Impossible Turn...POSSIBLE?!

[wpbarnar]

Agree with Pete.   Roll 75+ degrees of bank, and pull back on the yoke.  Done correctly pull until you feel buffet.

The instantaneous sink rate will be higher but the time in the turn will be much less, hence less altitude lost.

Bill

[Pete M]

9 hours ago, Bob_Belville said:

Pete, you want to defend that position?

Vbg and 45 deg bank are being taught to reverse course with minimum loss of altitude. Going faster than best glide will cost more precious altitude. Banking steeper than 45 deg will require airspeed greater the best glide to avert a stall.

Geez Bob, I dont need to defend anything. I did it, close to the ground. VG's great if your'e looking for distance. We're not, we need to reverse, NOW! If you're engine quits at 600ft chances are you're still over airport property, or damn near. Do you need distance? You're not making a level turn, you're trading altitude/energy for angle.

[Pete M]

47 minutes ago, wpbarnar said:

Agree with Pete.   Roll 75+ degrees of bank, and pull back on the yoke.  Done correctly pull until you feel buffet.

The instantaneous sink rate will be higher but the time in the turn will be much less, hence less altitude lost.

Bill

Exactly, but don't buffet, very inefficent. Stay loose, let the airplane fall. Take off flaps matter, at least in my e. Nose comes around noticably quicker. 

[mike_elliott]

14 hours ago, Bob_Belville said:

Mike, I assume you've done the math on all this. 

Nope, left that part up to nerds that like to do that sort of thing. I had my fill of math skills at Brebeuf and Purdue

Quote

At Vbg and 45 deg bank it takes 15 seconds to turn 180 degs, right? 

Ill accept that, but again, you will need to be in a turn for more than 180 degrees if you plan to hit the runway you just departed from. You could land on the road under you on downwind however  add another 45 deg leg then another 45 to line up, that makes 270 deg of turning at a 45 degree bank. using your numbers that would be 330' , But Ill bet you cant do it in that. I havent seen anyone who could yet. Then again, it has been a while since I have done this practice in an E. You sure need more in a long body.

Quote

At Vbg and 45 deg bank according to the glide ratio for my E at gross weight it appears the rate of descent is about 875'/min.

Executed with precision, it seems turning back (180 degrees) can be done in ~220' of altitude. Add to that what it might take to get lined up. Your 2 45 deg turns should be a worse case. With any cross wind those turns are reduced. Then add to that whatever margin of error you like with consideration for what the terrain ahead looks like. Just don't stall it dummy! 

ISTM the key is prior planning. If I lose the engine on T.O. what am I going to do? At 1000' AGL? At 800..., 600... 400...? Monitoring the changing context should be priority one for the first minute after rotation. 

Prior planning is the key to the whole exercise. Know the altitude number you are comfortable with to turn back. Monitor that altitude on take off, Until you get there, you are in what I call the "kill zone" You have the option of going straight ahead. Once out of the kill zone, other options open up.

Practice this at altitude, dont cheat yourself by not delaying the turn a full 5 seconds after engine loss to minimize altitude loss. This isnt a contest to see how little altitude a shorty with bladders can do it in, it is an exercise to give you a SAFE number you can add your own personal minimums to in case you ever do have an engine out on take off. This happens way too often I am learning.

[Bob - S50]

If we have excess airspeed we can use it one of two ways.  We can do as Pete suggests, or we can start a level or even climbing turn at 45 degrees of bank until the speed bleeds off.  Once it does we can lower the nose to maintain best glide while continuing the turn.  We will in effect have completed some of the turn for free.  I haven't tried this yet, but it's on my list of things to do when I'm not out on a mission or with my wife.

The problem I see with using a lot of bank and max available G's is that speed is going to bleed very quickly.  So unless we are well above best glide, by probably 30 or 40 knots (120 - 130 KIAS for my plane), we probably won't get much turn done before we're down to best glide.  If we hold it too long we might stall or get well below best glide.  This will require us to really bury the nose and unload to get the speed back.  That's going to put us in a high sink rate that will require more energy to stop.

While I think it could be done as Pete suggests, for us mere mortals I think 45 degrees of bank and best glide is a more realistic option.

However, according to Prof David Rogers, for maximum performance we should be at a speed below best glide, but not much.  If my calculations are correct, for a max gross weight airplane my best glide is 91 KIAS and the speed Prof Rogers advocates would be 86 KIAS.  For those who like reading technical papers here is a link to his website:

Prof David Rogers

Scroll down and you'll find several articles about the impossible turn.

[cujet]

A little bit off topic, but still related. 

The ability to make the originating airport with a climbout engine failure (outside of the airport footprint) remains important. With enough HP,  a properly executed climbout can result in the ability to glide back to the airport with little risk. I've practiced this a number of times, as departure from Sebring, FL after midnight is risking a swamp landing and is likely not survivable. 

 

We tend to concentrate on the impossible turn, but engines can fail at any point, and failure of an engine at full power, is not limited to the immediate airport area. 

 

Edited June 1, 2019 by cujet

[Austintatious]

Guys, best glide speed is best L:D speed.  it is relevant but do not think it means that in all engin out cases it is the speed you need to fly.  "best GLIDE speed"  not  "best WHEN gliding speed"

I can tell you from experience that if you try to do a turn to a downwind landing you do not want best glide speed in all cases.   depending on a bunch of factors, in some cases you may be fast and long when you get to the ground,  just like the guy in the previously posted video.  The more wind going down the runway the worse it will be.

You would want to make a 45 degree bank turn(into wind if x wind factor exist) this bank angle provides the best ratio of turn rate to sink rate increase.  Do not increase your load factor with the turn... this means lowering the nose and giving up altitude.  Dont fret over best glide speed right now, Keep it flying. In fact, being slower has the advantage of a tighter turn. DONT STALL. (No extra load factor!!!)

 

Once you can see the landing point its time to point the nose strait at it... not halfway down the runway.. AT the numbers. 

There are a lot of variables...how good was your climb, how strong is the wind, when did the engine fail, did you feather your prop. Are your flaps already up.

  Now that you are pointing the nose strait at the runway numbers you will be able to make an easy determination of what needs to happen next.

If your airspeed is increasing, you need to start putting in drag, possibly everything you can, including speedbrakes if you have them.  you have to kill the energy.

If your airspeed is not increasing with the nose pointed AT the numbers, now target best glide and start watching to see if you are going to make the runway or not.  Once you have it made, then gear down, if possible.

 

If you airspeed is decaying with the nose pointed at the runway numbers, you are not going to make it, accept that and pick a nice crash.  Dont stall trying to hold the nose up trying to make the runway.

All of the previously poseted stuff about determining a height for this manuver still applies.

[Pete M]

4 hours ago, Bob - S50 said:

If we have excess airspeed we can use it one of two ways.  We can do as Pete suggests, or we can start a level or even climbing turn at 45 degrees of bank until the speed bleeds off.  Once it does we can lower the nose to maintain best glide while continuing the turn.  We will in effect have completed some of the turn for free.  I haven't tried this yet, but it's on my list of things to do when I'm not out on a mission or with my wife.

The problem I see with using a lot of bank and max available G's is that speed is going to bleed very quickly.  So unless we are well above best glide, by probably 30 or 40 knots (120 - 130 KIAS for my plane), we probably won't get much turn done before we're down to best glide.  If we hold it too long we might stall or get well below best glide.  This will require us to really bury the nose and unload to get the speed back.  That's going to put us in a high sink rate that will require more energy to stop.

While I think it could be done as Pete suggests, for us mere mortals I think 45 degrees of bank and best glide is a more realistic option.

However, according to Prof David Rogers, for maximum performance we should be at a speed below best glide, but not much.  If my calculations are correct, for a max gross weight airplane my best glide is 91 KIAS and the speed Prof Rogers advocates would be 86 KIAS.  For those who like reading technical papers here is a link to his website:

Prof David Rogers

Scroll down and you'll find several articles about the impossible turn.

You're not pulling any significant g in the manuever. You can't, you dont have the energy. You'll stall first. You're just guiding the airplane around its wingtip while it falls. It happens quick so you wont be falling for long. You also dont need 270dg turn. It happens in very little space. You can land opposite traffic downwind or in the flat area of the airport if you need to. Beats the trees and structures usually surrounding most airports. Would I do it below 500ft...I'm not so sure. 

[PT20J]

7 hours ago, Bob - S50 said:

If we have excess airspeed we can use it one of two ways.  We can do as Pete suggests, or we can start a level or even climbing turn at 45 degrees of bank until the speed bleeds off.  Once it does we can lower the nose to maintain best glide while continuing the turn.  We will in effect have completed some of the turn for free.  I haven't tried this yet, but it's on my list of things to do when I'm not out on a mission or with my wife.

The problem I see with using a lot of bank and max available G's is that speed is going to bleed very quickly.  So unless we are well above best glide, by probably 30 or 40 knots (120 - 130 KIAS for my plane), we probably won't get much turn done before we're down to best glide.  If we hold it too long we might stall or get well below best glide.  This will require us to really bury the nose and unload to get the speed back.  That's going to put us in a high sink rate that will require more energy to stop.

While I think it could be done as Pete suggests, for us mere mortals I think 45 degrees of bank and best glide is a more realistic option.

However, according to Prof David Rogers, for maximum performance we should be at a speed below best glide, but not much.  If my calculations are correct, for a max gross weight airplane my best glide is 91 KIAS and the speed Prof Rogers advocates would be 86 KIAS.  For those who like reading technical papers here is a link to his website:

Prof David Rogers

Scroll down and you'll find several articles about the impossible turn.

I read Dr. Roger's paper and found it interesting. I note that his original paper on the subject was published in the  AIAA Journal of Aircraft. For those unfamiliar, AIAA is a professional organization of aeronautical engineers and technical papers don't make it to publication without review.

Even without going through the math, the results make sense. Certainly, we all learned during primary training that the turn radius decreases and the turn rate increases with increasing bank angle. So if these were the only considerations, a very steep bank would be optimum for getting turned around with a minimum of altitude loss and lateral offset. But, we also should remember that power off descent rate increases with angle of bank which argues for a shallower bank. Given the two competing conditions, it makes intuitive sense that there would be an optimum somewhere between a shallow and a very steep bank angle. Dr. Rogers, using a little elementary calculus, shows the optimum bank angle to be 45 deg.

As to the airspeed, it makes sense to use a minimum sink rate speed which is lower than best glide (maximum distance speed). The turn maneuver time is short and the airplane is decelerating so going from Vy in the climb to 1.05Vs during the turn probably averages out to somewhere around the minimum sink speed. And, of course, the slower speed reduces the turn radius.

Skip

 

Edited June 1, 2019 by PT20J

[Bob - S50]

A couple more comments.

Another technique I've read about that should make the impossible turn more possible has to do with the departure.  If we depart straight ahead, lose an engine, and decide to return; the initial 180 will put us in a position offset to the side of the runway so we will have to turn more than 180 degrees (210?) and then line up with the runway, so maybe 240(?) total?  Instead of departing straight out, I've heard it suggested that we turn 30 or 45 degrees on departure.  Then when the engine quits it does two things for us: 1) since part of our flightpath was offsetting to the side of the runway, it may be a simple 210 degree (for a 30 degree offset) or 225 degree (for a 45 degree offset) turn around to line up with the runway and 2) because of trigonometry, we will not be as far past the end of the runway.  We will be the same total distance, but not as far along the extended centerline.  Keep in mind, that turns are discouraged below 400' AGL (can't remember where that's written).

Part of the reason that 45 degrees works so well is again because of trigonometry.  At 45 degrees of bank, both sin(45) and cos(45) = .707 so we are getting equal forces working to hold us up and turn us.  That totals 1.414.  With less bank (30 degrees for example) we are increasing the vertical lift component (.866) at the expense reduced turn performance (.5).  That totals just 1.366.  Same thing if we increase to 60 degrees of bank, but the numbers are reversed.  Total of 1.366.  If you increase to 90 degrees or reduce to 0 degrees you get a total of 1.0.  45 degrees just gives you the most bang for the buck.

[HRM]

This has been some great discussion, but at the end of the day, I'd love to channel Langewiesche and get his take on it. For me, it's time for a re-read of 'Stick and Rudder'.

[HRM]

7 hours ago, PT20J said:

Roger's paper

That is an excellent paper.

[FloridaMan]

Guy killed himself leaving Brooksville or Ocala in a Bravo a couple years back. His fiancé survived. He was turning back and tried to drop the gear in the turn and stalled it. Had he not tried to turn around he could’ve gone just about any direction and landed in a field. 

Mooneys do great landing in fields and nobody should be intimidated at the prospect. Remember, when the engine stops making power, the plane no longer belongs to you; it belongs to the insurance company. 

[aviatoreb]

6 hours ago, FloridaMan said:

Guy killed himself leaving Brooksville or Ocala in a Bravo a couple years back. His fiancé survived. He was turning back and tried to drop the gear in the turn and stalled it. Had he not tried to turn around he could’ve gone just about any direction and landed in a field. 

Mooneys do great landing in fields and nobody should be intimidated at the prospect. Remember, when the engine stops making power, the plane no longer belongs to you; it belongs to the insurance company. 

I agree with everything you just said and I am always looking for that straight ahead solution when briefing a departure airport.

You fly exactly the same model as me.  What do you figure is the safe turn back altitude?  Eventually one is high enough.  I have always told my self 1000ft. I figure most airports allow 150 degrees turn around to make it at least into the wide open grassy area that is the airport grounds if the runway cannot be made and then why bother unless the solutions outside the airport are non existent in an urban setting.  Thankfully my home airport is rural and I have a long ago pre-decided solution for straight ahead whether runway 24 or runway 6, and both happen to be about 20 degrees to the left of departure. Fields.

Question for the Mooney brain trust: plowed fields if you are trying to land not with the ridges of the plowing - land gear up or gear down?  Which is safer for the emergency landing, for the pilot, not worrying about the plane.

[kpaul]

9 minutes ago, aviatoreb said:

Question for the Mooney brain trust: plowed fields if you are trying to land not with the ridges of the plowing - land gear up or gear down?  Which is safer for the emergency landing, for the pilot, not worrying about the plane.

I don't think there is a one sized fits all answer here.  The gear, even if being ripped of the airframe are helping to dissipate energy.  Then you have the problem of, what if one digs in or rips of first?  Now you are in for a wild ride.

For me, in every single engine retract I have flown, unless I know the  condition of the surface (i.e. road, golf course) I am leaving the gear up.

[aviatoreb]

2 minutes ago, kpaul said:

For me, in every single engine retract I have flown, unless I know the  condition of the surface (i.e. road, golf course) I am leaving the gear up.

That's my knee jerk reaction too.

[M20F]

I just pull the chute. 

[Shadrach]

On 5/31/2019 at 11:12 PM, Bob_Belville said:

Pete, you want to defend that position?

Vbg and 45 deg bank are being taught to reverse course with minimum loss of altitude. Going faster than best glide will cost more precious altitude. Banking steeper than 45 deg will require airspeed greater the best glide to avert a stall.

Maximum turn to sink ratio is what you want. That’s what aligns the plane with the runway with the most altitude. This is basically a descending chandelle (I brain farted the term Immelman in an earlier post , but I’m reading a book about WWI tactics so forgive me). If you look at Dave Keller’s track, he flew a question mark shaped pattern back to the field and and barely stopped before runway’s end. I too have practiced the maneuver many times. My best results occurred with a very steep initial turn that progesssivle shallowed at the 90 degree mark. In my experience this results in the most rapid course reversal with the least altitude lost and the least amount of maneuvering to realign with the runway.  

Edited June 2, 2019 by Shadrach

[PTK]

1 hour ago, aviatoreb said:

plowed fields if you are trying to land not with the ridges of the plowing - land gear up or gear down?  Which is safer for the emergency landing, for the pilot, not worrying about the plane.

The two variables that determine survivability in an off airport landing are initial impact angle and speed. Both have to do with the initial impact. Not what we’re going to collide with if anything but the initial ground impact. These two variables should be to a large extent and with some planning within our control. But we need to fly it all the way to the ground wings level and control the airspeed. In doing so we minimize the excess energy that needs to be dissipated on the ground. So I wouldn’t focus as much on gear up or down. I’d focus instead on airspeed and “land” as flat as possible. In this case I’d leave gear up. Danger being I don’t come in flat and one digs in cartwheeling the airplane. The goal is to survive the initial impact.

[mike_elliott]

8 hours ago, FloridaMan said:

Guy killed himself leaving Brooksville or Ocala in a Bravo a couple years back. His fiancé survived. He was turning back and tried to drop the gear in the turn and stalled it. Had he not tried to turn around he could’ve gone just about any direction and landed in a field. 

Mooneys do great landing in fields and nobody should be intimidated at the prospect. Remember, when the engine stops making power, the plane no longer belongs to you; it belongs to the insurance company. 

THat was Ross Grant 4/10/16 in Ocala in a 231 I believe. The Mooney Summit reached out to his surviving fiancee'

[FloridaMan]

1 hour ago, aviatoreb said:

I agree with everything you just said and I am always looking for that straight ahead solution when briefing a departure airport.

You fly exactly the same model as me.  What do you figure is the safe turn back altitude?  Eventually one is high enough.  I have always told my self 1000ft. I figure most airports allow 150 degrees turn around to make it at least into the wide open grassy area that is the airport grounds if the runway cannot be made and then why bother unless the solutions outside the airport are non existent in an urban setting.  Thankfully my home airport is rural and I have a long ago pre-decided solution for straight ahead whether runway 24 or runway 6, and both happen to be about 20 degrees to the left of departure. Fields.

Question for the Mooney brain trust: plowed fields if you are trying to land not with the ridges of the plowing - land gear up or gear down?  Which is safer for the emergency landing, for the pilot, not worrying about the plane.

I have not done power off 180s in the Rocket yet. It’s something I need to practice along with going up to altitude and testing elevator authority at different trim settings and speeds. The a major variable with the rocket (and a difference between ours) is the full feathering prop. I don’t know if it’s a good idea to feather it in the air outside of an actual emergency, and even then, there exists the chance of recovering the engine and then being unable to get the prop to unfeather. 

When I had my failure in my m20f, my issue wasn’t making it to the field, it was slowing down to get there. The sight picture at the time of my realization was that I could see the end of the 10,000ft runway and the 1,000ft marks were about in the middle, so I was at 130mph at 200ft and had 2,000ft of runway underneath me. I stood on the rudder, pulled back on the yoke, loaded the wing as much as I could and dumped in full flaps; my passenger made a hand gesture towards the gear handle. I thought “good idea” (for adding drag).

In my practice with my m20f I noted that getting below 100mph before a slip would shorten my glide distance. I’ll say that in spite of that, she kept wanting to pick up speed. As I got just over the field I was back up to around 100mph. I thought “fuck it” and forced it down. It bounced and lost a lot of speed. After a couple more bounces, I’m rolling fast and the field dropped out from under me. It was a steep downsloping runoff field that, when not covered in 4ft weeds, has the appearance of a dry delta with all the little eroded channels in it. 

As I continued rolling quickly through the weeds I for a brief instant had the sobering thought regarding my own life: “shit. Is this all there is?” I also remembered being ready to dig in a wing and ground loop the airplane if necessary as the end of the field and neighborhood approached. The plane felt like it had settled on its mains so I applied the brakes and came to a stop. 

I had 805 hours total and 600 hours in the Mooney when that happened. 

While I dropped the gear to slow down, the gear ended up buffering my touch down, protecting the airplane and control surfaces, and allowing me to maintain control authority after touching down. If making it was an issue, I would keep the gear up until I was certain I had the field made and then throw in all the drag at once. 

I was trained to imagine the center of the runway as my target, not the threshold, and to make adjustments on short final. 

[FloridaMan]

To continue my thought, my answer is gear down, but try to get the mains to dig in first. If there’s something bad enough to hold a wheel, it’s also bad enough to grab a prop blade or spinner and I visualize a fast sliding plane hulk smashing itself, pivoting on the nose, putting tremendous force on the motor mount and flipping inverted lengthwise. 

[FloridaMan]

I visited the crash site where a member here had an engine failure leaving EastHampton and landed in the birch forest that surrounded the field. They escaped prior to the post impact fire that destroyed the plane, but they made it out. 

There was an M20J that resulted in two fatalities in (I think) Texas. It may the the airplane that’s involved in a current lawsuit blaming magnetos even though NTSB reported finding significant amounts of water in the fuel lines and fuel servo. Witnesses reported the pilot made a hasty start and departure, takes off and the engine sputtered. He had plenty of runway remaining. He lowered the nose and the engine regained power. He then started to climb and the engine lost power, so he stall spins it trying to make it back. 

If you lose power and there is a suitable place to land (and nowhere else if you overshoot), make sure the power doesn’t come back and land it there. 

[HRM]

When the engine quits you become ballistic (in more ways than one). I use my gear like speed brakes, when close to 120 I drop 'em and instantly I am at 120 and dropping.

Why you would lower your gear after an engine quit is beyond me unless the GUMPS sequence is so thoroughly into your mind you can't help it (engine failure is an immediate indicator that some sort of landing is imminent).

When close to the ground; i.e., shortly after TO, so many factors come into play that are working against you that I don't think you can speculate at what altitude you might be able to get the turn in. Presumably, since you are in TO phase, you have a headwind. That's helping with lift, but without an engine it's also trying to slow you to a stall. Once the turn commences it becomes a crosswind and then a tail wind. If you are basically doing the kamikaze to get back on the ground, two things are certain. You will maintain useful airspeed and you will get to the ground very quickly. At issue is where.

One thing I will point out with my E is that the engine is often off (well, idle) when I land a squeaker. Mooneys like to float and I'd be happy to take a wham, bam, thank you ma'am bouncy landing if the engine quit. Of course, with the gear up there would not be a lot of bounce 

[aviatoreb]

4 hours ago, FloridaMan said:

 

wow.  What a day you had!

Regarding feathering the prop in practice.  Once I feathered the prop (before I changed to my MT) and at idle, the engine does not have enough power to spin the feathered prop, so the engine decided to quite.  Yikes!  But I managed to restart.  Still I only did that ONCE.  But it is amazing how the airplane seems to positively jump up when changing to feathered position - you can literally feel the greater glide.