Impossible Turn Tested at Altitude

Henning said:
You do stall, and start a spin, that's why you have to immediately unload the wing pretty much immediately. You're yanking back as hard as you can to transfer the energy impact to the highest ballistic arc you can
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Pulling 3 G's isn't going to get you "the highest ballistic arc", it's going to get you stalled. To transfer the energy into that ballistic arc, you'd have to be pulling the aforementioned 1.6 G's.

In addition, you probably want slightly less than the maximum because by pulling the maximum non-stall G's you're going to be giving some of your energy up to excessive induced drag. So maybe a smooth 1.5G pull... But definitely not 3.
 
Henning said:
:confused: The Mooneys I flew typically beat 1200-1500fpm on takeoff. I imagine the big bores do better.
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M20C isn't a big bore - It's an O-360 at 180hp.

AFTER the first 20 seconds or so you can get great climb rates, but the first 20 seconds or so, getting sped up and getting the gear and flaps up, aren't so great.
 
flyingcheesehead said:
M20C isn't a big bore - It's an O-360 at 180hp.

AFTER the first 20 seconds or so you can get great climb rates, but the first 20 seconds or so, getting sped up and getting the gear and flaps up, aren't so great.
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Ah, 26 seconds after power up, I was thinking lift off for take off.
 
flyingcheesehead said:
True - But not the one you're thinking of. Minimum turn radius is just above stall speed *for the bank angle used*. So if we look at the common C172N (Vy= 73 KCAS, Vg = 66 KCAS, Vs1 = 50 KCAS), If we're starting at Vy, we're at 1.46Vs1, a 60-degree bank will have us stalling at 1.414Vs1 or 71 knots
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Those increase in stall speeds are based on a constant altitude turn- loading up the wing.
You don't hold the nose up as you initiate the bank- you simultaneously pitch the nose down as you roll into the bank.
Indicated speeds are only an initial guide anyway, to get started training and learning the feel.
It's all about the feel. You should practice at altitude steep gliding turns just above and into the stall so you have the feel.
You won't be looking at airspeed anyway, your focus will be on the terrain environment judging your turn rate to see if you're gonna make it to the runway or if you have to roll out and accept another part of the airport environment which is also a factor in making the turn around.
I keep saying it is a good tool - "when appropriate".
Many things to consider when making that decision.
Many more than I have mentioned, but stalls are all about feel- not calculated airspeed numbers.
 
nosehair said:
Those increase in stall speeds are based on a constant altitude turn- loading up the wing.
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No they're not, there's based on constant lift coefficient at stall AOA (a good assumption) and dynamic pressure varying with the square of airspeed. With a 1g stall speed (lift = weight) of 58 mph, the stall speed with enough lift for 3g (lift - 3*weight) will be sqrt(3)*58 or ~100 mph. Bank angle doesn't matter, if your 1g stall speed is 58 mph you don't have 3g available below 100 mph at any bank angle.

Nauga,
and his doghouse plot
 
SixPapaCharlie said:
That rope didn't break, he released it
Thus the instant reaction.
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His instructor probably released it. The reaction is quick because there is no doubt about what's happened, and the response is preprogrammed, and discussed before take off. From 200' that glider can easily turn back and will probably need full spoilers to get down. From 700' he could probably fly a normal pattern. Glider pilots train for this, possibly because ropes break more often than engines fail. But I don't see any reason why power pilots shouldn't train for it too.
 
nauga said:
No they're not, there's based on constant lift coefficient at stall AOA (a good assumption) and dynamic pressure varying with the square of airspeed. With a 1g stall speed (lift = weight) of 58 mph, the stall speed with enough lift for 3g (lift - 3*weight) will be sqrt(3)*58 or ~100 mph. Bank angle doesn't matter, if your 1g stall speed is 58 mph you don't have 3g available below 100 mph at any bank angle.

Nauga,
and his doghouse plot
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I don't really understand your response. I think my term "constant altitude" may be misleading. A more accurate term would be "increasing g forces, as in pulling 2 g's at a 60° bank. The common term "constant altitude" and bank angle stall speeds comes straight from the Airplane Flying Handbook.
Yes, if you pull 3 g's during your gliding turn, your stall speed is increased- whether you're turning, level, gliding, climbing, whatever.
Just don't do that. The only way to stall an airplane is to pull back on the yoke.
Just don't do that. Excessively. That's why I said to practice the feel.
Learn to feel the controls approaching the stall in all possible configurations- as we are supposed to do in training for the Private Pilot Certificate as is outlined in the Airplane Flying Handbook.
The PTS does not test on accelerated or cross-control stalls, but the AFH does and all instructors and pilot trainees are supposed to be proficient in all maneuvers in that book.
 
Just a data point...

...I don't recall ever having done "The Impossible Turn" scenario.

Maybe in the distant past I was shown it, but that was mainly to show what a bad idea it was.

I also don't think I've ever made a point of demonstrating one, except perhaps, again, to reinforce that its a BAD idea and not to be considered as an immediate consideration. What I wanted to see was a turn of not more than about 45º to select the least bad spot to land the plane under control. Only then, with sufficient altitude and things calmed down, to maybe consider a medium turn back towards the airport environment.

I'm not saying that that is right or wrong, just my recollection as a pilot trained in the 1970's.
 
Henning said:
Ah, 26 seconds after power up, I was thinking lift off for take off.
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No, it was 26 seconds after rotation.

But, while I can easily climb 1000 fpm in the Ovation (the other day I was getting 1300fpm at 140 KIAS!), I think the first 500 feet takes well over 30 seconds - I lift the nose at 70 knots and fly off shortly thereafter, accelerate to 85 for the initial climb, retract the gear, accelerate to 95-100, retract the flaps, Vy is 105 KIAS clean. But I usually don't stay at Vy for more than a few seconds before accelerating to at least the book-recommended cruise climb of 120 KIAS or the most efficient cruise climb of 138 KIAS.

Climb performance is excellent, once you get to the higher speeds - But it takes time to get there, you don't just pop off the ground at 1000 fpm so I think it's safe to say that he's at 500 feet or less in the video.
 
nosehair said:
Those increase in stall speeds are based on a constant altitude turn- loading up the wing.
You don't hold the nose up as you initiate the bank- you simultaneously pitch the nose down as you roll into the bank.
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I was commenting on Henning's technique - With NO bank, you can't pull anywhere close to 3 G's at Vy in a Citabria.

Also, regarding your point about a "constant altitude" turn above - That's not entirely true. "Vertically unaccelerated" would be more correct. A 45-degree bank at a constant 500 fpm descent (or climb) increases the stall speed exactly the same way it does in a level turn. If you unload the wing in a turn to reduce the load factor and thus also reduce the stall speed, you will introduce a downward acceleration. You'll also decrease your rate of turn and thus increase your turn radius, which is kind of the point here. ;) But I'm sure you knew all that already.
 
FastEddieB said:
For the most part, I'm not sure training for The Impossible Turn increases a pilot's chance of surviving one, at least with the level of training most GA pilots get.
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Yes, and that is my point. The level of training most GA pilots receive is inadequate. Which is why most pilots who attempt this maneuver are not successful.

I do it routinely and successfully only because my old CFI taught me.

We have become a culture of pilots trained only to the minimum standards of the PTS since it's inception.
Before the PTS, we were subject to being tested on any maneuver in the AFH. The Impossible Turn is not in there, but accelerated stalls, cross-control stalls, & power-off approaches from 90°, 180°, & 360° are, and that goes a long way towards the level of proficiency I am trying to promote.
 
nosehair said:
I don't really understand your response.
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My point was that a 3g pull as described earlier is not possible under the conditions described. That was all.

Nauga,
and his V-n diagram
 
Much of the discussion is based on straight-out departures. What about other than straight-out departures? Any rules of thumb? Say, something like 800' AGL left X-wind in a typical 172. Do you make a 270* to the right return? Or continue left/right turns to line up? Or look straight ahead for a field?
 
woodchucker said:
Much of the discussion is based on straight-out departures. What about other than straight-out departures? Any rules of thumb? Say, something like 800' AGL left X-wind in a typical 172. Do you make a 270* to the right return? Or continue left/right turns to line up? Or look straight ahead for a field?
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Here, my inclination would be to make a 90° left turn in that case, back towards the runway environment. From 800' there might even be enough time and altitude to fly a very abbreviated pattern to land part way down the runway into the wind, rather than to find oneself way too high to land downwind.

It seems to me the right 270° would chew up a lot of altitude and could leave one coming up short.

But of course a lot depends on the runway length and other runway/taxiway/grass area options. And I'd try to be alert to good off-airport options as well.

Good question, though.
 
OK, I'll get some fresh hot popcorn and a cold beer and watch while you heroes actually have someone cut the mixture without warning and you fly the impossible turn.
Should be better than watching a demolition derby at the fairgrounds.

If you try the impossible turn you will die. It IS just that simple.

It is like you going to Vegas believing you will beat the house at craps.
Once in a while someone does (and the house will advertise that to the high heavens) while 99 and 44/100ths percent of the rest of the suckers who believe the advertising will shoot craps and go home broke.

So the question is, do you feel lucky, punk?

edit: oh yeah, and the impossible turn does not refer to 800 feet with a 90 degree turn
 
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SixPapaCharlie said:
Right. That's what I did (half flaps, climb at Vy). The point of the exercize was well one, to go flying and do something but also find out what my min was.

People throw around 1000 feet AGL. I now know that would have killed me.
I had to do 180, then an additional 45 then an additional 45 back to line up.

I think I did everything the way I was supposed to.
I really don't think it was silly to do this.
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Maybe it's not you, maybe it's the aircraft you're flying that 1,000ft would be insufficient for. Think about trying it in a different airplane?
 
FastEddieB said:
Here, my inclination would be to make a 90° left turn in that case, back towards the runway environment. From 800' there might even be enough time and altitude to fly a very abbreviated pattern to land part way down the runway into the wind, rather than to find oneself way too high to land downwind.

It seems to me the right 270° would chew up a lot of altitude and could leave one coming up short.

But of course a lot depends on the runway length and other runway/taxiway/grass area options. And I'd try to be alert to good off-airport options as well.
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A lot depends on the wind. If you have a reasonably strong (10+ knot) headwind on takeoff, it might be better to chew up that altitude in the right 270 because you're going to be downwind on final - If you were climbing at Vy, chances are you didn't leave much runway behind you and your climb gradient will have been higher than the descent gradient.

If the airport has a crosswind runway, I might try making my left crosswind departure into a downwind for that runway, but I don't think I'd try making a full pattern to the runway I departed from unless I had a lot of spare energy.
 
I remember trying this in a C182 with a CFI a few years ago to see what was possible. I aggressively pushed the nose down and did about 50-60 degrees of bank. We made the 180 in a few seconds, but lost about 600 feet of altitude (if I remember right).
 
The Navy did a study on this maneuver and found 45° to be the optimum bank angle, which has also been my experience.
 
nosehair said:
The Navy did a study on this maneuver and found 45° to be the optimum bank angle, which has also been my experience.
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What people seem to be missing out of Dr. Rogers' papers is that the 45 deg bank and close to stall speed/AOA is that he assumes steady-state for much of his analysis with no dynamic transitions between phases of the maneuver. There have been studies published since that show the transients and the dynamic nature of recognition, recovery, and maneuvering since he published the 'impossible turn' paper that show that their is a lot of sensitivity to things like reaction time, entry speed, winds, aero performance variations, etc, so a blanket '45 deg and hope for the best' might be easy to remember but it's far from optimal for the whole maneuver.

Also note that while Dr. Rogers was a professor at the USNA when he published his research and a couple of his students expanded on it, it was not a "Navy study".

In the interest of full disclosure, I have corresponded with Dr. Rogers on this material and met with him face to face in Annapolis to talk about how to refine it. I also published my own results through AIAA as well.

Nauga,
with a bang and then silence
 
I am very interested in what you learned. Seriously.
I did not mean to imply "45° and hope for the best".
Clearly, the maneuver requires training. Much training- not just once or twice- or or even 5 or 10 times. Every pilot who tries and fails has not practiced enough.
Did you or anyone become proficient at stalls or landings or steep turns or whatever in a few quick tries. No, of course not.
Do it until you are proficient at it.
I did. That's all I can say about it.
 
nosehair said:
I am very interested in what you learned.
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I'll dig it up and summarize in a bit.
nosehair said:
Clearly, the maneuver requires training. Much training- not just once or twice- or or even 5 or 10 times.
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You might be surprised to find that I agree with you. I'm not suggesting that returning to the runway is the best option, but I'm also not a fan of leaving performance or capability back on the ground. We think (almost) nothing of someone who suggests going out and shooting instrument approaches when it's 800/1 with tops at 5k but that's suicidal for someone who's not proficient in IMC. When someone suggests an EP that requires this level of proficiency, however, the loudest response seems to be 'NEVER!' Like flight in IMC, It might not be for everyone; and it most definitely requires proficiency, skill, and an understanding of the techniques and variations with conditions, but it's definitely an option for those who choose to be proficient. It is NOT an option if you're not proficient or outside of parameters for your airplane or conditions, and if it's in your plan it's a decision that should be made on the ground, not in the air when things go bad.

Nauga,
who wouldn't do anything close without an AOA gauge
 
nauga said:
who wouldn't do anything close without an AOA gauge
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AoA's - Don't leave home without one.

They make it quite easy to take it right to the edge and add a cushion to the turn. It's still up to the pilot to recognize whether or not he's in the window.
 
I don't know how we can expect proficiency in any maneuver we cannot practice? Approaches are practiced all the time to minimums or beyond without anyone getting excited. I don't know a single instructor that would demonstrate or ask a student to do a turn back real world (close to the ground). Let alone do it repeticiously. How many non-acro pilots are even proficient at a 45 degree power off turning stall?

Point is the majority of pilots on this board are never going to be proficient in this maneuver even when practicing at a safe altitude so the whole "turnback" argument is just adding doubt to people's minds about what to do in an emergency and perhaps making them less safe.
 
Alexb2000 said:
I don't know how we can expect proficiency in any maneuver we cannot practice?
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I don't either - If you want turning back as an option I suggest finding a way to practice within your personal bounds for safety. If you aren't proficient or, then don't try it when the real emergency pops up. It really isn't mandatory and there are any number of ways to add a 'pad' for safety or lack of precision. The best time to learn them is not when the engine pukes at 500-600-800-1000 ft AGL.

Alexb2000 said:
Point is the majority of pilots on this board are never going to be proficient in this maneuver...
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Then they should not attempt it. There are also a lot of pilots on this board who are not proficient at flight in IMC, but there isn't a great call to suppress practicing it. Quite the opposite when done safely, by my observation.

Nauga,
and his engine-out footprint
 
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nauga said:
I don't either - If you want turning back as an option I suggest finding a way to practice within your personal bounds for safety. If you aren't proficient or, then don't try it when the real emergency pops up. It really isn't mandatory and there are any number of ways to add a 'pad' for safety or lack of precision. The best time to learn them is not when the engine pukes at 500-600-800-1000 ft AGL.

Then they should not attempt it.

Nauga,
and his engine-out footprint
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So do you practice these close to the ground? Do you do 45 degree turning stalls? In other words what do you recommend as a training regime?
 
Nauga, thanks for the repeat of the need for the training. And you are right about most pilots not being able to find an instructor who is proficient at this maneuver , much like stall/spin training. We have become a culture proficient only in the rote PTS items.
I blame it on the federal government for stopping testing on overall proficiency, and only testing rote PTS proficiency.
People tend to think that if it was important, it would be tested.
Instructors are going to teach what is tested.

On another point. Your BEST AOA indicator is in the feel in your hands and feet, the sound in your ears, correlated with the sight picture in your eyes.
In light airplanes. This discussion does not extend to heavy airplanes, where an AOA indicator would be more reliable.
 
Alexb2000 said:
So do you practice these close to the ground? Do you do 45 degree turning stalls? In other words what do you recommend as a training regime?
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I wouldn't describe myself as proficient in anything close to a return to the runway right now for lack of currency and I would not consider it in an airplane without an AOA indicator. When I have been current it has been with considerable pad over the 'optimal' technique to allow for mistakes. I do not practice below pattern altitude. I am comfortable with accelerated stalls well in excess of 45 deg bank, normal, uncoordinated, and with aggravating inputs; and recoveries from same. I am not an instructor and have no desire to recommend a training regime for anyone.

Nauga,
who almost forgot :D
 
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We have lots of active instructors and skilled pilots on this board. If no one currently teaches this technique, or can even quantify training beyond "just doing what an individual is comfortable with". Then I'll go back to saying this topic is nothing but dangerous for newer pilots and a cop out by anyone recommending it.

We all need to remember, people read and believe this stuff. Theoretical crap that everyone is scared to demonstrate even in practice, when all they have to do is push the throttle in to recover, just has no place here IMO.

I'll drop it now.
 
Start at 2-3000 feet, whatever you're comfortable with. Line up with a road/power line or something you can reverse course and re-align with. Full power Vy, cut the power, nose over to the attitude you know will result in a best glide speed. You may need to refresh on that attitude first because you don't want to waste time looking at the airspeed, and it will be slow catching up with the pitch change anyway.
As you pitch over, sharply roll into a 45° bank - by outside reference only. You may need to practice outside reference with the attitude indicator first, but the goal is to be able to pitch and roll by outside reference only.
Start with the altimeter needle on a hard number so you can see how much altitude you lose during the turn around and re-alignment.
Each time you practice, you will probably lose a little less altitude.
When you are comfortable that you won't stall, start practicing at a lower altitude until you are comfortable trying it at, say, 1000'. Climb out from a runway and try it at 1000'.
Depending on the airplane, you should be able to get down a bit lower.
The normal turn to crosswind is at 700agl (AIM recommended).
That would be a reasonable goal, to start the crosswind turn, cut the power and continue around for a return to the runway.
There are many variables to consider and practice for. In a crosswind you would turn into the wind. Other possible off-airport landing spots may influence your direction of turn.
Strong headwinds may cause you to be to high with a quick turn, so you may want to increase turn radius or S-turn to get low, especially with a tailwind.
You will need to have a very isolated no traffic airport to do these shenanigans, and you may not get back around to the actual runway, but there may be a better spot at the 90 to 135° area.
I think we are all better than just taking what is in front or within 30°.
Certainly if it is downtown or a housing community.
It is our responsibility.
 
nosehair said:
Your BEST AOA indicator is in the feel in your hands and feet, the sound in your ears, correlated with the sight picture in your eyes.
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Seriously? You're going to right up to the ragged edge of the envelope in a minimum altitude, maximum performance turn based only upon what you're feeling in hour hands and feet and hearing with your ears? That may be fine for the experienced Ag pilots among us; but, for the rest of the pilot pool, there's a very high likelihood that we're either going to over or under estimate our energy status - either way with potentially fatal results - the accident statistics bear me out.

I'm a proponent of enhanced stick and rudder skills through training. All fixed-wing pilots would benefit from basis aerobatic skills. But, in my opinion, the average private pilot who flies 50 hours per year, ought to consider all of this talk about how to safely make the "impossible turn" theoretical in nature.
 
Alexb2000 said:
We have lots of active instructors and skilled pilots on this board. If no one currently teaches this technique, or can even quantify training beyond "just doing what an individual is comfortable with". Then I'll go back to saying this topic is nothing but dangerous for newer pilots and a cop out by anyone recommending it.

We all need to remember, people read and believe this stuff. Theoretical crap that everyone is scared to demonstrate even in practice, when all they have to do is push the throttle in to recover, just has no place here IMO.

I'll drop it now.
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And for the record I will state again, I was not going out to teach myself how to turn back 180 on an engine out.

I was simply determining with my given plane, skills, and the conditions, how much altitude would I personally need to make that decision.

People do read and believe this stuff and from reading forums, the "rule" that gets tossed around is 1000 AGL. I know now I can't say Ok, 1000 AGL, I am turning back.

People reading and believing also need not say "1000 feet, I am safe to do this".

I will continue to practice this maneuver at alt. until I have the reflexes of the young man in the glider (sorry I misunderstood what was going on in that clip by the way. Nice work)

For me in my plane, the 1000 ft rule is not going to work at this point I have proven it.
 
According to what I've been taught, altitude is not the only issue. You also need to know whether your climb angle is larger or smaller than your descent angle.
 
Every time this thread and topic come up I truly wish more folks would do the sailplane add-on rating. You will find that the experience of flying minimum sink in a thermal with a steep bank will cross over to heavier aircraft just fine. Yes, you'll need to practice in the heavier aircraft, but your brain and reactions are better prepped to learn after you've been "engine out" from before the takeoff roll to landing. On purpose.
 
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