The Unforgiving (née Impossible) Turn.

[Garfly]

https://airfactsjournal.com/2020/09/stop-calling-it-the-impossible-turn/?trk_msg=90VGAC9HIQ84R9AP8UUI9VCVR8&trk_contact=TP0NO766QS9G20UOM7VT2QLI2S&trk_sid=2ETHUSOKBNJKR10J4BA71266JO&utm_source=listrak&utm_medium=Email&utm_term=READ+MORE&utm_campaign=F20093A&utm_content=Stop+Calling+It+The+Impossible+Turn

[walrus]

Agree with the article, have had it demonstrated and practiced it with an instructor. It is a type specific thing. Unless you have trained for it and practiced it in your own aircraft, DON'T TRY IT.

[RFguy]

Well I have a story to tell about this. I have had it demonstrated to me it is possible.

 

Reading that article as a fresh student being challenged multiple times daily with engine fail drills in circuits, my feeling is that that article is very conservative and really represents flying 101 - practice your glide approaches regularly from all different situations.....

 

Now, as for "the impossible turn" :

 

While it has been drummed well and truly into me, do not turn back, since I have had more EFATO drills thrown at me than i can remember, I am aware that the math says the energy was available to do it with a bit of height. And so my instructor did an EFATO on me, and showed me that it is possible,

 

My instructor of 50 years flying experience at I think about 500 ft AGL (I think?) in still air nil wind, on the upwind climb, simulated engine failure, then put it into a steep banked (~45-60 deg) descending turn , and put it back down on the strip (downwind) ... It was an aggressive but smooth maneuver, Not once in the maneuver did the airspeed drop below about 70 kts (flaps up, Vstall=45 kts@MW).

Then he told me- while it is possible with much experience of flying and the plane, do not do this ! always choose a less hazardous option , for example if there are flat fields of Canola available....than this one.

Obviously there is a minimum amount of altitude required to execute this maneuver. That would be able to be calculated fairly easily for a particular plane and wind* .'

 

I don't think it would be possible at less than about 350 feet judging by the altitude loss, * or with much headwind (which turns into a tailwind half way round your turn back to the strip 'the wrong way')

 

Glen.

[skippydiesel]

Agree with the article, have had it demonstrated and practiced it with an instructor. It is a type specific thing. Unless you have trained for it and practiced it in your own aircraft, DON'T TRY IT.

 

I agree - further: the type of aircraft, its stall & glide speeds, are very much a factor in this manoeuvre. Your avenge GA "spam can" is unlikely to make such a turn/landing safely.

[M61A1]

This has been posted before with much discussion about various things, but it comes down to the words at the start....Know your airplane and know your own limits.

 

 

[old man emu]

I found this bit very interesting: the first step was to turn left, count a few seconds, then turn back around 270 degrees to the right in order to line up on final. It sounds very much like an informal application of the formal Tear-drop turn for IFR flight:

 

Teardrop Procedure -

 

When a teardrop procedure turn is depicted and a course reversal is required, unless otherwise authorized by ATC, this type of procedure must be executed. The teardrop procedure consists of a departure from an IAF on the published outbound course followed by a turn toward and intercepting the inbound course at or prior to the intermediate fix or point. Its purpose is to permit an aircraft to reverse direction and lose considerable altitude within reasonably limited airspace. Where no fix is available to mark the beginning of the intermediate segment, it shall be assumed to commence at a point 10 NM prior to the FAF.

 

At B, enter a standard-rate turn for 30 degree change of heading. Time one minute from B to C. At C, enter standard-rate turn for a 210 degree change of heading, rolling-out on the reciprocal of the original entry heading. As usual, intercept the inbound course based on the CDI or ADF.

 

This sort of turn is also used by crop dusters (Go to 2:50 and watch after that)

[M61A1]

Your avenge GA "spam can" is unlikely to make such a turn/landing safely.

 

Below is cut and paste from the comments to the article in the OP's link. Note that he's driving a Mooney.

 

 

Bank angle and TAS are the drivers re how long it takes to complete a 180. The formula for rate of turn is 1,091 x (tangent of the bank angle)/TAS. Because the tangent goes up with angle of bank any increase in bank will increase rate of turn and any increase in speed will reduce it. And since the distance between a dead-stick airplane and the ground can be measured in precious seconds, an expeditious rate of turn is desirable. To point out the obvious, more bank and lower TAS are what you want (with an eye on best glide speed and stalling speed as g’s increase). To illustrate: a 180° turn at 30° of bank at 85 KTAS takes 24 seconds to complete; a 180 at 45° takes 14 seconds; and a 180 at 60° can be completed in only 8.1 seconds. Double the bank from 30 to 60 and cut the time needed to head back to the field from 24 to 8 seconds. The steeper bank has the added advantage that the offset from the runway is less on rollout.

 

Yes, we are all aware that steep-banked turns near the ground invite a stall. A 2 g tug on the yoke will stall my 20E at 90 KIAS; coincidentally, 2 gs are required to hold a plane in a stable 60° bank turn. Not much room for error when you slip below Vy and crank it over to 60° of bank.

 

Practice

Several iterations (at altitude) in a Mooney 20E yielded average altitude losses in a 180° turn of:

360′ lost at 30° bank,

270′ lost at 45° bank, and

200′ lost at 60° bank.

[Garfly]

This has been posted before

 

 

As far as I know, this is a new AFJ blog by John Zimmerman. The subject itself, though, for sure, is old. As Zimmerman himself puts it: "some topics seem to come in and out of fashion like bell bottoms." When we're on about this we give AoA and BRS a rest. ;-)

[Student Pilot]

How goes it Gazza?

[M61A1]

As far as I know, this is a new AFJ blog by John Zimmerman. The subject itself, though, for sure, is old. As Zimmerman himself puts it: "some topics seem to come in and out of fashion like bell bottoms." When we're on about this we give AoA and BRS a rest. ;-)

To clarify....The Carbon Cub link has been posted before...I posted it. But yes, "The impossible turn" has been done before, even by the Late Maj Millard who was taken by it. Just not this article which seems quite sensible, but no doubt will be ridiculed by some as "irresponsible".

[turboplanner]

My instructor of 50 years flying experience at I think about 500 ft AGL (I think?) in still air nil wind, on the upwind climb, simulated engine failure, then put it into a steep banked (~45-60 deg) descending turn , and put it back down on the strip (downwind) ... It was an aggressive but smooth maneuver, Not once in the maneuver did the airspeed drop below about 70 kts (flaps up, Vstall=45 kts@MW).

Then he told me- while it is possible with much experience of flying and the plane, do not do this ! always choose a less hazardous option , for example if there are flat fields of Canola available....than this one.

What would have been the result if, instead of starting to react when he did, he sat there and counted six seconds and then tried to complete it?

The difficulty with EFATO practice, and forced landings as well is that we know we are going to do one. Usually the Instructor tells us he is going to give us a few today, and we are primed up and ready with a 50/100 sec reaction. If we are going out to practice ourselves, recation time might even be 25/100 sec. Even if we decide to set a random alarm to give ourselves a surprise we are still ready.

 

However, when the engine starts to die on a perfectly normal operation, unless you've built a subconscious process, the mind starts to analyse what is happening and you go from hundredths of a second to multiple seconds. On one occasion when the front rod end snapped on my race car I watched the wheel try to pass the car as I accelerated, and go backwards when I lifted my foot, and it was maybe 10 seconds or more before I woke up that I could be thrown into the air, and slowly bled off speed.

 

It's that time-delay factor that leads to the policy of landing straight ahead with no more than 30 degree deviation no matter what you're going to hit. That's where the optium percentages are.

 

We've had several threads on this subject over the years where someone has come up with a theory and practiced it from x height being able to achieve a landing every time, but the engine doesn't give you a textbook place, time or duration to stop.

[RFguy]

It's that time-delay factor that leads to the policy of landing straight ahead with no more than 30 degree deviation no matter what you're going to hit. That's where the optium percentages are.

Yeah I was thinking about just that on my drive to the factory this morning. After pushing the nose over, there is going to be at least 5 seconds lost while you figure out "WTF is happening" and try a couple of things . meanwhile either airspeed or altitude is lost. You migth as well just get stuck into your glide. Unless there is a brick wall in front of you- in which case you are only looking for 90 deg turn etc etc

Edited September 21, 2020 by RFguy

[SplitS]

Like everything it's not clear cut. Number 1 rule DO NOT DO A STALL SPIN. Spinning in will most likely result in a very bad out come.

A turn a low altitude with low energy is high risk but if your confident in your plane, skills and nowhere else to go it may well be worth the risk.

If your choose is houses or forest you may attempt it where as if you have open farm land you would simply land straight or slight deviation in a paddock.

[Mike Gearon]

 

Practice

Several iterations (at altitude) in a Mooney 20E yielded average altitude losses in a 180° turn of:

360′ lost at 30° bank,

270′ lost at 45° bank, and

200′ lost at 60° bank.

 

The only certainty I’d have is that pulling the stick back kills you. That’s not an option. Only level or descending flight scenarios and 30 degree scan looking for the clearspot/ the softest friendliest looking spot (between the softest looking tree trunks).../ the spot that’s not putting other lives at risk. My paragliding instructor is telling me Taiwan trees are softer so I’m big on soft spots at the moment.

 

These without power obviously or not much point. What was air speed reduction

 

I’m going to practice these. Good idea. With and without power. Will do with CFI as plan.

[turboplanner]

After pushing the nose over, there is going to be at least 5 seconds lost while you figure out "WTF is happening"

The multi-second delay is before you lower the nose, unless it's done every time subconsciously. At one stage we had about two people per years killed becaise they did nothing and the aircraft just dropped from their flight altitude, sometimes over 1000' usually going into a spin. It's after you reach a stable glide that you can choose some deviation.

[facthunter]

The risk is not getting it precisely right as the consequences are not good. The duration of the turn is a prime factor usually requiring a steep banked descending turn with a significantly high ROD. You will also be landing downwind. How many of you have ever done/practiced those and can cope with the illusions.? IF your plane doesn't have a reasonably high climb out gradient achieved, even with say 1,000 feet alt you will be too far away to make it back to the field.. Your 45 knot max stall speed comes into this and makes landing near straight ahead generally not life threatening. Nev

[Old Koreelah]

What would have been the result if, instead of starting to react when he did, he sat there and counted six seconds and then tried to complete it?

... If we are going out to practice ourselves, recation time might even be 25/100 sec. Even if we decide to set a random alarm to give ourselves a surprise we are still ready.

 

Yonks ago a car pulled out in front of my new Ducati, spilling me down the tarmac. After I got the bike back on the road I started practicing how I should have reacted. For a random, no-warning trigger, I decided that each time a bird flew across the road I would treat that as a life-threatening car or kangaroo.

After a dozen such simulations it was amazing how much I could toss the Ducati about.

 

Sure wish that was transferable to my plane, but reactions are now much slower and I'm no longer bullet-proof.

Edited September 21, 2020 by Old Koreelah

[Old Koreelah]

...Several iterations (at altitude) in a Mooney 20E yielded average altitude losses in a 180° turn of:

360′ lost at 30° bank,

270′ lost at 45° bank, and

200′ lost at 60° bank.

Very useful; been a while since I did this sort of homework.

[facthunter]

I think all motorcyclists perform better with a bit of serious off road experience and be able to let the bike hang loose a bit. A slide isn't the end of the world generally unless the bike is a real lead sled.. . Co ordination is still part of it.

Regarding the mooney figures above the plane I practiced quick "course reversals" on most was the drifter You don't load the airframe up and it's surprising what can be done with it. It's very draggy so you have to do it quickly and shove the nose down a long way. I've only flown the SB 582..Nev

[Roscoe]

Well I have a story to tell about this. I have had it demonstrated to me it is possible.

 

Reading that article as a fresh student being challenged multiple times daily with engine fail drills in circuits, my feeling is that that article is very conservative and really represents flying 101 - practice your glide approaches regularly from all different situations.....

 

Now, as for "the impossible turn" :

 

While it has been drummed well and truly into me, do not turn back, since I have had more EFATO drills thrown at me than i can remember, I am aware that the math says the energy was available to do it with a bit of height. And so my instructor did an EFATO on me, and showed me that it is possible,

 

My instructor of 50 years flying experience at I think about 500 ft AGL (I think?) in still air nil wind, on the upwind climb, simulated engine failure, then put it into a steep banked (~45-60 deg) descending turn , and put it back down on the strip (downwind) ... It was an aggressive but smooth maneuver, Not once in the maneuver did the airspeed drop below about 70 kts (flaps up, Vstall=45 kts@MW).

Then he told me- while it is possible with much experience of flying and the plane, do not do this ! always choose a less hazardous option , for example if there are flat fields of Canola available....than this one.

Obviously there is a minimum amount of altitude required to execute this maneuver. That would be able to be calculated fairly easily for a particular plane and wind* .'

 

I don't think it would be possible at less than about 350 feet judging by the altitude loss, * or with much headwind (which turns into a tailwind half way round your turn back to the strip 'the wrong way')

 

Glen.

No doubt your Instructor is highly skilled and experienced, however i would have preferred that this manouvre be demonstrated at altitude as discussed in the Zimmerman article.

[Old Koreelah]

I think all motorcyclists perform better with a bit of serious off road experience and be able to let the bike hang loose a bit. A slide isn't the end of the world generally unless the bike is a real lead sled.. . Co ordination is still part of it...

Very true, Nev. Good advice that I didn't follow. I hadn't ridden a bicycle and my first ride in a motorcycle was a 650 Thunderbird, in peak hour traffic. The best road racers seem to have learned on the dirt from an early age.

[walrus]

PUSH NOSE DOWN.

 

GET TO TWICE STALL SPEED.

 

TURN HARD AND COORDINATED.

 

You MUST get to twice stall speed before you execute.

[RFguy]

Just watch your maximum manoeuvring speed.. since in the Brumby610, 2 x Vstall (clean) = Va

[Bruce Tuncks]

Just try different speeds etc at a safe altitude. I find that in my Jabiru SK, I lose about 200 ft doing a teardrop, starting at 80 knots and a simulated engine failure. You minimize the height loss by turning slow( 60 knots) and steep ( 45 degrees). You need to start the turn quickly so the first bit is climbing as you slow from 80 knots to 60 knots .

When I told an instructor this, he said it was more like 500 ft and he proceeded to show me with a spiral dive where I was scared he would rip the wings off. He got it into the yellow zone on the ASI.

In a glider, starting at 60 knots, you can do a CLIMBING teardrop finishing at 45 knots.

BUT I hasten to add that if you are slow and dopey starting the turn, you will lose your speed before you start. Further, if you are in panic mode because of the sudden quiet, you will likely stuff things up. So the advice to " choose the least worst straight ahead" is not so silly. ( straight ahead really means no more than a 15 degree turn).

[Yenn]

In the Corby I accelerate to at least 80kts low down. I tried at 3000' doing the impossible turn and found that at 80 kts in climb configuration. Shut the throttle , nose down, a good footfull of rudder and aileron to match and I couldn't see any appreciable loss of height after turning 180 degrees.

I know there must be some loss of height, but ita all happens so quickly I was lost. I still would not like to try it low down.