Practicing the "Impossible Turn"

MarcoDA40

MarcoDA40

Pre-takeoff checklist
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Apr 14, 2015
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Marco
Hello POA,

A few months ago I started a paid apprenticeship at a local flying club for my A&P.
Its a fleet of of 14 aircraft. Mooneys, 152s, 172s and Piper Warriors.
I've been checked out in all of the planes except the Mooney, but I'm reaching the hour requirement so I'll do that soon.
Anyways, the nature of my job includes test flying the planes after we've done repairs.. flying them when they get squawked (just yesterday we had a high oil temp squawk on a piper, had to fly it around a bit and ended up changing the thermostatic bypass valve).
My boss, A&P IA and fellow pilot asked my instructor to nail emergency procedures down.
We went up in a 172 yesterday for 1.7hrs and just did emergency procedures the whole time.
Towards the end of the flight we went up to 3k and practiced departure engine out at altitude.. we climbed to 3500ft, pulled power and made a 180. 70kt, 45 degree bank and NO STALL HORN. We did that 5 times and each time I was able to complete the turn with 120-150ft to spare.
We then went down for a full stop, taxied back and he said to just do a normal takeoff and we will do a few soft field landings and call it a day(lies lol). At exactly 500ft AGL, he pulled the power and said "your time to shine". I leveled the nose and immediately began a 45* bank right turn into the wind (runway 21, wind was 230@9) kept it between 67kt-75kt. Again, I was able to complete the turn with about 120-150ft to spare. The hardest part of this whole procedure was landing with a 8ish knot tail wind. Greased the landing but I took up way more runway than I had expected. Left flaps up due to the tailwind.
There was absolutely zero traffic in the pattern or around the area.

This was probably the coolest thing I have done training wise. I wish we could have done it more than once but I understand this isnt something you want to be doing too often (at least from my perspective). Power off 180s were a freaking breeze after that. Not that they're hard but they became that much easier.

Peace
 
Not trying to burst your bubble, but consider a few things going forward. You already know that if it’s not executed exactly right, it can lead to the classic stall/spin.

Your proficiency in doing this (the after takeoff training event) will diminish unless you do it all the time. And, as you stated, you don’t want to do it all the time. So, there’s that. Later, when you fly for pleasure and not for training purposes, the surprise factor when losing an engine at 500 feet will be different than what you experience now and will impact your performance. What if it fails at 400 feet or 300 feet? Will you immediately start this maneuver? Discipline on when this is attempted will be paramount.

There are a few videos on YouTube of successful and unsuccessful attempts. I recall another one of an engine failure and forced landing straight ahead. You can hear the pilots breathing rate and anxiety level go through the roof.

Flaps up for tailwind?
 
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MarcoDA40 said:
Left flaps up due to the tailwind.
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Along with asicer, I was wondering about this. How exactly would that help, or what did you see it avoiding?

I’ve never practiced nor taught “impossible turns”, except maybe a few times at altitude. In real life, an unexpected power failure will result in about a 3-second delay, and over that 3 seconds in a nose up attitude airspeed will decay precipitously, to very close to the stall speed. It’s reflexively honking in a large bank angle at that point that can be fatal. And speaking of reflexes, in spite of knowing better many pilots will hurry the turn back to the runway with rudder, and the stage is set for a spin. But this is an old debate, that I don’t see either side winning, so there’s that.
 
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I practice impossible turns in every aircraft I fly, because no two plane fly exactly alike, even within types.
I practice them, upwind and down wind at all the airports I regularly fly into, because the sight picture and the airports are all different.
 
MauleSkinner said:
It’s the logic of making a change in the stress of the event rather than following the plan.
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Exactly. This is where you have a plan and execute. The plan may be full flaps (or half, or no flaps), but whatever produced the best results in simulations is what you always want to use. And headwind/tailwind has nothing to do with it.
 
Regarding the flaps/no-flaps question, depending on a number of factors you may or may not be within gliding distance of the runway after the turn is completed. I would not do anything to steepen the glide angle unless I saw that the threshold was getting lower in the windscreen once I was on final.
 
When contemplating doing this with a student, the first thing that comes to my mind is "How will I explain my decision to practice this inherently dangerous procedure to an administrative law judge at the inevitable hearing?" Then we get some altitude and practice with a safety margin.

Bob Gardner
 
Palmpilot said:
Regarding the flaps/no-flaps question, depending on a number of factors you may or may not be within gliding distance of the runway after the turn is completed. I would not do anything to steepen the glide angle unless I saw that the threshold was getting lower in the windscreen once I was on final.
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Of course.

But wouldn't a tailwind require one to increase, rather than decrease, rate of descent, all things being equal? Requiring more flaps, rather than none?

Reading "Left flaps up due to the tailwind" leads me to wonder if the reason has something to do with visualizing the wind "pushing" the plane. But I'll readily admit the my "Stick and Rudder Moment" radar is sometimes overly sensitive!
 
FastEddieB said:
...But wouldn't a tailwind require one to increase, rather than decrease, rate of descent, all things being equal? Requiring more flaps, rather than none?...
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If there's more than enough tailwind to get you to the runway, I agree. I was just explaining how I would make the decision.
 
The flaps should be used as needed to reach the touchdown zone. That zone could be shorter or longer depending on the length of the runway. If you landed long with the flaps up they should have been used. Keep in mind there is residual thrust with the motor at idle so if it were a real event your glide ratio will be less.
 
FastEddieB said:
Along with asicer, I was wondering about this. How exactly would that help, or what did you see it avoiding?

I’ve never practiced nor taught “impossible turns”, except maybe a few times at altitude. In real life, an unexpected power failure will result in about a 3-second delay, and over that 3 seconds in a nose up attitude airspeed will decay precipitously, to very close to the stall speed. It’s reflexively honking in a large bank angle at that point that can be fatal. And speaking of reflexes, in spite of knowing better many pilots will hurry the turn back to the runway with rudder, and the stage is set for a spin. But this is an old debate, that I don’t see either side winning, so there’s that.
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While I agree with the general message, I have never experienced this airspeed decaying close to stall upon losing an engine. It is nearly impossible to stall an airplane with power off even if your trim is all the way up. The stall is cause by the pilot pulling on the yoke trying to maintain the same pitch attitude that he had with power. What I try to teach is to trim the airplane for best glide speed and then not mess with the yoke, except for banks.
 
sarangan said:
While I agree with the general message, I have never experienced this airspeed decaying close to stall upon losing an engine. It is nearly impossible to stall an airplane with power off even if your trim is all the way up. The stall is cause by the pilot pulling on the yoke trying to maintain the same pitch attitude that he had with power. What I try to teach is to trim the airplane for best glide speed and then not mess with the yoke, except for banks.
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The problem comes when it happens for real, and looking out the windshield is scary enough without the nose coming down.

fortunately when my low altitude failure happened, I had other things to think about while training and reflexes landed the airplane.
 
sarangan said:
It is nearly impossible to stall an airplane with power off even if your trim is all the way up.
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I realize context is everything, but as a standalone sentence that’s just SO wrong. And pilots do it all the time, both while practicing and in the heat of battle.
 
FastEddieB said:
I realize context is everything, but as a standalone sentence that’s just SO wrong. And pilots do it all the time, both while practicing and in the heat of battle.
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My point was that pilots should resist the temptation to pull back when power is lost. With power off, you can't stall a typical airplane without actively pulling back on the controls.
 
Brian Schiff has a very good seminar on this that you can access through the NAFI mentor live site.


https://www.nafinet.org/index.php?option=com_jevents

In brief, you need to measure altitude loss through 360 degrees, not 180, and add a fudge factor for doing this safely in real life.

Most people find that 750’ AGL is about right for a 172. Below that, land ahead.
 
PeterNSteinmetz said:
Brian Schiff has a very good seminar on this that you can access through the NAFI mentor live site.


https://www.nafinet.org/index.php?option=com_jevents

In brief, you need to measure altitude loss through 360 degrees, not 180, and add a fudge factor for doing this safely in real life.

Most people find that 750’ AGL is about right for a 172. Below that, land ahead.
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It's not clear how to access that seminar on that Web page.
 
I believe nearly every instructor I’ve had (mostly old and not bold) have allowed me to fly at least one of these, unless our training was good work. Once. The hood work ones have made me do the nearly identical Circle To Land published instrument procedures.

You work it up at altitude, and as a final building block do it once lower so the experience bucket actually sees the relative speed of the ground and the mild pucker factor of the sight picture.

Before even doing it, just fly a low pattern somewhere. Fly ten if you like. Has to be done below 1000 AGL all the time to train and demo many instrument Circle to Land published procedures. Sometimes that may even be best done as a close in nearly power off 180.

Glider pilots do it regularly also in training. Both from the simulated rope break position and from simply screwing up their estimate of getting back to the pattern at the correct altitude.

In general, the maneuver itself isn’t really all that uncommon in flight training nor hard to build up to.

The killer is not knowing to push the damn nose down, immediately, and that can be taught and repeated again and again at altitude until it’s the natural response.

The reason it gets labeled “impossible” is because the building blocks leading up to it get skipped or omitted from too many people’s training.

Whether you or the instructor want to see one at low level after building those blocks is a slightly higher risk, and not much higher than any of the above things you could and should have already done.

Haven’t seen anybody practicing for the Commercial not get low at least once when learning power off 180s... the gliders fare better, considering their performance margin... but you still see students wait or hesitate and end up lower than they needed to be over the threshold.

For the powered types, just another moment to practice excellence and call the go around. LOL. If it doesn’t go, which can happen for all go arounds... well, fly it through the crash and avoid large objects that cause sudden decelerations. Those hurt.

As does landing faster and hitting them because you didn’t use flaps once the runway was assured. You’ll whack the thing and experience forces squared by the excess speed. Physics. Yay.

If you’ve got no experience in the building blocks experience bucket that leads to a low level Circle To Land, the “impossible” turn probably really is... impossible. Or at least the wrong place to start.
 
Jeff767 said:
... Keep in mind there is residual thrust with the motor at idle so if it were a real event your glide ratio will be less.
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I thought a stopped propeller develops less drag than an idle or windmilling one. Obviously, feathering the prop is best for glide.
 
Cogito said:
I thought a stopped propeller develops less drag than an idle or windmilling one.
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I think that’s correct. The problem is most propellers don’t stop when the engine loses power. Granted, a seized engine or a catastrophic internal failure might, but I think those are exceptions.
 
Cogito said:
I thought a stopped propeller develops less drag than an idle or windmilling one. Obviously, feathering the prop is best for glide.
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I was very surprised to observe, as I did a power off landing simulating an engine out scenario, when I pulled the prop all the way back, the aircraft actually accelerated; you could FEEL it.
I now will always do this if I ever have to do it for real.
 
guzziguy said:
I was very surprised to observe, as I did a power off landing simulating an engine out scenario, when I pulled the prop all the way back, the aircraft actually accelerated; you could FEEL it.
I now will always do this if I ever have to do it for real.
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Are you saying the airplane had less drag with the prop at flat pitch? You'd do well to confirm that with glide tests at altitude. High pitch is the way to go with a windmilling engine. Feathered is best, stopped is second best.
 
I'm an acro pilot, so have been toying with the notion that there might be some kind of maneuver to accomplish a power-off reversal with less altitude loss than a 45 banked turn. Maybe a 90 degree roll to knife edge, let the nose fall through to vertical while continuing to roll to runway heading, then recover from the dive? Sounds idiotic and probably is, but one of these days I'm gonna go up high and see how much vertical it costs me.

Another even crazier notion would be a deliberate half-turn spin. That sounds downright insane, but a typical taildragger with a large rudder can be spun and recovered with good precision. IAC contest standards for spin recovery are within 5 degrees of desired heading.
 
FastEddieB said:
I think that’s correct. The problem is most propellers don’t stop when the engine loses power. Granted, a seized engine or a catastrophic internal failure might, but I think those are exceptions.
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Hmmm, I can personally attest to the fact that a Rotax 912is won't windmill when the engine quits (a test for an aircraft manufacturer) unless you put the plane in a steep dive and then only briefly. Doesn't your Sky Arrow have a Rotax, Eddie? If you have a ULS it has lower compression, but still has the gearbox, will the prop windmill if you shut off your engine? If you haven't tried it, I'm absolutely not suggesting you turn off your engine in flight.~
 
kyleb said:
Are you saying the airplane had less drag with the prop at flat pitch? You'd do well to confirm that with glide tests at altitude. High pitch is the way to go with a windmilling engine. Feathered is best, stopped is second best.
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The flattest pitch is when you push the prop control all the way in. That's why it gives you the highest RPM. He's pulling the prop control all the way out, which gives you the steepest pitch. That's as close to feathered as you can get on a single.
 
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Palmpilot said:
The flattest pitch is when you push the prop control all the way in. That why it gives you the highest RPM. He's pulling the prop control all the way out, which gives you the steepest pitch. That's as close to feathered as you can get on a single.
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You're right. Brain lock on my part.
 
BTW, when you get to training in the Mooney, lot of instructors aren’t Mooney savvy, if they tell you to climb to 3500’ agl to practice slow flight/stalls, you might want to ask for someone with more experience.
Mooney recommendation is 6000’ or higher (it’s in the POH), they can lose 2000’ in one spin rotation. My instructor took me to 8500’, and he was Thunderbird pilot.
 
I can tell you that even when all hell broke loose (things coming through the case and whatever) in my engine, the prop continued to turn.
 
write-stuff said:
What you practiced was a "possible turn". Impossible turns, by definition are impossible. Part of your training should have been to determine whether it is impossible, improbable, or impossible.
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It must annoy you no end when The Man Of La Mancha sings "To Dream The Impossible Dream..." :p
 
FastEddieB said:
Along with asicer, I was wondering about this. How exactly would that help, or what did you see it avoiding?

I’ve never practiced nor taught “impossible turns”, except maybe a few times at altitude. In real life, an unexpected power failure will result in about a 3-second delay, and over that 3 seconds in a nose up attitude airspeed will decay precipitously, to very close to the stall speed. It’s reflexively honking in a large bank angle at that point that can be fatal. And speaking of reflexes, in spite of knowing better many pilots will hurry the turn back to the runway with rudder, and the stage is set for a spin. But this is an old debate, that I don’t see either side winning, so there’s that.
Click to expand...
If you’re trimmed for Vy which is usually close to best glide then even if power quits you’d have to fight the trim to get it slower no?
 
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