Testing the Impossible Turn

mantakos said:
The number "62" appears nowhere in that report.
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Based on Rich's statement in item #2 of post #16, it looks like he calculated an average of several of the scenarios from the simulator study. Rich had an article in Aviation Safety which confirms this (in one of the sidebars):

http://www.aviationsafetymagazine.com/newspics/pdfs/26-1-In.pdf

If you take the total number of successes for all the sorties shown in that sidebar, and divide it by the total number of attempts, the result is a 62% success rate. Since that involves a number of different scenarios, and is de facto weighted toward the scenarios with the larger number of attempts, I'm not sure why Rich felt that this average was useful.

Neither does the number "68".
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From the same sidebar, doing the same calculation for the sorties that involved telling the pilot what technique to use (the right-hand four columns) yields 67.5% (68% when rounded off).

Again, this is an average of various scenarios, so I'm not sure how significant it is.

It's interesting that with a 30 degree banked coordinated turn, the success rate went up to 95% on the first attempt, vs. 75% for a 45 degree bank. Presumably this is because the steeper bank angle is harder to do correctly.

Subscribers to Aviation Safety can view the complete article here:

http://www.aviationsafetymagazine.com/issues/26_1/features/8137-1.html
 
dmccormack said:
So if I'm 3000' AGL I should land straight ahead?

:rolleyes:

There is an altitude which provides sufficient energy to manuever for a landing. The FAA gives us 1000' AGL for 180 power off for the Commercial PTS -- and that's heading away from the landing point when the exercises begins (In other words -- you have to do a gliding 180)

The question is -- what altitude for this airplane changes the emergency response from "Land straight ahead" to "Get back to the airport"?

Take a look at the departure end of 27, you'll see the options are limited.
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That's a tad patronizing, Dan. I thought the discussion was about turning back to the runway when the engine quits during initial climb...how did 3000 feet get into the act?

Maybe it's just me, but I want my students to realize that the impossible turn is impossible for most pilots most of the time and that the way to save their skin is to land straight ahead or nearly so. I'm willing to grant that when the plane has attained 1000 feet agl the initial climb phase has been over for quite some time. I'll also allow as how the situation illustrated has few options and is why a pilot should do as much research as possible before rolling into the takeoff position...use runwayfinder.com, ourairports.com, Google Earth or whatever to minimize the surprise factor.

Bob
 
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brcase said:
<snip> As soon as you look away from the airspeed indicator and stop consciously pushing forward on the stick/yoke you will likely start slowing down.

Brian
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OK, let me try to say it differently.

I believe most stall spin accident are caused the the illusion or belief of speed. Flying the approach near the ground, downwind can give a huge impression of (and actual)speed over the ground. This sensation of course has nothing to do with airspeed.

In instrument flying one will want to turn when they get the sensation of turning when they want to go straight, i.e. the "leans" or responding to what you are feeling and not to what is actually happening.

When you get the sensation of speed that you normally should not have you will have a natural tendency to want to correct it, i.e. pulling back on the yoke/stick. You have to combat this the same way you do the "leans" and pay attention to and respond the instruments. If you stop paying attention to the instrument you will start responding to what you see/feel instead and start slowing down.

I think this is what really makes the "impossible turn" so dangerous. We obviously don't practice them at low altitude or obvious reasons, but actually doing the turn at low altitude can look and feel a lot different that doing them at altitude.

Brian
 
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dmccormack said:
It's a worthwhile exercise every pilot should do with each airplane flown.
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But please -- if you've never done one before, get with an instructor who really knows the maneuver for the first attempts. And do those first attempts at a nice safe altitude with a simulated deck at 1500 AGL or so.
 
bobmrg said:
That's a tad patronizing, Dan. I thought the discussion was about turning back to the runway when the engine quits during initial climb...how did 3000 feet get into the act?

Maybe it's just me, but I want my students to realize that the impossible turn is impossible for most pilots most of the time and that the way to save their skin is to land straight ahead or nearly so. I'm willing to grant that when the plane has attained 1000 feet agl the initial climb phase has been over for quite some time. I'll also allow as how the situation illustrated has few options and is why a pilot should do as much research as possible before rolling into the takeoff position...use runwayfinder.com, ourairports.com, Google Earth or whatever to minimize the surprise factor.

Bob
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I apologize for patronizing, but I get miffed by "How dare instructors [whatever aerodynamic heresy]!" replies.

If you ask anyone that's flown with me in the right seat as a CFI, they'll tell you I've asked each one: "What's our turn back altitude?" and "What happens if we lose power before then?"

Most reply "1000 AGL" -- which is fine rote reply, but has no evidence for the pilot or the airplane.

With a few we've climbed to safe altitude and tried it. Every GA single I've been in can at least do a 180 in less than 1000 feet, but then the question is, "Will you make it back to the airport?"

The answer usually ends up "I'll look for something ahead..."

Which isn't always best, either -- fly out of KTEB and let me know where you'll put it down?

This is a theoretical exercise, certainly. But today, in my airplane, at a safe altitude, I tested the altitude loss from a power-to-idle 180.

I'm glad I did because it gave me a healthy respect for the amount of nose-down and bank required to get turned pronto.

Sure, I "knew" it before I tried it, but there's nothing like doing it in the airplane (which is why spin training is so enlightening).

Anyway, I think I've cautioned and warned and laid out concerns consistently through this thread.

But I also think we don't do ourselves any good by declaring certain topics Verboten!

It's like low-level flying -- we can pretend all Good Pilots Will Never Do Such Things.

Or we can show them what's actually do-able, and what might happen if we exceed those limits.

Count me on the "show me" side.
 
Ron Levy said:
But please -- if you've never done one before, get with an instructor who really knows the maneuver for the first attempts. And do those first attempts at a nice safe altitude with a simulated deck at 1500 AGL or so.
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Sure, if you're not comfortable -- by all means get some dual!!!
 
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dmccormack said:
Sure, if you're not comfortable -- by all means get some dual!!!
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I find it quite incomprehensible that someone who's never been trained on this maneuver could be comfortable doing it, but the accident records are full of folks who were comfortable doing stuff they'd never been trained on, so what do I know? :dunno:
 
Dan, I've taught this in umpteen BFRs. Try the same maneuver from 1000 agl and this time actually stop the engine. You are doing this with some reserve thrust, true zero thrust, but not the negative thrust of a windimililng propellor. In fact you need to do it with negative thrust as the propellor will be windmilling, which is a negative thrust position.

After doing it in four or five different types, I have concluded 800 with about a 5 know headwind is about my personal limit. 500-->you're doing something that does NOT simulate a real dead engine with a windmilling propellor.
 
bbchien said:
Dan, I've taught this in umpteen BFRs. Try the same maneuver from 1000 agl and this time actually stop the engine. You are doing this with some reserve thrust, true zero thrust, but not the negative thrust of a windimililng propellor. In fact you need to do it with negative thrust as the propellor will be windmilling, which is a negative thrust position.

After doing it in four or five different types, I have concluded 800 with about a 5 know headwind is about my personal limit. 500-->you're doing something that does NOT simulate a real dead engine with a windmilling propellor.
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Yep -- a long time Aeronca owner who had an actual engine out said the glide difference is noticeable.

I don't think I said 500' AGL is my safe altitude.

I did say I start the turn to crosswind at 500' AGL and then immediate turn to downwind (unless there's other traffic further out). So by 600' AGL or so I'm facing the airport.
 
Ron Levy said:
I find it quite incomprehensible that someone who's never been trained on this maneuver could be comfortable doing it, but the accident records are full of folks who were comfortable doing stuff they'd never been trained on, so what do I know? :dunno:
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Hang on -- what are we talking about? Practicing a Power off 180?

It's part of the Comm PTS, for Pete's sake.
 
dmccormack said:
Not sure I follow... :dunno:
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FWIW, when I've tried this in my taildragger (similar to a Champ) I've found that I can turn around and get re-aligned in as little as 200 ft. What's really surprising is that it appears that the best technique (when solo) is to pull the stick all the way back and hold it there while rolling rapidly (with lots of rudder) into a 45-50 degree bank. The nose falls down on it's own while turning steeply and I actually have to leave the stick back briefly after rolling out to slow to best glide speed. I assume this means the elevator authority is reduced when pulling g's in a steep turn. For comparison from what I recall doing the same maneuver in the Bonanza I used to own did require pushing on the wheel while rolling into the turn and resulted in 600-700 ft of altitude loss. Not sure I'd want to try the Bonanza from as low as 1000 AGL but the Porterfield seems to make it feasible above 500 ft.
 
Palmpilot said:
... If you take the total number of successes for all the sorties shown in that sidebar, and divide it by the total number of attempts, the result is a 62% success rate.
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That 62% includes test rounds where the pilots weren't given any instruction, and some test rounds where the pilots were explicitly given incorrect instruction (they did two rounds where pilots were instructed to perform skidding turns with full rudder deflection).

In the tests where they were given instruction (which was just the bank angle to fly and an instruction to fly an airspeed near stall), they had a 75% success rate at 45 degree bank and a nearly 100% success rate at a 30 degree bank (the one failure was a pilot who was failed for flying a 20 degree bank instead of 30). When I see these numbers, I don't come away thinking "oh, that's clearly an impossible maneuver", instead I come away thinking "I wonder how those numbers would improve with a little training and practice".

I find it curious that we damn a maneuver by testing pilots who have never been trained in it. We don't seem to do that with any other flying maneuver. For everything else, the answer is always "get the training, do the practice, keep your skills sharp"; we instruct, we practice, _then_ we test. But for this we push the results from tests of pilots who aren't trained in the maneuver, and use that as proof that it's too dangerous for anybody to attempt. It just seems like an attempt to control perception instead of to educate.
-harry
 
bbchien said:
Dan, I've taught this in umpteen BFRs. Try the same maneuver from 1000 agl and this time actually stop the engine. You are doing this with some reserve thrust, true zero thrust, but not the negative thrust of a windimililng propellor. In fact you need to do it with negative thrust as the propellor will be windmilling, which is a negative thrust position.

After doing it in four or five different types, I have concluded 800 with about a 5 know headwind is about my personal limit. 500-->you're doing something that does NOT simulate a real dead engine with a windmilling propellor.
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In my airplane, the difference in glide performance with the prop at take-odd fine pitch vs. coarse pitch is striking. With the prop forward, the glide ratio is in the neighborhood of 3 or 4 to 1 and I see a 50% improvement with it pulled back. Is adjusting the prop in my engine out procedure - you bet.
 
bbchien said:
Then I misunderstood you....
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In Post #13 I ran the numbers and concluded that in a no wind situation 500' AGL wasn't enough to make the turn and get back on airport property if engine failed and I was still on runway heading.

IF I'm at 500' AGL and start my crosswind turn -- at about the 90 degree point during that turn I'm past the need for on-the-edge flying, and the airport becomes the "straight ahead" choice.


Hope this clarifies....?
 
Yes, it means you're going to use 800 feet, as I do....I went back to post 13 and read it more carefully....
 
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bbchien said:
Yes, it means you're going to use 800 feet, as I do....
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I do in larger singles.

In my Chief if I wait until I'm 800' before turning crosswind I'm waaaay out there.

If I'm sharing the pattern, I just fit in.

But usually I have the place to myself, and keep it tight.
 
Interesting thread, and I don't have a definitive answer, but I do have some questions.

Shouldn't the "turn back" be based on not stalling instead of getting back to the runway (like any maneuver close to the ground)?

Shouldn't pilots limit their bank in an emergency to whatever they are comfortable with?

Isn't this entire discussion somewhat dependent on the terrain in and around the airport?

Isn't the turn back altitude totally dependent on the airplane and the circumstances?

If I focus on not stalling, and turn at the angle of bank I am comfortable with, then as I roll-out of the turn I take whatever is left. If that is the runway, great. If a taxiway, or the grass, or a road, so be it.

I guess my point is in any maneuver we should be concerned first about flying the airplane safely, then take whatever is available. If flying by myself VFR, I normally make "steep" turns so a 45 degree turn would be more or less normal for me. Every airplane I have flown is airspeed dependent, so that is my focus if the ground is nearby. I have flown from many airports where straight ahead is the worst option. 90 degrees would be pretty easy in many airplanes from 500 feet. But my personal attitude is the airplane belongs to the insurance company when the wheels leave the ground. My primary responsibility is to the occupants until the airplane is parked again.

BTW, the trickier skill to get comfortable with, if it's not part of what you do regularly, might be leveling the airplane out of the turn at 50 ft or so. I would think slipping on short final would be a pretty useful skill as well. Obviously all of this is experience limited.

On the other hand, in helicopters...

If you have an engine failure at night enter autorotation, but leave the landing light off until 500AGL to save the battery. If you don't like what you see when you turn the light on...

turn the light off.:D
 
ebetancourt said:
Interesting thread, and I don't have a definitive answer, but I do have some questions.

Shouldn't the "turn back" be based on not stalling instead of getting back to the runway (like any maneuver close to the ground)?
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What's the first rule of aviating?

Hint: Fly the airplane.


ebetancourt said:
Shouldn't pilots limit their bank in an emergency to whatever they are comfortable with?
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Thus the point of this exercise -- if a pilot only ever does 30 degree banks, do we expect during an emergency suddenly he'll do a 60 degree bank near stall speed?


ebetancourt said:
Isn't this entire discussion somewhat dependent on the terrain in and around the airport?
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Yep. See my link to a satellite image.

ebetancourt said:
Isn't the turn back altitude totally dependent on the airplane and the circumstances?
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No. There's another factor -- pilot proficiency.
 
ebetancourt said:
...Shouldn't the "turn back" be based on not stalling instead of getting back to the runway (like any maneuver close to the ground)?...
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You should certainly factor into your choice the probability of successfully flying the maneuver. If you haven't practiced it, then I suggest you rule it out. If you have practiced it, and found yourself unable to perform it well, then rule it out. But if you have practiced it at altitude, and see reason to believe that you could successfully perform it when needed, then add it to your bag of tricks.

But do note that if you take the maneuver and "adjust it" until it becomes something you're comfortable with, then you might very well have turned it into something useless. For instance, if you decide that you're going to do your turns at 30 degrees bank, and fly at your usual pattern speeds, because you know you're comfortable with those, you've dramatically reduced the set of circumstances under which it will be possible to make it back to the airport grounds, and so the turn becomes pointless.

I don't believe the maneuver needs to be flown to perfection, but you do have to balance ease of accomplishment with performance.
Isn't this entire discussion somewhat dependent on the terrain in and around the airport?
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The whole notion of a turn-back is based on the premise that the best landing opportunity is behind you. If you're out in farm country, the best landing opportunity is likely to be ahead of you. If you're departing from an urban airport surrounded by development, then it might very well be behind you.
-harry
 
mantakos said:
You should certainly factor into your choice the probability of successfully flying the maneuver.
-harry
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My point is that turning back should always be a secondary goal. The first goal is to keep the airplane under control, and the only way you do that is to stay within your limits. Frankly, I think practicing the turn back at altitude is pointless unless you have acquired all of the requisite skills. At a minimum that involves aircraft control close to the ground. There is no way to perform a turn back without turns in two directions (exceptions: major crosswind, multiple runways). One might be very close to the ground depending on how you start and would require rolling smartly from whatever bank to a bank in the other direction. With a strong headwind and good climb angle you might be looking at major slipping to get down with enough runway to have made it worth your effort to turn back. All of which probably adds to the statistics for this maneuver.
 
ebetancourt said:
My point is that turning back should always be a secondary goal. The first goal is to keep the airplane under control, and the only way you do that is to stay within your limits. Frankly, I think practicing the turn back at altitude is pointless unless you have acquired all of the requisite skills. At a minimum that involves aircraft control close to the ground. There is no way to perform a turn back without turns in two directions (exceptions: major crosswind, multiple runways). One might be very close to the ground depending on how you start and would require rolling smartly from whatever bank to a bank in the other direction. With a strong headwind and good climb angle you might be looking at major slipping to get down with enough runway to have made it worth your effort to turn back. All of which probably adds to the statistics for this maneuver.
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I'm confused.

Wouldn't practicing this stuff at a safe altitude be the means to acquire the "requisite skills?"
 
ebetancourt said:
There is no way to perform a turn back without turns in two directions (exceptions: major crosswind, multiple runways). One might be very close to the ground depending on how you start and would require rolling smartly from whatever bank to a bank in the other direction.
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What do you think is going to be required of you when landing straight ahead? Missing trees, houses, cars, telephone poles and wires can very likely require, oh heck, maybe turning in two or more directions close to the ground and some smart rolling and airplane control. This point about being proficient at aircraft control is exactly the point you should be concerned about regardless of where you decide to return to earth. Jeez, you might even have to do a full slip, power off, to get it down in a field without hitting something that would hurt. Those are all reasons for CFIs to teach it and you to practice it so when it hits the fan, you can do some of that real pilot stuff to keep you out of the hospital or worse.
 
PittsDriver said:
In my airplane, the difference in glide performance with the prop at take-odd fine pitch vs. coarse pitch is striking. With the prop forward, the glide ratio is in the neighborhood of 3 or 4 to 1 and I see a 50% improvement with it pulled back. Is adjusting the prop in my engine out procedure - you bet.
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Is that the about the difference between a brick and a streamlined brick?:D
 
dmccormack said:
Hang on -- what are we talking about? Practicing a Power off 180?

It's part of the Comm PTS, for Pete's sake.
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Those aren't done at 5% above stall speed on the practical test, are they?
 
dmccormack said:
Thus the point of this exercise -- if a pilot only ever does 30 degree banks, do we expect during an emergency suddenly he'll do a 60 degree bank near stall speed?
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What advantage is gained by using 60 degrees of bank when 45 degrees gives a smaller altitude loss per degree of turn? According to Figure 8 in the Rogers paper, a 60 degree bank reduces the total number of degrees you have to turn through by maybe two percent or less, which reduces your altitude loss by the same percentage, but according to equation 12 the more steeply tilted lift vector increases your altitude loss by 13%.
 
dmccormack said:
I'm confused.

Wouldn't practicing this stuff at a safe altitude be the means to acquire the "requisite skills?"
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Some of it can be practiced at altitude; I suspect unless a pilot regularly made turns on final with ground reference at somewhat low altitude the actual execution might create an opportunity to "choke." I have no idea how you would practice lining up between the two trees at altitude. A Pitts pilot that regularly performs "arcing" finals would have no problem. A Cessna pilot that always performed "stable" approaches?
 
Palmpilot said:
What advantage is gained by using 60 degrees of bank when 45 degrees gives a smaller altitude loss per degree of turn? According to Figure 8 in the Rogers paper, a 60 degree bank reduces the total number of degrees you have to turn through by maybe two percent or less, which reduces your altitude loss by the same percentage, but according to equation 12 the more steeply tilted lift vector increases your altitude loss by 13%.
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In some airplanes/circumstances altitude loss might be essential. Light, with a reasonable headwind, I can get the Citabria to pattern altitude on 3,200 ft by the end of the runway. If I had an engine failure at that point I would do a 45 degree 360 with a shallow bank "downwind," and land probably midfield. If I had a fire to go with the engine failure, I would use something approaching 90 deg and a dive to put the airplane on the ground ASAP. In the Waco, if I lose the engine at the end of that same runway, I have my choice of maybe 30 degrees either side of whatever I can't see under the nose.

Ernie
 
ebetancourt said:
Some of it can be practiced at altitude; I suspect unless a pilot regularly made turns on final with ground reference at somewhat low altitude the actual execution might create an opportunity to "choke." I have no idea how you would practice lining up between the two trees at altitude. A Pitts pilot that regularly performs "arcing" finals would have no problem. A Cessna pilot that always performed "stable" approaches?
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I slip between a V in the line of trees on the approach to 27 just about every time I land.
 
EdFred said:
If you are REAL good, you go nose up, put in 1/2 a turn of a spin , nose down, then flare...Wheeeeeeeeeeeeeeeeeeeeeee!

I've only done this successfully....never.
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How many times were you unsuccessful?
 
dmccormack said:
Who's levying that requirement?
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That's the airspeed recommended by Prof. Rogers. For a pilot who plans on using his method, I can see how Ron's recommendation to have CFI on board when trying it for the first time would make sense.

One can, of course, use a higher airspeed, at the price of losing more altitude than Rogers predicts.
 
ebetancourt said:
In some airplanes/circumstances altitude loss might be essential. Light, with a reasonable headwind, I can get the Citabria to pattern altitude on 3,200 ft by the end of the runway. If I had an engine failure at that point I would do a 45 degree 360 with a shallow bank "downwind," and land probably midfield. If I had a fire to go with the engine failure, I would use something approaching 90 deg and a dive to put the airplane on the ground ASAP. In the Waco, if I lose the engine at the end of that same runway, I have my choice of maybe 30 degrees either side of whatever I can't see under the nose.

Ernie
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In most circumstances, having excess altitude when the engine quits is a GOOD kind of problem to have!
 
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