BEFORE submitting).

This was the exchange

Ocelot: Doesn't seem entirely consistent with stalling one wing.
Gabe: "stalling one wing" almost never happens.
Ocelot: Dropping a wing because you stall one side first does happen.
Gabe: Dropping a wing in a stall-related situation does happen... a lot. That doesn't mean that one wing is stalled and the other is not.

We may have just a semantics issue here. Stall is complex and has various definitions. And dropping a wing in a stall involves much more than the stall itself.

So I take back my responses to Ocelot by now.

Ocelot, please explain as precisely as you can what you mean when you say "stalling one wing" or "stalling one side first". Try to avoid using the word stall in your explanation.

[3WE]

Gabe: "stalling one wing" almost never happens.

I want to be clear: You are “taking this back”?

Because the outsider, ass-hat, parlour-talk understanding is that: A spin is a strong rapid rotation caused by one wing being basically stalled while the other wing is basically not_stalled.

(Yes, we must use the word “stall”.)

A stall is a rather sharp, significant loss of lift, caused by the sudden separation of smooth airflow across the top of the wing around the magical 16-degree +/- angle of attack.

I know you can add numerous (very numerous) caveats, but is this basically true, or basically wrong?

[Gabriel]

I want to be clear: You are “taking this back”?

Momentarily. Until I understand the "nuances" in Ocelot's thoughts.

A stall is a rather sharp, significant loss of lift, caused by the sudden separation of smooth airflow across the top of the wing around the magical 16-degree +/- angle of attack.

So this wing is not stalled?

On the other hand, I remember that the wing angle vs the longitudinal axis of the plane is usually designed to lessen up as you move from the root to the tip...so THEORETICALLY you can get in a gentle stall and still have some aileron authority...

[3WE]

So this wing is not stalled?

Lay off the absolute terms Evan.

172

Full power

Keep pulling the nose up

The nose-up attitude becomes pretty remarkable and terrifying for FOFFIES in 2A and 2F.

A nasty warning “horn” begins squeeling.

The horn pitch becomes higher as the squirrel senses death, there’s something of a thump and sudden sinking feeling, and the nose drops without input from the yoke. Vertical speed becomes negative.

That is a stall. (Spare me the nuances).

I can’t completely speak for Ocelot, but:

1. Ocelot said a spin is one stalled wing.

2. Gabriel, the hell-better aeroengineer, said no.

3. 3BS said, I thought Ocelot was right.

I have tried to reconcile this, but your replies are no comprende por tres caca de vaccas.

[Gabriel]

That is a stall. (Spare me the nuances).

Ok, that is ONE description of a stall. I'll go even further and say that that's the most common description of a stall.

In that sense, I agree that one wing can "stall" before the other.

But I will also say that (sorry if this a nuance), even without realizing, people don't talk in the same way about the whole plane stalling as they talk about one wing stalled, or one wing being more stalled than the other, or, as you did, about a "gentle" stall where you have parts of the wing stalled but you still have aileron authority.

So I am not sure that, when a wing "stalls" before the other in the sense of "stall" that you mentioned above, I would say that wing stalled before the other. With the definition "wing stall" that I use* (which also has nuances and is imperfect), when a wing drops when attempting a stall like the one you described, most likely both wings will be stalled.

As a side comment, I already commented here how once when practicing full stalls with the instructor in a C-152 (I was already a private pilot and was getting an endorsement in the C-152) I was pulling fully back on the yoke to the stops and I said "it doesn't want to stall" , to what my instructor replied "What do you mean? The nose is pointing up but you are like 2000 fpm down, you ARE stalled". Kinde of AF447 but a few decades earlier. And after I connected the dots (which took a couple more seconds) I didn't keep pulling up all the time. How does that fit in your "stall" definition?

I can’t completely speak for Ocelot, but:

1. Ocelot said a spin is one stalled wing.

Show me where. Wait, don't waist your time. He didn't say that. He didn't even say something that may be remotely interpreted as that.

2. Gabriel, the hell-better aeroengineer, said no.

I took that back.

3. 3BS said, I thought Ocelot was right.

So 3BS said that he thinks that what he thinks that Ocelot said, which is not what he said, was right. Talk about nuances.

* Angle of attack at which further increase of the angle of attack doesn't result in increased lift.

[3WE]

Nuances:

You choose to gloss over my inclusion of the word basically. It’s a gray concept that you and Evan struggle with, but kind of key nuance to this concept.

Ocelot did say wing drop. Acknowledged, she(as long as we’re claiming nuances), did not_say spin.

But again Evan, you stall a plane, and due several possible factors, a wing rapidly drops because it is basically/largely stalled and the other wing is basically/largely not_stalled, and you don’t do anything about it, you get a spin. Basically the same situation.

Final nuance- Ocelot basically said that she didn’t want to get into the nuances, but you had to go pontificating that there’s complexities- to the point of over stating and retracing statements.

My odds are basically 25% she rejoins this conversation.

[Not_Karl]

[Gabriel]

Nuances:

You choose to gloss over my inclusion of the word basically. It’s a gray concept that you and Evan struggle with, but kind of key nuance to this concept.

Ocelot did say wing drop. Acknowledged, she(as long as we’re claiming nuances), did not_say spin.

But again Evan, you stall a plane, and due several possible factors, a wing rapidly drops because it is basically/largely stalled and the other wing is basically/largely not_stalled, and you don’t do anything about it, you get a spin. Basically the same situation.

Final nuance- Ocelot basically said that she didn’t want to get into the nuances, but you had to go pontificating that there’s complexities- to the point of over stating and retracing statements.

My odds are basically 25% she rejoins this conversation.

Why do I have the feeling that you are being the black and white here? Like a stall is a stall is a stall?

Let's recap:

1- We had been discussing this topic there, where I made a too-long dissertation about stalls and "degradation of lateral control at high angles of attack at or close to stall". I provided some examples of planes that fail to recover from a bank even with full anti-bank aileron inputs. I brought the B-52 and I could have brought or many others. I mentioned there that a lateral control degradation in a stall situation was a possibility. Quoting myself: "I didn't say that the airplane stalled. I didn't even said that it likely stalled. I said that it is very possible that it did, as in what is seen in the video is not incompatible at all with a stall."

2- In the OP here, you put a link to the preliminary accident report. That report includes time-lapse photos of the take-off an initial wingtip contact with the ground. The phots show that when the wingtip contacted the ground the plane was in a 70 degrees bank and the pilot was pulling up hard (unfortunately I cannot clearly see the position of the ailerons and . You also brought the B-52 accident.

3- Ocelot said: "I'd tend to assume either something broke or it's another instance of inadequate roll authority at low speed. Doesn't seem entirely consistent with stalling one wing."

4- To which I replied: "It is much more complicated than that. For now I will just say that "stalling one wing" almost never happens, and severe degradation of lateral-directional handling qualities (which is more than just "inadequate roll authority" as it also involves adverse yaw, adverse roll, and loss of roll damping) happens at high angles of attack even before a full stall (be it of one or both wings). So this accident can still be consistent with a stall-related situation.."

5- This accident has nothing to do whatsoever with a sudden wing drop or with a spin. And yes in this point I am being quite black and white because it didn't. Like in there was no sudden wing drop and there was no spin. And no wing drop or spin had been mentioned so far.

6- For some reason, instead of focusing on the important stuff (everything that is highlighted in 4-) we all started to focus on the little bit not_highlighted in 4. And I took that little bit back.

What else do you want from me, Gata Flora?

[3WE]

Ocelot said: "I'd tend to assume either something broke or it's another instance of inadequate roll authority at low speed. Doesn't seem entirely consistent with stalling one wing."

Do you want to discuss this crash or stalling one wing?

If it’s THIS crash:

If a plane goes in in a 70 degree bank next to the ground (and you have no other information) us outsiders will ASK “wow, did they stall/spin the plane?”. Then we we go on to look for clues suggesting they did or didn’t. It’s a question, not a declaration.

My interpretation is that Ocelot watched the film and concluded that “it didn’t seem entirely consistent with stalling one wing.” (A speculative declaration based on video evidence).

That resonated with me because I saw the plane bank more and more in a gradually steepening bank.…the gradual bank increase is “not consistent with one wing being stalled.” (My speculative declaration based on the video)

Yeah, the plane could have stalled at some point when the bank got steep, but the slow development of the INITIAL bank is more suggestive of a something other than a stall.

Bottom line, we didn’t think it was a case of stalling one wing…

[Stall discussion]

But, for some reason Gabriel wants to question whether you can truly stall one wing or basically stall one wing and just exactly what a stall is (with the implication that Ocelot doesn’t have it quite right that you can basically stall one wing and 3BS has it wrong that a stall is basically a significant (not_total) loss of lift (and some other stuff) from the loss of smooth airflow over the wing, disrupted from exceeding the critical angle of attack.)

[Gabriel]

My interpretation is that Ocelot watched the film and concluded that “it didn’t seem entirely consistent with stalling one wing.” (A speculative declaration based on video evidence).

And I wholly agree with your interpretation of what Ocelot said, and with what Ocelot said if he said what we interpreted he said.

But, IF this accident was stall-related, it has more to do with severe degradation of lateral control in a stall situation (i.e. the bank angle increasing beyond the intended bank and/or being unable to pick up the wing by using ailerons), you know, like in the B-52 case that I brought up there and you brought up here, then the fact that that the video is inconsistent with stalling one wing (to which I agree) is irrelevant. The video, and furthermore the time-lapse photos in the accident report you linked, are consistent with severe degradation of lateral control in a stall situation ( consistent not meaning conclusive, it just means that it is not discarded by the evidence)

Yeah, the plane could have stalled at some point when the bank got steep, but the slow development of the INITIAL bank is more suggestive of a something other than a stall.

If you bank up to a certain point and pull up to close to stall AoA, you may very well find yourself in a situation where the bank keeps slowly increasing by itself and where anti-bank aileron inputs are ineffective to pick up the wing and can even increase the bank even further. You know, like in the B-52 crash.

Bottom line, we didn’t think it was a case of stalling one wing…

I think it is perfectly possible that it is stall related. Not necessarily "most likely". But what we see in the video and report doesn't make me think that it could not be stall related.

[Stall discussion]

But, for some reason Gabriel wants to question whether you can truly stall one wing or basically stall one wing and just exactly what a stall is (with the implication that Ocelot doesn’t have it quite right that you can basically stall one wing and 3BS has it wrong that a stall is basically a significant (not_total) loss of lift (and some other stuff) from the loss of smooth airflow over the wing, disrupted from exceeding the critical angle of attack.)

I took that back. Remember? It is definition-dependent. Let me ask you a question, Say that you are in a Tomahawk (it is more evident in low-wing planes that have a more evident dihedral angle) doing a sustained constant heading / constant track sideslip applying full left rudder and some right aileron, but you slowly inadvertently pull up as the speed decays. You get a stall warning but you continue slowly slowing down and pulling up. Eventually the plane enters a spin . Which way will the plane spin? Which wing is at a higher AoA? Which wing drops? Which wing stalls first?

I don't have a definitive answer to some of all 4 questions above, but I do have a definitive answer to 3 of them.

Here you have a real example of that happening (with a different T-tail plane):

https://www.youtube.com/watch?v=L2CsO-Vu7oc&t=2s

[3WE]

***Let me ask you a question***

***Say that you are in a Tomahawk***

***a real example of that happening (with a different T-tail plane)***

Let me give you an answer that will not_satisfy you:

If you follow THE spin procedure in the FCOM, OR follow a broad, fundamental “how-to-spin procedure” (Stall with crossed up controls), you tend to get a spin.

I don’t get what your point is.

I think you are still arguing with Boeing Bernty who didn’t think it was a spin because good pilots don’t get into inadvertent spins.

I think your point is: “sometimes they do”.

All that being said, you are comparing a dude who deliberately and authoritatively cranked into a 90 degree bank with a dude supposedly practicing a go-around which looked like a nice normal go-around except he slowly, but relentlessly rolled over to 70 degrees…

…where you need a lot of lift and where some pilots will lose altitude

and/or you pull up too much and stall.

I’m yelling that he seems to have a healthy energy status through 30 to 45 degrees of bank…I don’t see relentless pull ups…

The plane makes a continuous, slowly-increasing bank…

AFTER 45 DEGREES Whether he increases his pull up to stall OR pulls up gently and loses too much vertical lift, I don’t give a phugoid…

I don’t think it’s particularly analogous to “hold my beer, we’re doing a really steep, low-altitude turn in a B-52”. (And I’m avoiding absolute statements).

[3WE]

I think it is perfectly possible that it is stall related. Not necessarily "most likely". But what we see in the video and report doesn't make me think that it could not be stall related. And I’m really obsessed with stalls, near stalls, and subtitles that occur near stalls and have to point out over and over that it could be stall related, but you can’t call it a stall because it actually isn’t and even though we are all aware that speculation before the final report is speculative, I have to come behind every time someone speculates it isn’t a stall and point out that it could still be stall related, without being an actual stall, and the video alone does not conclusively prove or disprove any of it.

Fixed.

I think it is perfectly possible that it is micrometeorite related. Not necessarily "most likely". But what we see in the video and report doesn't make me think that it could not be micrometeorite related….

Yes, I can imagine slow speed and full power from the powerful PT-6 and the torque starts you turning and you slowly roll and you can’t/don’t correct for it…
not_unlike AA-191, but it’s still a bit too slow and smooth for a smaller airplane and looks more like a a gentle left bank input that for some reason is never removed.

What are the odds that Gabriel will say that torque basically isn’t torque and describe the nuances of propellor planes usually tending to turn left under high power and low speed?

[Gabriel]

I think it is perfectly possible that it is stall related. Not necessarily "most likely". But what we see in the video and report doesn't make me think that it could not be stall related. And I’m really obsessed with one of the top killers in GA which is actually preventable and where a good understanding can really make the difference.

Fixed.

Correct.

I think it is perfectly possible that it is micrometeorite related. Not necessarily "most likely". But what we see in the video and report doesn't make me think that it could not be micrometeorite related….

Are you serious? The plane was banking 70 degrees. That may be commanded or not. If commanded, it would be really crazy to do that immediately after lift-off. Especially when you are turning into the control tower, hangar, vehicles and playground area. Aslo the images in the report unequivocally shows the elevator deflected way up. And the video shows the tail "dragging" during the turn, as if the plane was at a high AoA. Yes, energy wise the speed seemed to be not anywhere close to the nominal stall speed. But in a level 70-degrees-bank turn (and this turn was quite level because it was skimming the ground which is quite level), the stall speed increases by 52%. And you can stall at any bank angle, pitch and speed if you pull up hard.

Conclusive? Not. I am sorry, I don't want to wait for the final report but the information we have is the information we have.
But meteoritical probability? Not either. It is a distinct possibility that this was stall / high-AoA related.
But it could have been other things like a mechanical issue, a health issue, or plain stupidity intentionally attempting this maneuver that was fully executed as intended. I just don't know. Do you?

What is your theory that is much more plausible than a stall or high-AoA related issue?
Because "looks more like a a gentle left bank input that for some reason is never removed", maybe, but it is not very helpful either.

I honestly don't understand what you expect from me.

[3WE]

Three people have said “they don’t think it’s a stall/spin”.

ZERO PEOPLE have said, IT ABSOLUTELY IS NOT A STALL/spin..

Then you say YOU THINK a stall spin is LESS likely.

So, I’m just not getting the ongoing lectures and counter arguments and corrections.

As to the question of what any of us knows, I already expressed my feelings there that there was very little information from the surviving pilots. Such information could be extremely insightful…”The yoke stuck, turned slightly left”. “The power cane up and it yawed and the stall horn sounded and they didn’t ease the nose down”. “Bob clutched his chest with one hand and pulled with the other while in pain.”

[Gabriel]

Three people have said “they don’t think it’s a stall/spin”.

ZERO PEOPLE have said, IT ABSOLUTELY IS NOT A STALL/spin..

Then you say YOU THINK a stall spin is LESS likely.

So, I’m just not getting the ongoing lectures and counter arguments and corrections.

As to the question of what any of us knows, I already expressed my feelings there that there was very little information from the surviving pilots. Such information could be extremely insightful…”The yoke stuck, turned slightly left”. “The power cane up and it yawed and the stall horn sounded and they didn’t ease the nose down”. “Bob clutched his chest with one hand and pulled with the other while in pain.”

You are making this waaaaayyyy to complicated, to the point that I don't know, Shirley, if you are being serious or trolling.

Let me take back ALL what I said in the thread and start from scratch.

Ocelot: Doesn't seem entirely consistent with stalling one wing.
Me: I 100% agree. However it is consisten with other stall-related things are are not stalling one wing.

Ok now?

[Not_Karl]

Daily Asshat.JPG (50.21 KiB) Viewed 421 times

[3WE]

1. I don't know, surely, if you are being serious OR trolling.

2. Ok now?

1a. Fixed.

1b. Don’t call me Shirley.

1c. I’m having the lasagna.

2. No, I still strongly support type-specific healthy airspeeds and attitudes as much as understanding stalls, stall warnings and the concept of proper, measured pitch inputs.

[3WE]

I thought that popcorn shortage thing was a a real article and only read the headline.

Upon further review, it is beautiful.

Please follow type-specific popping instructions- whether pop by wire or stove top.