Impossible Turn...POSSIBLE?!

[Pete M]

On 6/3/2019 at 11:12 PM, carusoam said:

Thanks for the great input from those that have had the experience...

1) Thoughts on practicing 75° banks... that is just beyond the 60° normal bank that I usually limit myself to... 2g 

2) Practicing at altitude... safe, but it may be a challenge to detect some of the speed and altitude changes...

3) Has Anyone used the CloudAhoy app to capture what actually happens in the practice of this? My memory for that much detail over a few maneuvers isn't that strong...

4) How does the plane handle flying so slow, pulling 75°...  how much nose down attitude is required to avoid stalling the plane?

5) Oddly enough my POH only covers the effect of stall speeds at 60° and level flight...

 

I would really like to get more detail regarding effect of less than 1g turns... (unloading the wing)

 

PP thoughts only, just asking, not intending to fly low level aerobatics in a Mooney...

Best regards,

-a-

I realize I'm probably stating the obvious here. An airplane stalls not because you've gotten too slow but because you've exceeded the wings criticle angle of attack. I regularly turn airplanes at speeds well below vs. Vs is based on 1g. You should be at no where near 2g's in the manuever. I understand you no longer fly a short body, you have a higher wingloading so your alt loss will be greater. By the way, at VA the a/c can generate enough g to generate 3.8g's. VA, especially when light, is not much greater than vy. You can drop the nose to get the E needed prior to the mauever if necessary. I flew the mauever at well above vg because I knew I needed the e to make the two 180's I wanted to complete it. I only really needed the one 180 to land safely down wind. This doesn't require any special pilot skill just an hour of practice. One should be practiced in the art of plane handling at the edge.

Edited June 5, 2019 by Pete M

[Shadrach]

23 hours ago, Yetti said:

So the impossible turn is possible, it is not possible with the standard set of pilot skills that cannot keep from crashing performing a standard landing pattern.

 

Anecdotally speaking (I've not downloaded the NTSB data), I think Mooney pilots have a better record in the pattern pre-landing, I see more  RLOC/overuns, take off and go around incidents than the dreaded base to final stall...though it can and does happen too much.  I also think there is a culture that sees aggressive maneuvering (at altitude) as "hot dogging".  I grew up around pilots and have several in the family.  Many would never consider doing any serious maneuvering in a MOONEY.  After all it's a serious cross country machine and not designed for yanking and banking.  I disagree. If you're uncomfortable or nervous about slow flight, banks over 60°, power off descending steep turns,   accelerated stalls etc... It would be a good idea to practice those things with an an instructor.  These are not precision maneuvers, they are are more aggressive than normal flight ops but require no special skill. Learning to operate comfortably just inside margins and up to the departure from controlled flight makes one better at recognizing an impending departure from controlled flight when operations are pushed outside the norm.

[0TreeLemur]

On 5/30/2019 at 11:15 AM, HRM said:

So, apparently a new thing is the notion that the 'Impossible Turn' is indeed possible. The prophet of the concept is American Airlines ATP Brian Schiff who not only has done it, but practices it. See the attachment link for his worksheet. Apparently the FAA may be warming to the concept.

Anybody done this in their Mooney?

Possible Turn Worksheet (PDF)

Just curious- why in the Brian Schiff worksheet is the turn a 360?   Looking at the Dave Keller video, he turned approx. 225  degrees to the right then about 45 to the left to line up with the runway he landed on.  But, he could have landed straight ahead off-runway without doing that last turn.  That last turn to the left in terms of personal safety, was not necessary.  Risking an approach stall to save the insurance company some money is not my idea of a worthwhile activity.

BTW- in the category of "brushes with greatness"  Dave Keller's 1967 M20C was the next one off the assembly line after mine.  I wonder if my engine is destined to fail in the same way... 

[bonal]

37 minutes ago, Fred₂O said:

Just curious- why in the Brian Schiff worksheet is the turn a 360?   Looking at the Dave Keller video, he turned approx. 225  degrees to the right then about 45 to the left to line up with the runway he landed on.  But, he could have landed straight ahead off-runway without doing that last turn.  That last turn to the left in terms of personal safety, was not necessary.  Risking an approach stall to save the insurance company some money is not my idea of a worthwhile activity.

BTW- in the category of "brushes with greatness"  Dave Keller's 1967 M20C was the next one off the assembly line after mine.  I wonder if my engine is destined to fail in the same way... 

Yeah 220 230 to get to around 45 to the runway that's what I did as opposed to my previous post after I replayed it in my mind. I was making some power but not sure how much a conti 200 is producing at 1500 rpm with the throttle pulled to idle was probably more windmilling than hp. There are different levels of engine out and this must also be taken into account. Lots of decisions to be made in zero time.

[0TreeLemur]

1 minute ago, bonal said:

Yeah 220 230 to get to around 45 to the runway that's what I did as opposed to my previous post after I replayed it in my mind. I was making some power but not sure how much a conti 200 is producing at 1500 rpm with the throttle pulled to idle was probably more windmilling than hp. There are different levels of engine out and this must also be taken into account. Lots of decisions to be made in zero time.

I guess the 360 in Brian Schiff's example builds in a bit of conservatism, but then he recommends multiplying lost altitude by another factor of safety of 1.5.  We all want factor of safety, but in my case the propensity to land +-30 degree off straight ahead is so strongly ingrained that that is most certainly what I'll try to do.   Watching Dave Keller's video, every time the stall horn sounded I felt ill.  Back in my 172 days I remember flaring and having the stall horn go off for what seemed like an eternity before hearing the happy chirp of the tires.   In my Mooney, there are no eternities of stall horn noise.   The time from horn initiation to stall in my bird is seldom more than a couple of seconds.

[Shadrach]

6 minutes ago, Fred₂O said:

I guess the 360 in Brian Schiff's example builds in a bit of conservatism, but then he recommends multiplying lost altitude by another factor of safety of 1.5.  We all want factor of safety, but in my case the propensity to land +-30 degree off straight ahead is so strongly ingrained that that is most certainly what I'll try to do.   Watching Dave Keller's video, every time the stall horn sounded I felt ill.  Back in my 172 days I remember flaring and having the stall horn go off for what seemed like an eternity before hearing the happy chirp of the tires.   In my Mooney, there are no eternities of stall horn noise.   The time from horn initiation to stall in my bird is seldom more than a couple of seconds.

Your perception of the gap from warning to break is a measure of of how long it has taken to get from one AOA (horn) to another (break). It tells you almost nothing useful.  One can make a plane stall with almost no gap between stall and stall warning simply by accelerating the stall... Go do some slow flight and see what speed the horn comes and compare that to the speed that it breaks. That will at least tell you the speed margin in 1G level flight.  It's likely more than you think.  I always liked the progressive nature of the Cessna reed valve stall horn. The horn begins with a gentle coo progressing to a scream...much better than a binary stall vane.

[0TreeLemur]

33 minutes ago, Shadrach said:

Your perception of the gap from warning to break is a measure of of how long it has taken to get from one AOA (horn) to another (break). It tells you almost nothing useful.  One can make a plane stall with almost no gap between stall and stall warning simply by accelerating the stall... Go do some slow flight and see what speed the horn comes and compare that to the speed that it breaks. That will at least tell you the speed margin in 1G level flight.  It's likely more than you think.  I always liked the progressive nature of the Cessna reed valve stall horn. The horn begins with a gentle coo progressing to a scream...much better than a binary stall vane.

What you say is true, and I've done a lot of stall training, including accelerated stalls.   Aloft, I can make the stall horn go off all day and not actually stall.  But what I'm talking about stems from my repeated observation that in landing configuration in the flare with throttle closed, my a/c does not give much warning between stall horn initiation and stall break.  It has nothing to do with my pilotage.   It just always happens that way.  I too liked/miss the progressive nature of the Cessna stall horn.

Maybe the fact that Dave Keller didn't have the flaps down actually helped him?  When I originally watched that video  before I knew that he didn't have the flaps down, every time I heard that stall horn I thought "this is it".  In my a/c with flaps/gear down and engine not producing power, when the stall horn goes off, it is really close to a stall.  That's all I'm saying.

[PT20J]

The stall warning is adjustable. Specs and procedure are in the maintenance manual. 

[FloridaMan]

3 hours ago, Shadrach said:

Your perception of the gap from warning to break is a measure of of how long it has taken to get from one AOA (horn) to another (break). It tells you almost nothing useful.  One can make a plane stall with almost no gap between stall and stall warning simply by accelerating the stall... Go do some slow flight and see what speed the horn comes and compare that to the speed that it breaks. That will at least tell you the speed margin in 1G level flight.  It's likely more than you think.  I always liked the progressive nature of the Cessna reed valve stall horn. The horn begins with a gentle coo progressing to a scream...much better than a binary stall vane.

I've wondered how far out one must get before being unable to "catch" the stall. I think it was @jetdriven who used an example of the possibility that a pilot set on returning could be banked at 45 degrees and 20 degrees pitch down with the stall horn blaring while trying to turn back. I imagine that a stall in that attitude at 300ft AGL would end in disaster, regardless of who's at the controls. I've gone up with an acrobatics instructor who had thousands of hours of Mooney time and done aggressive stalls at 4000ft in my M20F. You can be at full power, bleed off airspeed, hold the yoke in your lap and keep the wing stalled and keep the plane right-side up with the rudder (full power stalls require almost full right rudder just before the break). It is violent, requiring significant rudder correction and the airplane's response lags and overshoots, but it does not roll over. Aggressive accelerated stalls ended up with me being immediately wings level. I don't know if it's the flight characteristics of the airplane or if I was so terrified of ending up inverted that I reacted so quickly with top rudder as to recover wings level.

If having to turn to make a target with an engine out, I've done the thought experiment that I should use top rudder to correct for centerline alignment if base-final needs to be aggressive. It makes sense to slip to align and track with the centerline of the runway, level the wings and track straight with the rudder once wings are level. If you're being pushed away from the centerline in a manner that requires a tighter turn, the temptation is to not overbank and to tighten the turn with the bottom rudder (skidding turn) since that will align you with the centerline, but only briefly, as your plane continues on its path. Continued input means more rudder and more bank, shadowing the bottom wing even more. If that bottom wing stalls, the forward CG of the normal category airplane and the stalled bottom wing means that the nose drops, the non-stalled "top" wing gains speed and lift, rolls the plane and creates a smoking hole in the ground. A side slip (top rudder) to correct centerline displacement allows for change in offset with no change in bank. If the pilot screws up and stalls with a little top rudder, provided there's not enough input to enter a snap roll, the bottom wing remains flying while the top wing drops through level and you have more time to prevent the spin with the rudder. Or, to put it another way: stall the bottom wing (skid with bottom rudder) with 60 degrees of bank and you're inverted after rolling only 30 degrees, stall the top wing (stall in a slip with top rudder) and you've got 150 degrees of roll for recovery before you end up inverted. 

I haven't tested the above theory, and hope to never have to, but it's something I've thought about. 

[Hank]

Whenever I overshoot the base-to-final turn (hey, stuff happens!), I just maintain my turn and hold it longer, until I'm point back at the runway. When aligned again, I turn towards it. With power loss, I'll just set her down anywhere I can not covered with people, buildings, trees or vehicles (in order of priority to avoid).

Holding the turn is my ingrained habit. With power, if I'm too far off I go around, but that ain't happening with a bad engine.

[0TreeLemur]

1 hour ago, PT20J said:

The stall warning is adjustable. Specs and procedure are in the maintenance manual. 

I excitedly searched through the 1980 pdf of the Maint. Manual for this procedure.   They call it the "prestall warning".   A search through the entire manual using terms "prestall", "stall warning", and "stall " found no mention of this warning adjustment.   Can you tell me the page number?  Maybe that instruction was in an SI or SB?

[PT20J]

Stall warning adjustment is covered in 27-95-00 for the M20J - not sure about others.

Stall warning should activate at not less than 5 kts nor more than 10 kts before power off stall entered when decelerating not more than 1 knot/sec from a trimmed speed of 1.5 Vs. Should be checked in all configurations. Loosen screws to adjust vane. Moving the tip approximately 1/4” changes speed by about 5 mph.

Skip

[ZuluZulu]

On 6/2/2019 at 11:02 AM, pmccand said:

I can’t believe that I missed posting this thread earlier, but I have personally performed the “Impossible Turn” as a result of total engine failure on my FIRST UNSUPERVISED SOLO!  I was at 500 feet AGL just after take off in a Cessna 150.  It was just the day before, my instructor showed me a procedure that “might save my life some day”.  Turned out to be the VERY NEXT DAY!  

BANG! No engine just after rotation and climbing through 500 feet after take off.  Declared an emergency, pushed the nose over, simultaneously dropped 10 degrees of flaps continued turn at best glide speed.

After getting the Mooney, I tried to duplicate the turn at altitude.  Take it from someone experienced at this...There is NO way in hell that the Mooney could have successfully made that maneuver at 500 feet.  NO WAY at all.  The turn can be made, but you need a LOT more altitude with the Mooney, so now when I am close to the ground, I look for something soft, flat and inexpensive straight ahead.  I still do practice the maneuver, but my decision height to turn around is now much higher than with a Cessna.

I had almost the exact same experience!  Like you, it was either my first or second solo without my instructor watching me from the ramp.  I had maybe all of 20 hours’ experience and was going to be doing pattern work in a Rotax-powered light sport.  My instructor and I had just practiced the 180 degree turn about a month earlier and we found that we’d lose about 400 feet in the maneuver.

Sure enough, I departed and reached at most 700’ AGL when the engine started running extremely rough, shaking the entire airframe, and with the fuel flow gauge almost ready to burst.  (I later concluded the automatic-altitude-compensating carburetor had become stuck and flooded the engine full-rich, as it was a warmer than normal day, although there was no actual investigation.). I initially thought I would be able to limp it around the pattern and started my left crosswind turn a little early (sorry, noise abatement!) but quickly discovered there was enough of a power loss that I wouldn’t be able to maintain altitude without trading airspeed.  So instead I declared an emergency, quickly rolled into a right turn back to the same runway, and rolled out on a perfectly aligned short final, maybe 250-300’ AGL, right at the exact maximum flap extension speed so I quickly dropped full flaps.  From there I made an uneventful landing (my first one on that runway!) and limped it back to the flight school.  I’ll never forget the rush of relief in the controller’s voice when I confirmed I didn’t need any assistance.

After that I was pretty sure I’d just passed the checkride, but it turns out the DPE has to be there for it to count.  Drat.

[Shadrach]

On 6/2/2019 at 2:02 PM, pmccand said:

BANG! No engine just after rotation and climbing through 500 feet after take off

After getting the Mooney, I tried to duplicate the turn at altitude.  Take it from someone experienced at this...There is NO way in hell that the Mooney could have successfully made that maneuver at 500 feet.  NO WAY at all.  The turn can be made, but you need a LOT more altitude with the Mooney, so now when I am close to the ground, I look for something soft, flat and inexpensive straight ahead.  I still do practice the maneuver, but my decision height to turn around is now much higher than with a Cessna.

In the C150 I trained in, very little happened “just” after rotation.  500 ft was minutes away...

I beg to differ on “the no way in hell” sentiment since there is video in this thread of a C model completing the turn at well under 500ft.

[mike_elliott]

3 hours ago, Shadrach said:

C model completing the turn at well under 500ft

Dave told me he was higher, and why he made the turn.

[bonal]

This reminds me of a flight when I was doing my private training with my instructor and we were at about 5000 ft and a couple miles east of UKI which is at about 600 ft elevation. My instructor pulled the power to my 150 and left it to me to do an emergency landing. The runway was to my left as we were headed north more or less parallel to runway heading. As I made for the runway I felt we were way too high so I executed a 360 turn in the area of the down wind to base part of the pattern. By the time I had things lined up I knew we were going to end up short.  My instructor gave me back my engine and asked me why I did what I did. This is another example of how important it is to learn how your bird performs in all scenarios. Once we lose the big fan out front we only get one shot at getting it down safely.

[steingar]

In my Cherokee I used to go find airstrips devoid of traffic and practice power off landings.  I'd put the aircraft 3 or 4K feet in the air and shut down the power (it went on here and there on the descent).  Rule was I had to have a full stall landing onto first third of the runway.  If I didn't I had to do it again.  I should try doing that in the Mooney, you really get to know your airplane's energy.

[Shadrach]

7 hours ago, mike_elliott said:

Dave told me he was higher, and why he made the turn.

Interesting. In the video he stated between 450 and 500’. When you watch the video you can see his recording equipment had a timer. He lifted off at 2:34:59. The audible separation of the cylinder occurred at 2:35:26. So he lifted off, raised the gear, accelerated to Vy and climbed >500’  in 27 secs.  I know it was a cold day but his recollection in the video seems more plausible than what he told you privately.

[mike_elliott]

23 minutes ago, Shadrach said:

 I know it was a cold day but his recollection in the video seems more plausible than what he told you privately.

Actually, he said it to a whole group at the Mooney Caravan ( in 2006 I believe), not just me privately. Far be it for me to disbelieve him or speculate on what altitude it was in contradiction to him. If he would have ADS-B back then, we could tell him he did a more remarkable job than he did possibly.

[EricJ]

12 hours ago, Shadrach said:

In the C150 I trained in, very little happened “just” after rotation.  500 ft was minutes away...

I beg to differ on “the no way in hell” sentiment since there is video in this thread of a C model completing the turn at well under 500ft.

A friend did it while instructing in a C150 after it swallowed a bunch of water.   So a gutless C150 with two people in it, and she still made the turn and got it on the runway intact.   I don't recall the details of how high she was, unfortunately.

 

[Shadrach]

4 hours ago, mike_elliott said:

Actually, he said it to a whole group at the Mooney Caravan ( in 2006 I believe), not just me privately. Far be it for me to disbelieve him or speculate on what altitude it was in contradiction to him. If he would have ADS-B back then, we could tell him he did a more remarkable job than he did possibly.

I think he did a remarkable job no matter the altitude. Given you’ve had several interactions with him and you said he told you, I assumed it was a one on one.

Edited June 7, 2019 by Shadrach

[Shadrach]

9 hours ago, pmccand said:

As a side note to my earlier story of having to make an impossible turn on my first unsupervised solo, when practicing the turn around in a Cessna 150, we found we could execute the 180 degree turn and lose only 50 feet (yeah, FIFTY) vertical feet in the process.  Using exactly the same procedures, ( and using only my memory as a reference) the best we could do in the short body Mooney was 250 - 300 feet loss of vertical.  The other factors to consider is that the Mooney has travelled much farther from the airport, as it is going much faster than a 150 on climb and the turn radius is many times larger.  So when I limit myself to “never turn around under 500”, that is based on allowance for things to go wrong or fudge factors such as decision making times added into the mix.

One other thing why it is important to learn about rate of descents in power-off turns is knowing what to do if you lose power at high altitudes directly above the airport.  Here, you are not trying to squeeze the maximum glide distance out of your bird, rather you want to know how many more “spiraling” turns you can make in order to be at the correct altitude when lining up for final with no engine.  In a Cessna, its no big deal as it looses only a hundred feet or so per turn, whereas a Mooney looses 2 or 3 x that, AND the radius of that turn will be much greater.  I find it difficult to instinctively know how to plan for a successful landing at altitude directly over an airport with the Mooney. Maybe someone can enlighten me on how to make power-off descent controlled turn decisions to successfully make it back to the airport when at cruise altitude feet directly ABOVE the runway.  How do you know if you have enough altitude as you approach the airport that you need to add that  ONE EXTRA TURN ... or not?  I really DON’T want that final turn to become an IMPOSSIBLE TURN because I am too low when I get there.

I just did this during my last FR from 5000’ to threshold. Use a high key and low key approach. I use the end of the runway as my high key (1000’agl). I try to hit the high key perpendicular to the downwind. I then as I pass over the runway I make a constant 270 from there using base to final as low key (500’agl). I use 120mph as a target speed and reduce or increase as needed. Gear comes out when runway is assured. This was at KFFR in VA. The runway is 3007’. I had to slip after turning final to kill speed and energy but we would have made and stayed on the runway. Had the winds been 20kts, I would have needed a lot of that surplus energy.  It’s a good maneuver to practice and it’s fun.  There are no hard and fast rules as to where your high and low key is or how high they are. You can develop your own system. They merely serve as a reference to let you know how you're managing your energy.

[HRM]

On 6/5/2019 at 1:05 PM, Fred₂O said:

Just curious- why in the Brian Schiff worksheet is the turn a 360?

It's "worse case scenario" and fits with the classic description of the 'Impossible Turn'; i.e. that as you depart on heading, you lose an engine and you loop 360º back to your departure RWY. Of course, all the practice is at high altitude. Frankly, I like what <someone here> said, that the airport in general is full of all sorts of good landing places, no need to necessarily return from whence you came. Once you declare an emergency the airport is pretty much yours. The key is to not panic and not feel that you cannot make the turn (under any circumstance). Once again, a 'seat of the pants' Stick and Rudder thing.

[aviatoreb]

22 minutes ago, HRM said:

It's "worse case scenario" and fits with the classic description of the 'Impossible Turn'; i.e. that as you depart on heading, you lose an engine and you loop 360º back to your departure RWY. Of course, all the practice is at high altitude. Frankly, I like what <someone here> said, that the airport in general is full of all sorts of good landing places, no need to necessarily return from whence you came. Once you declare an emergency the airport is pretty much yours. The key is to not panic and not feel that you cannot make the turn (under any circumstance). Once again, a 'seat of the pants' Stick and Rudder thing.

..I think you meant loop 180.

Anyway I get your point and I was thinking the same thing.  If one had to turn back vs crashing into an urban environment straight ahead, then 

-in most single runway environments a partial turn back might be enough - say 150 degrees back - to at least land in the grassy part of the airport from which you came.

-in a bigger airport with two runways, and long runways, say 5000ft 'ish, even a 70, 80 or 90 degree turn might be enough to land in the airport environment on grass.

ANd landing in unimproved grass may well be damaging to the airplane but better chance less damaging to the humans in the airplane.  

[HRM]

On 6/11/2019 at 2:59 PM, aviatoreb said:

..I think you meant loop 180.

 

I thought hard on that (original post quote). When you think about it, it's a 360 all the way around (like a hairpin) even though you are 180º back the same way you came.

No matter, we all know what it is in the end--terrifying with no engine!