Unusul Attitude Recovery

I am caught off guard by all the different way of teaching this. I always took the way I was taught as the only way, it was ever taught.

Makes me wonder what else I have been saying is procedure, when it is really just technique.


I wasn't taught this way. I was taught the APS way as well. I was also a career going pilot. Knowing what I know now, if I was a typical FBO private pilot with little proficiency I wouldn't want to add power ever in my typical VFR flying. The only reason I would be in a UA as a typical FBO private pilot would be sloppiness at altitude. The typical FBO private pilot are alert enough in the pattern not to dump it over unless they are flying stupidly or loose our engine. The only low altitude realistic scenario they should worry about is upsets in the flare where if they happened to get caught by the wind one day might bend a strut instead of pancake the aircraft. Keep in mind this person probably won't fly in over 15 knot winds and very little crosswind.

I just don't cannot come up with a scenario where (for the less proficient non-career PPL pilot) just getting them to instinctively yank the power could be real bad? Would you give some scenarios that are likely or even possible where pulling the power would result in an unrecoverable UA?

Thanks
 
Would you give some scenarios that are likely or even possible where pulling the power would result in an unrecoverable UA?

I may have conveyed the wrong message, but I don't think going full or idle power further pushes the pilot into an deeper unusual attitude.

I am all for full power/Idle, then power as needed, even if they are at full power for only a moment before backing it down to cruise power.
 
It doesn't raise the Critical AOA.

You're both actually correct on this; the reason for the apparent discrepancy is that you're assuming two different definitions of "relative wind." Mojo's is more in line with industry practice, which is to define "relative wind" to be the wind vector far enough ahead of the airplane to not be affected by the airplane's presence. Your usage of the term is what some industry people might refer to as a "local" relative wind. Even using the latter definition, you may still have some increase in the critical AoA based on a local increase in Reynold's number, due to the fact that the velocity of the air over the wing is going to be much faster than it should be based on the airspeed.
 
Even using the latter definition, you may still have some increase in the critical AoA based on a local increase in Reynold's number, due to the fact that the velocity of the air over the wing is going to be much faster than it should be based on the airspeed.

Yes but this application of increased critical AOA is as you pointed out from increased velocity will only be applicable to wing root out maybe a couple feet (prop size stipulating the effect). The rest of the aircrafts critical angle of attack remains unchanged. So if you took the mean critical angle of attack for that wing it might have gone from up a fraction of a degree, hardly worth mentioning.

The more dominant effects here and in any aircraft with straight line thrust and a conventional tail surface is going to be increased effectiveness of the elevator from prop wash as well as wing twist. This effect is what leads (at least I think), most people to say "oh critical angle of attack went up" when that increase is in practical purposes negligible. Wing twist for those that don't know is simply the wing root set at a higher angle of attack then the wing tip so if we keep the wing root from stalling with the application of power then we get maybe another degree or so of AOA before the rest of the wing starts to stall. This is why are power on stalls are so much more viscous, more of the wing is stalled then in the typical power off.

Again I am not denying the increase, but for practical understanding even at a CFI level, knowing how Reynolds number increases the critical AOA at the wing root (3 or 4 feet of a 20 foot wing) is even by my terms overly technical.
 
I may have conveyed the wrong message, but I don't think going full or idle power further pushes the pilot into an deeper unusual attitude.

I cannot come up with away that it can be worse to idle an engine in a UA or any way that this could make it worse so I completely agree with that.

As for full power, it plays tricks on many of our senses especially if disoriented. We feel a pull and a yaw/roll of the aircraft as well as a loud noise which would be a physiological nightmare if you already feel SD. Also the most necessary UA that would require power would be nose high at a low airspeed when engine effects would be greatest from adding full power. No doubt adding power is the optimal way to recover, but at altitude why bother because it also requires quick, swift, and most importantly proper control inputs to keep the aircraft from dropping a wing.

Take the new PPL with little extra training and have him in this situation when solo who gets spacial disoriented and would obviously be scared at first. If he/she instinctively adds full power because they saw nose high but are just a little too slow on the controls and the wing drops even a little we both know their next move will be turn away raising AOA on the low wing and almost certainly causing a more serious situation.

I believe at a PPL level that it is better to build your student with proper instincts. Feel a sink on final, I like to see an instinctive throttle response, get uncoordinated or in any danger in any maneuver pull the power and apply recovery action. The snap responses they make I don't think can be overly complicated or they will fail to make proper responses. I aim for a statistical safety factor, since statistically UA is not likely for VFR pilots and even more unlikely that it will occur at a lower altitude I teach pull the power since you have altitude you can use and aircraft control is easiest with power to idle. (My commercial students get Power, Pitch, Roll taught to them as they will be more proficient and better trained leaving them more likely to utilize such possibilities of a UA at a lower altitude)

I am not sure why we are arguing VFR UA though, does this often even happen? I personally cannot remember one accident report where a VFR pilot in VMC found him/herself in a UA, if anyone has some I would actually love to read them so link them up!
 
tail surface is going to be increased effectiveness ...This effect is what leads (at least I think), most people to say "oh critical angle of attack went up" when that increase is in practical purposes negligible.

The power on stall speed is markedly lower than power off speeds and increased elevator effectiveness cannot explain this. Part of this reduction will be due to a component of thrust supporting some of the weight of the airplane, but part will also be due the clmax-increasing effects mentioned.

Given that the root tends to stall first on most airplanes, anything that delays this effect will have the effect of reducing the stall speed.
 
In the AF we teach them quite a bit differently, it sounds like. Of course, our equipment is different (most GA guys aren't learning in a fully aerobatic and overpowered airplane), and our product is also different (most CFI's aren't preparing their students for solo aerobatics/formation flying). Still...

We teach three different VFR unusual attitude recoveries (Nose high, nose low, inverted) and two IFR recoveries (nose high, nose low).

VFR Nose high:
Max power for nose high recoveries, and add bank (rather than level the wings) to either 90 degrees of bank (slow speed) or inverted (usable airspeed). If you are slow, then as you get to 90 you can just let the nose slice down towards 0 pitch, or slightly below, level the wings, and fly out. If you are high speed, you can roll inverted, pull the nose to the horizon, roll wings level and fly out. The advantage adding bank, is that it gets the nose back down to the horizon quicker. Probably wouldn't help a GA non-aerobatics guy, but if you imagine the sort of unusual attitude you could get into from messed up aerobatics, you might get the idea.

VFR inverted: power as required, but probably mid-range, and push the stick to roll the aircraft towards the horizon the shorter distance.

VFR nose low: power as required... if airspeed is rapidly increasing to a high range, idle and speedbrakes may be required. If airspeed is near or below 1g stall speed, power to MAX may be required. Roll the shorter direction to the horizon and once bank is less than 90 begin pulling the nose up as you continue to roll towards wings level.

IFR nose high: same as VFR, except power as required, and don't increase bank angle above 90.

IFR nose low: same as VFR.

My favorite setup for the nose high VFR is to point the nose straight up and do 2 aileron rolls to disorient the student. They look all over the place and they can't find a horizon anywhere... I've had guys push the stick left, do a full aileron roll in the vertical, not see the horizon, and then push the stick right to start another full aileron roll in the vertical (but by that time we've basically started something like an ugly hammerhead, and it won't complete aileron roll #4).

For the nose low, I'll bring the nose up to 90 degrees nose high, let all the airspeed bleed off, and flip the airplane over to a mostly inverted, 50 or 60 degree nose low attitude. Students will be there at around 30 knots (with a stall speed of 80-90), and they'll STILL pull the power to idle because all they see is ground!
 
The power on stall speed is markedly lower than power off speeds and increased elevator effectiveness cannot explain this. Part of this reduction will be due to a component of thrust supporting some of the weight of the airplane, but part will also be due the clmax-increasing effects mentioned.

Given that the root tends to stall first on most airplanes, anything that delays this effect will have the effect of reducing the stall speed.

Agreed, the speed is in fact lower but the critical AOA is based on wing design and very minimally effected by the addition of power.

"Component of thrust..." I would be fine with this explanation as well as the marginal increase of critical AOA and change of local RW on the wing root with description of wing twist and so on. But to say critical AOA increases with power is (while true by a fraction of a degree on a technical level) is for practical purposes the wrong way to explain this.

PS ignore my elevator effectiveness part, that actually has nothing to do with this I don't know what I was thinking of. So I agree with you there too.
 
Agreed, the speed is in fact lower but the critical AOA is based on wing design and very minimally effected by the addition of power.

You're again confusing "local" AoA with the real AoA.

increase of critical AOA and change of local RW on the wing root with description of wing twist and so on.

This is exactly the same thing. You're just hung up on your non-standard definition of AoA.
 
You're again confusing "local" AoA with the real AoA.



This is exactly the same thing. You're just hung up on your non-standard definition of AoA.

Well unhang me up then? :)

Added: The only angle of attack I ever worked with was the one that originated from the string on a pole at the nose of the aircraft (not used now that some crazy designer put the damn engine there!) Which would put relative wind a few feet ahead of the aircraft.
 
Well unhang me up then?

By convention, AoA is measured with respect to the average chordline and the relative wind at *infinity* ahead of the airplane. The symbol used in most aerodynamics books is V∞. By definition, the propeller cannot change the relative wind.

Measuring the AoA in this way, a wing immersed in propwash will stall at a higher AoA than one that is not, because the change in airflow direction caused by the propeller is not seen when you take this high level, global view of the airplane. It's just magic.

Now, although there is nothing incorrect about this explanation, I do agree that it's not that useful, because it leaves out the "why", and answering the why requires a discussion of the local relative wind.
 
Now, although there is nothing incorrect about this explanation, I do agree that it's not that useful, because it leaves out the "why", and answering the why requires a discussion of the local relative wind.

If you agree with this because of the why, than I take it you agree for explaining AOA to a pilot it would be wrong to say that the power increases the AOA? It is, shall we say, overly technical and the student will likely walk away with the broad analysis that AOA increases as you increase power.
 
If you agree with this because of the why, than I take it you agree for explaining AOA to a pilot it would be wrong to say that the power increases the AOA? It is, shall we say, overly technical and the student will likely walk away with the broad analysis that AOA increases as you increase power.

Assuming the aircraft is trimmed for level flight, an increase in power will increase the pitch, which increases the AOA, right?
 
AOA to a pilot it would be wrong to say that the power increases the [critical] AOA?

I don't agree that it's wrong, for the reasons I went into, but I agree that this explanation alone is less useful than explaining about the local relative wind.
 
Assuming the aircraft is trimmed for level flight, an increase in power will increase the pitch, which increases the AOA, right?

Not really. Pitch is equal to climb angle + AoA. For the perfect airplane, adding power will merely cause the airplane to climb at the trimmed AoA. The increased pitch is due to the increased climb angle, not an increased AoA.

On real airplanes, the propeller slipstream may well impinge on the horizontal stabilizer, which essentially retrims the aircraft to a higher AoA, just as if you pulled back on the yoke a bit. That's why on a Cessna, after adding power, you may end up going slower, rather than faster.

Or, the thrustline of the engine might lie above the CG of the airplane, where adding thrust causes a reduction in AoA and thus an increase in velocity. Personally, I haven't seen this effect, although I understand it occurs on some jets.
 
Assuming the aircraft is trimmed for level flight, an increase in power will increase the pitch, which increases the AOA, right?


Haha I am assuming this was a joke right? Seemed to go well with "student...increase power = increase AOA"
 
Haha I am assuming this was a joke right? Seemed to go well with "student...increase power = increase AOA"


Not a joke, just an observation where it seems to change the angle of attack, all other things being equal. There are things that should happen, and then things that actually happen based on the characteristics of the airplane, just as in tgrayson's example. That leads to a load of confusion, CFI or not.

I have a basic, elementary understanding of aerodynamics that I have learned based on FAA pubs and what I was taught, which from what I understand, are both wrong in a lot of instances. I would guess that the aerodynamic knowledge tgrayson has is probably more than 99% of other CFIs.

There seems to be debate against those who are 100x more knowledgeable than me on these subjects, so how are people like me supposed to sort through it all? The only way we are able to is by the direct observation we get everyday. It may be fundamentally flawed, or it may be a phenomenon specific to the aircraft we are limited to, but it is hard to disagree with something we see everyday.

Does this make sense? I know it was a bit of a ramble, but I am trying to give you an idea of where I am coming from and where students (I still consider myself a student) are coming from.
 
Not a joke, just an observation where it seems to change the angle of attack, all other things being equal. There are things that should happen, and then things that actually happen based on the characteristics of the airplane, just as in tgrayson's example. That leads to a load of confusion, CFI or not.

I have a basic, elementary understanding of aerodynamics that I have learned based on FAA pubs and what I was taught, which from what I understand, are both wrong in a lot of instances. I would guess that the aerodynamic knowledge tgrayson has is probably more than 99% of other CFIs.

There seems to be debate against those who are 100x more knowledgeable than me on these subjects, so how are people like me supposed to sort through it all? The only way we are able to is by the direct observation we get everyday. It may be fundamentally flawed, or it may be a phenomenon specific to the aircraft we are limited to, but it is hard to disagree with something we see everyday.

Does this make sense? I know it was a bit of a ramble, but I am trying to give you an idea of where I am coming from and where students (I still consider myself a student) are coming from.

Hey I am sorry then I didn't mean to throw that in your face. I took it as a joke based on what I wrote and don't worry about rambling I ramble with the best of em!

As for the aerodynamics, "from FAA and what people told me" all i can say is *cringe*. Most pilots understanding of aerodynamics is extremely flawed and yes tgray has an incredible knowledge for that stuff far beyond what I think a pilot needs (but it can never hurt).

However if you are interested in this stuff read that book I mentioned in my other post "Emergency Maneuver Training" by Rich Stowell.

That book has a better explanation and gives a better practical understanding of aerodynamics than any book I have ever seen. It is all in layman's terms with I think one or two mathematical formulas (which can be ignored) in the entire book. It explains aerodynamics in the beginning, then explains how they relate to each control surface and finally how they effect the aircraft through various maneuvers and emergencies. Definitely a must for the pilot trying to learn about this aerodynamics stuff.

To further explain tgrayson and hopefully make it easier to understand, if you take up a Seminole and set the aircraft trimmed for cruise at say 120 knots. The Seminole has a T-tail and is a twin so thrust over the tail is minimal making the aircraft perform a little more like tgrayson explained as "the perfect aircraft." First before we continue here are some definitions that you will need to understand what is happening:


Trim - The trim for all practical purposes sets your aircrafts speed (irregardless of power) and for a technical purpose it sets an angle of attack. AOA always corresponds with a speed and that speed will remain the same at that given AOA (in a perfect airplane) no matter what the power setting is.

Relative Wind - Also for practical purposes we can ignore infinite RW as tgrayson was speaking of and simply look at the local relative wind or just call it relative wind, it is what you have dealt with your entire career. For a practical definition, relative wind is the wind flowing opposite your direction of flight (remember 3D environment so ignore up down left and right, they do not exist).

Angle of Attack - To repeat one last definition, AOA is the angle between RW and the chord line of the wing. The chord line is simply a straight line from the leading to the trailing edge of the wing.



Now we are back in our Seminole with a practical understanding of AOA, RW, and trim. We are set up for 120 knots at about half throttle if you reduce the throttle here is what happens. The aircraft lets say is flying at 5 degrees angle of attack because that is what you set with your trim. The aircraft will start to slow, your flight path currently still level, but now because it slows down it is starting to loose its angle of attack in level flight. Well remember trim has your AOA set for 5 degrees so to keep 5 degrees the aircraft will nose down picking keeping its speed at 120 knots nosing down as much as it has to. Remember, RW is the air flowing opposite your flight path; so thinking that you see your flight path is now a descent and the relative wind is coming up at you the same way it did in level flight. To see this look straight out with your eyes and remember at level you saw the horizon right out in front of you and now if you stare straight out you are looking at some point on the ground, so you can see your flight path has changed.

You are in a descent the aircraft has realigned itself with the new RW and has remained at its 5 degree angle of attack. You can do the exact opposite adding power and the process will repeat in reverse until the aircraft aims at whatever degree pitch up it needs to hold 120 knots.

So the Seminole will fly much like a perfect aircraft because the horizontal tail is not subject to thrust from the engine. This engine thrust is what tgrayson was talking about for your single engine centerline thrust aircraft. They blow air back over the tail, as you know, the faster you go the more effective your controls are and the slower (slow flight especially) the sloppier your controls. So for a single engine trainer if you set say 100 knots at half power cruise in a C172 then go full power you will climb at about 90 knots. The increase in angle of attack happens because the thrust from the engine blowing over the elevator makes it more sensitive causing the AOA to change slightly higher setting a slightly lower airspeed.

Tgrayson - I know some of these things are slightly off of "technical" truth and I have purposely omitted certain effects for simplicity. But if looked at for practical purpose and pilot understanding, I believe they more then suffice. So be gentle with your technical corrections please :)
 
so how are people like me supposed to sort through it all?

No way, really. The main problem is that there is a vast chasm between those who produce aerodynamic literature and those who produce pilot training material. The former very rarely explain how to apply theory to what pilots actually do in the aircraft, and the latter garble the aerodynamics. It took me years to figure out how to connect the two and it occurred on a piecemeal basis. I used to lay awake at night thinking about it.

I don't think an instructor needs to be able to explain *everything* an airplane does (I can't), but I do think there are some broad, organizing ideas that are the seeds around which all airplane knowledge forms. Not being able to communicate these to a student can provide them with a serious impediment to understanding airplane flight. I encapsulated those ideas in my "Core Concepts" link.

Take, for instance, the idea that AoA controls airspeed. If you accept that as an foundational principle (and you should), then you would know that an airplane in climbing flight at 75 knots has the same AoA as an airplane in level flight at 75 knots and the same AoA as a descending airplane at 75 knots. This would hopefully remove evermore the idea that the pitch attitude was a reliable guide to AoA, since all three airplanes would have different attitudes.

What this shows is that to some extent, we need to interpret our experience in light of theory, not theory in light of experience. Now, I know this sounds like the cynical "If the facts don't conform to the theory, get new facts," but it's not really. The reality is that you and I aren't going to find any flaws in underpinnings of aeronautical science; if we think we have, it's probably because we don't understand the science well enough.

For instance, a former CFI student of mine came back from a flight with a student and confronted me with the fact that they were in slow flight, behind the power curve, and pulled back slightly on the yoke and the airplane entered a sustained climb, which I had told him was not possible. I laughed and pointed out that he had gotten his reasoning backwards; the fact that they entered a sustained climb after slowing down showed that they were never behind the power curve in the first place. The characteristics I had given him about being behind the power curve were true by definition, so he needed to start with that truth and work backwards to question what he was witnessing.
 
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