Impossible Turn Testing

[Ed Cesnalis]

In a 45 degree bank back to the runway one problem is you can't see (assuming a high wing CT) and if you visualize incorrectly you will end up somewhere other than where you need to be.

 

Practice the impossible turn for the purpose of identifying your ground track when you are banked and cannot see where you are going.

 

Look at the video below and at 40 seconds in I'm turning base to final with a steep turn and cannot see the runway at all but due to the old runway still being there I know its the correct track.  I use the visual clue to roll out of my turn on the extended runway center line. (yes its a sloppy turn)  If you know the ground track from prior practice you can use steep banks and still find your way.

 

[Ed Cesnalis]

If you can't deal with that situation, you need to stop flying.

 

I think it is a tongue in cheek response to being told you will die if you try it at 500'.  Its not only doable but we have learned in a CT your problem may very well be that you are too high.

 

Ask Sandpiper, an experienced CFI, when he tried the IT he had to use a max performance slip to get down.

[FlyingMonkey]

Once again, I dare anyone to try the turn with engine idle at 500 feet agl after clearing the end of the runway.  It will be the last turn you ever try to make.  The chances of a cross control deadmans stall/spin, or the loss of too much altitude in a steep turn that close to the ground is a great way to end your flying days.

Three days ago a friend of mine went up in calm conditions, flying his Avid Flyer. He climbed to 400ft, set power to idle, and did an immediate turn back and landed on the same runway he departed on without any problems.

 

How do you account for this?

[coppercity]

As mentioned, knowing your aircraft capabilities and systems is key to sound aeronautical decision making.  One thing that is hard to get into peoples head is that the lives inside the aircraft are far more important than the aircraft itself.  Sometimes to much emphasis is placed on trying to save the aircraft vs making the decision to land off airfield or in the parachute.  Many times the later can provide a good margin of safety to the occupants but require a replacement aircraft. Ultimately every situation is different, aircraft capabilities are different, environmental conditions are different, and pilot skills are varied but I hope I can give my students the ability to make the best decision possible for saving themselves and passengers without thought of trying to save a replaceable piece of hardware.

[Jim Meade]

I very much agree with the imperative to know yourself, your airplane and the conditions.

 

For CT - without being in my plane to check, in a 45° bank on the turnback, what can one see from the overhead skylight? I often fly carrier approaches and nearly always fly from the right seat, so I'm used to not seeing what others would like to see. When flying at a lesser bank angle, I usually simply adjust my bank angle to give me a momentary glimpse, but I will admit that in a performance turnback that tactic may not be available.

 

An an aside, if one finds one's self in this position one hopes one has the presence of mind to check for other traffic, although one would be surprised if someone was landing from the opposite direction on the runway one just took off from. Still, it's not unheard of if there is a direct crosswind and the crop duster or charter jockey is simply making a direct in from wherever he is.

[Ed Cesnalis]

in a 45° bank on the turnback, what can one see from the overhead skylight?

 

Turning left or right?  With high terrain I turn both.  Right seat or left?

 

I don't think its ever in the right place, but I'll have another look.

[FastEddieB]

Maybe I am unfair to Ed, but what I hear him say is never turn back.

Gee, I thought I went out of my way NOT to say that.

[FlyingMonkey]

Gee, I thought I went out of my way NOT to say that.

 

Agreed, I asked you specifically in post #39 and you said that is not your position.

[Jim]

Once again, I dare anyone to try the turn with engine idle at 500 feet agl after clearing the end of the runway.  It will be the last turn you ever try to make.  The chances of a cross control deadmans stall/spin, or the loss of too much altitude in a steep turn that close to the ground is a great way to end your flying days.

Read post #12 on page 1.  I did it.  I did it three times and didn't break the airplane.  I'm not sure why you say the things you say, but it is a disservice to the people trying to learn something.

 

A little bit of math.  Accelerated stall speed is the square root of the load factor times normal stall speed.  Call normal stall speed 38 knots.  That would make the accelerated stall speed at 45 degree bank 46 knots.  At 60 knots, I feel you are a long way from there.  Maybe outside your comfort zone at 500 feet, but not mine when the options in front of me are less than optimal or when I want to train for a bad day.

 

If you fly a CT, go up to a comfortable altitude and do some 180 degree coordinated turns at 45 degree bank and 60 knots.  Then cut the throttle to idle, pitch for a 60 knot glide and do one.  You won't fall out of the sky.  Not there or at 500 feet agl.

[Tom Baker]

All of this makes good reading, but the bottom line is whether you can or can't depends a on a whole bunch of factors. I have flown airplanes that by the time you get to 500 feet there would be no way you could make it back to the runway. I have flown others that when you reach 500 feet if you try a 180 you will run out of runway trying to land, because you are not far enough down the runway. I also know someone who tried to turn back and didn't make it. They did survive, but had a broken back.

[Jim]

You did it with total engine out or at idle no fudging....I don't believe it. 

 

By the way, we are not doing party talk and sharing campfire stories here, we are talking about getting killed...giving newbie pilots the impression the impossible turn is possible is not just irresponsible, it's malicious.

 

Believe what you want.  I think I've established my reputation here for truthfulness and accurate, factual information.

 

I don't believe any pilot should perform a maneuver in an emergency situation that they are not familiar with.  And I do believe a "newbie pilot"  should train with an instructor on any maneuver outside their comfort zone.  Finally, I think everyone should become familiar with all the characteristics and potential that their aircraft can provide.

[IrishAl]

Hi guys.

 

Jim Meade’s recommended articles are very instructive, and they really address my need to understand where the parameters are in a turn back to the runway.

 

However, the conclusions surprise me, and I’d like to share them here for scrutiny and possible correction.

 

The most surprising thing in the first paper (http://jeremy.zawodn...ng/turnback.pdf) is that ‘best gliding turn’ speed is shown to be significantly lower than ‘best glide’ speed.  I had assumed that V L/Dmax would remain pretty much the same whether in level flight or in a turn.  But the paper concludes otherwise, stating that:

 

the optimum speed for minimum loss of altitude in a gliding turn to a new heading occurs for CLmax, i.e., at the stall velocity.

 

As a result, this paper significantly alters my understanding of what I should do in an engine out scenario.

 

To put it simply, here’s how:

 

I already know that in order to get the best glide range out of my aeroplane I should adopt best glide speed, 58kts in my case for a C42.

 

But in order to make the most efficient turns, I need to lower the speed significantly, as the most efficient turn speed is stall speed.  (And, of course, add on a margin for safety.)  

 

Here’s how it calculates out for the recommended best bank angle of 45 degrees: 

 

Stall speed at 45 deg is Vs x 1.13 (1.13 being the sq root of the load, which is 1.41g at 45 deg bank). 

 

Then add the 5% safety margin, as recommended in the paper.

 

So, for the plane I fly, this equates to 41kts x 1.13 x 1.05  = 48.6 kts. 

 

Personally I think 1.05 is too small a margin so let’s give it 15%, or 53kts.

 

Thus, if my engine dies when I’m fully laden, and I elect to turn back, my best course of action is to enter a 45 deg bank, drop the nose sufficiently to maintain 53kts and when the required heading has been achieved, level the wings and trim for 58kts.

 

When I did my ‘experiment’ last week, as described earlier, I kept my glide speed well over 60kts during the turn as I didn’t know where the edge was.  Knowing now that I can make this turn safely at 53 kts will significantly reduce the height lost in making the turn.

 

Is my understanding of this sound, and are my conclusions correct?

 

(Jim’s précis of the second paper by Barry Schiff (post 47) shows that Schiff requires best glide speed in the turn rather than stall speed.  This flatly contradicts the first paper and makes me a little more uncertain of my conclusions.)

[Ed Cesnalis]

What about turning back from a distance?  What does it take to achieve a climb gradient that is steeper than your glide?  Does Vy get you there? Vx?

[FastEddieB]

I think the Darren article is fraught with the very type of misinformation we have seen in our discussion.

That may be very true, but I think it's a misnomer to call it "the Darren article", as if he were responsible for its contents. CharlieTango also referred to it as if it were Darren's work.

 

If you look at the bottom, he credits the article to an FAA publication.

 

(END OF DOCUMENT FAA-P-8740-44 AFO-800-1283)*

 

And CFI's are in a more awkward position than the average pilot. While any CFI may wish to teach techniques above and beyond FAA minimums, he or she must beware the impression left when they say, "I know what the FAA says, but we'll do it my way". We also have to teach "by the book" to get students through checkrides.

 

I never got sued by a student or their survivors, but if a pilot were killed attempting "The Impossible Turn", a lawsuit might bring up teaching techniques that were contrary to FAA recommendations and publications. It could get very hot on the witness stand if asked, "And why, exactly, did you think you knew better than the FAA?"

 

But, again, do what you want. It's NOT impossible. If you train repeatedly for it and keep proficient in it, it can become "just another maneuver". But I'll continue to focus more on landing spots in front of me rather than behind me - my individual skill set should permit me to land my Sky Arrow in the least bad area ahead at 40k or less groundspeed and survive. I think the way I've trained usually makes that a better option. For me.

 

YMMV!

 

*Edited to add:

I Googled the publication number to find the primary source. Interestingly, this came up:

 

http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20001212X21165&ntsbno=CHI00FA165&akey=1

 

It's an accident report where that document is referenced, and quoted. The quote that the investigators thought was relevant?

 

FAA publication FAA-P-8740-44, entitled "Impossible Turn", states that, "Turning back is the worst possible action when the powerplant fails during climbout in a single [single engine airplane]." A copy of FAA-P-8740-44 is attached to this factual report.

 

Please check out the report. The pilot was a Commercial Pilot with 2,700 hours, and the Citabria is capable of aerobatic maneuvers. The failure occurred lower than we've been discussing here. Maybe this pilot had trained for "The Impossible Turn". Maybe not. But in the heat of battle it did not work. We can only speculate the outcome if he had continued straight. But if the pilot were miraculously given a "do over", I bet he'd try that instead.

[opticsguy]

I've done this at idle multiple times starting at 500' AGL.  It was a fairly windy day and had enough height to line up on the runway but I was already halfway down the 5500' runway (I pulled power just past the departure end).  I did this from 600' with an instructor during a BFR.  I use 0 flaps and 68-72kt, 45 degree turn.

 

If I was at 400' I'd still try it since the chance is high of getting inside the fence and onto some mowed grass.  If you have to go off the end into a chain-link fence, that's probably the best thing to hit for you and maybe you plane.

[Ed Cesnalis]

I"m not terribly impressed with this AOPA video.  They give you the impression that the 'impossible turn' is a simple 180 and they demonstrate a 180 losing as little as 300'

 

One of the conclusions is if there isn't a field strait ahead or slightly to the left or right the pilot might try the impossible turn.  

 

There are many options in between, one of mine would be a crosswind turn and land on the road oriented 90 degrees to the runway.

 

http://www.aopa.org/AOPA-Live.aspx?watch=lyOHVoMjr2oVEH1Ipz6TLpnTSBQ8LWRR

[Ed Cesnalis]

Much better video.  I didn't have a turnback number for my 172, I have been using 600' for my CT.

 

 

[Ed Cesnalis]

This video demonstrates that a light sport could in fact work with less altitude.  It also deals with delaying the turn so you are not too high and overshoot your downwind landing.

 

[Ed Cesnalis]

 

looks easy

[Tom Baker]

Just a quick note about the Cub video. The Cub is different from our airplanes. While the CT's have residual thrust with the engine at idle compared to a stopped propeller, the Cub has more drag. I have quite a bit of time in Cubs, Taylorcrafts, and Champs. They will glide farther with the engine and propeller stopped than they will at idle. That slowly rotating propeller creates lots of drag.

I say this, because there is a forum member who will chime in saying if the engine was stopped he couldn't have made it.

[Ed Cesnalis]

Just a quick note about the Cub video. The Cub is different from our airplanes. While the CT's have residual thrust with the engine at idle compared to a stopped propeller, the Cub has more drag. I have quite a bit of time in Cubs, Taylorcrafts, and Champs. They will glide farther with the engine and propeller stopped than they will at idle. That slowly rotating propeller creates lots of drag.

I say this, because there is a forum member who will chime in saying if the engine was stopped he couldn't have made it.

 

I've looked at a few videos now and I think the criticism about not using a pause before reacting or benefiting from idle power is missing the point.

 

If you go as far as doing simulations at real altitudes (below 700' for a CT) then  you are getting some valuable training.  'Practicing bleeding' (pausing) isn't the part that's important in these drills.  I don't think any of us are going to use our best practice at idle for a real number.

 

I think the value of the cub demo is that it shows that all aircraft don't need 1,000' or more. 

[FlyingMonkey]

...giving newbie pilots the impression the impossible turn is possible is irresponsible IMHO.

You are a newbie pilot, and can make up you own mind. I am newbie pilot and can also make up my own mind. Who are these starry-eyed innocents who we dare not expose to any opinion differing from that in FAA documents and publications?

[WmInce]

. . . "giving newbie pilots the impression the impossible turn is possible is irresponsible IMHO." . . . 

 

Why don't you sit on your hands and watch for a while . . . you may learn something from these well experienced guys that just may save your bacon some day.

[Roger Lee]

I can do 500' AGL without much effort. I take off at 15 flaps and 60 Knot climb. If the engine goes it is nose down and turn without any hesitation. With those settings I don't have to adjust or make any corrections for landing, just fly the plane. I'm well practiced from the 2 stroke Ultralight days. Hesitation and panic are a combination for disaster.

If the engine coughs or sputters I make the immediate turn and plan to land not look to fix issues as you loose additional altitude. Runways, taxiways or side roads become an immediate landing spot.

[Ed Cesnalis]