Impossible turn practice at 500ft

Discussion in 'Flight Following' started by motoadve, Nov 21, 2017.

  1. denverpilot

    denverpilot Taxi to Parking

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    I was thinking of it in simpler terms. Let’s say Vy is 70 and you take off in a 70 knot headwind for silliness sake.

    You never went anywhere. You’re still over the runway. So getting back to the runway isn’t the problem. Getting down is.

    Now no-wind, your idea is correct I think. The total distance to make the turn is much longer than then straight line departure.

    There’s a point where these two extremes cross, I assume. But, I haven’t run the numbers.

    I think Mr Excel over there, Clark, could probably make a pretty graph of it. Ha.
     
  2. Salty

    Salty Pattern Altitude

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    In your new example, when the engine shuts off you immedialty start drifting behind the airport if you turn for the glide. I think it proves my point.
     
  3. Palmpilot

    Palmpilot Touchdown! Greaser!

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    If your ground speed becomes negative, there's no need to turn. I don't think that tells us much about what you need to do when you're taking off in the type of conditions that most GA pilots would consider acceptable.
     
  4. denverpilot

    denverpilot Taxi to Parking

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    Perhaps I don’t understand your point, then. Don’t turn, just land.

    That’s what I meant about there being a crossing point between the two. In light winds you end up too far away. In heavy winds you didn’t get far enough. In between somewhere there’s a sweet spot where that turn is literally no big deal and out at the edges it’s deadly.

    But I’ll have to think about this tomorrow. Or later.

    Frankly, in reality if there’s a land-able spot ahead, I’m going there. That’s the most practical. But the video shows with the right gear (note he does have an AoA indicator — it’s that little reticule thing on the left side of the glareshield) and the right prep and practice, it’s “doable” to return.

    It’s just not the best option for most airplanes and most pilots in most weather and runway cases. But I’ll couch it and say in SOME specific cases it’s fine.

    Looking at the emotional reactions above, a great many folks aren’t mentally ready for such a thing. Fear goes away with knowledge, but this is not an area of knowledge that gets taught much, because of that whole “most” thing about the specific cases.

    Training tends to focus on the MOST likely ways to survive before other stuff. You wouldn’t want to teach what he’s doing in the video as the FIRST option, it would be very bad for primacy.

    Doing from 1000’? Sure.

    The glider folks do it. They have a much much higher glide ratio so they do it from altitudes us spamcan drivers shake our heads at. Not only do they do it, it’s part of their practical test.

    FAA would NEVER make a low altitude return mandatory on a powered aircraft practical test — just to show how odd the test creation process is. It’s considered life saving in a glider but not important enough to test in a powered airplane.

    Something is a little off there.
     
  5. Palmpilot

    Palmpilot Touchdown! Greaser!

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    As you mentioned, the glide ratios are much different. That dramatically affects the odds of success. Considering all the factors that enter into whether a powered airplane can succeed in a given set of circumstances, coming up with a robust system for airplane pilots to make that determination is not easy. Given that difficulty, I suspect that the FAA's stance is more likely to be based on a belief that requiring it would do more harm than good, rather than thinking it's unimportant.
     
  6. denverpilot

    denverpilot Taxi to Parking

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    True. And good point. Risk management.
     
  7. nauga

    nauga Pattern Altitude

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    1) Nauga is not a professional test pilot - I have done some test flying for my own stuff and in my own interest, but that's not what pays the bills :)

    2) It's gotten to the point where I try to stay out of these threads because there's typically too much shouting and not enough listening, when the answers are out there for anyone who cares to do their homework. Since Prof. Rogers' paper came up again I *will* give a one-or-two line summary of research documented in AIAA papers that I think is particularly relevant to GA. It's not by any means comprehensive but it will give you a good start:

    Rogers (AIAA Journal of Aircraft Vol. 32) considers a steady turn and shows the mathematical minimum for altitude loss in gliding turns.
    Jett (AIAA-82-0406) presents results of a piloted simulation study which accounts for reaction time and handling qualities. I don't recall him expressly developing minima beyond what Rogers developed.
    Hyde (AIAA-2005-5897) presents trajectory optimization results for dynamic maneuvering, considering variations in speed at the time of power loss with considerations for reaction time and model uncertainty but not handling qualities or execution.
    I believe all 3 consider the effect of winds, but I'd have to review Jett to be sure about that one.

    Brinkman and Visser (AIAA 2007-252) also presented trajectory optimization, but using a different method and a much higher-performance model. This one I don't find as applicable to GA but the results are similar.

    I don't believe *any* of them suggest that this type of maneuvering should be done casually. At least two and probably all of the papers were intended to show what was *possible*, not what was *practical*. I spoke at length with Prof. Rogers about this not long after his paper came out and I know Hyde well. Jett I only passed in the hallways.

    Nauga,
    who did his homework
     
  8. Palmpilot

    Palmpilot Touchdown! Greaser!

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  9. Palmpilot

    Palmpilot Touchdown! Greaser!

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    A local instructor and engineer has worked out methods of calculating what climb performance one needs to see under existing conditions in order to have a chance of making a turnback successfully. Under his method, rather than trying to predict the plane's performance, the pilot watches to see whether the performance needed is being achieved. I don't think he has ever published it, but I summarized his method in the following post:

    https://www.pilotsofamerica.com/com...the-impossible-turn.35794/page-6#post-1207435

    As I mentioned before, I'm not advocating for or against attempting turnbacks.
     
  10. Sundancer

    Sundancer Pattern Altitude

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    Outside the academic/armchair discussion, my real world take was I'd probably turn back at or above 400 or 500 feet. . .if given bad options off the airport, like boulder fields, a wind farm, or a outdoor gathering of Democrats.

    Five knots either way, or 10 degrees of bank either way, doesn't matter much in a 172. And you can put a 172 in a driveway and walk away, if necessary. At some point, runway made or not, I would roll wings level and fly it under control to touchdown, just like you would if you decided not to turn back. So, I figured I'd get it pointed back at the airport ASAP, then decide if the runway was reachable, and if not, pick another reasonably flat surface. Just don't stall. . .

    I'm certain I didn't achieve the best performance possible (I'm not a test pilot or a pro); I was so attentive to not reaching a high AOA, that I'm sure spent a lot of the time in the turns at a less than optimal AOA. I imagine it could be done (in a 172) from a lower turn-back altitude, so the 400-500 AGL is my personal limit; a bit lower in a stronger wind, a bit higher in a lighter wind.

    But I see the logic in forging on straight ahead, looking for the best place 30 degrees or so, either side of the nose. Especially in a fixed gear single with very low touchdown speed, like a 172 - if you keep the wing flying, you'll probably survive the landing in a 172. And I'm not really sure what I'd do, real world; might go conservative, though my home-drome doesn't offer good options off-airport on either runway heading.
     
  11. denverpilot

    denverpilot Taxi to Parking

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    Thanks for the references. More stuff for the reading list.
     
  12. Lndwarrior

    Lndwarrior Pre-takeoff checklist

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    Boy this crow tastes great!....

    So after commenting a couple of days ago about how the OP would be a better pilot for this exercise - a guy I know was doing exactly the same thing this weekend.

    He too had a tremendous amount of experience AND his engine was running fine. He also was practicing the impossible turn under real world (take-off) conditions (not at altitude). He stalled it at 20 feet, had no time to recover - and bent the crap out of one of his gear. He got very lucky that he,or the plane, wasn't hurt worse.

    If I had ever considered trying this myself, it is now off the table.
     
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  13. Tarheelpilot

    Tarheelpilot Pattern Altitude

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    Some of the best pilots I know have had their bad days as well.

    I find myself vacillating on this topic. All I can say with certainty is we all have to make our own decisions regarding risk and the amount we are willing to assume while flying. It’s a moving target and sometimes what is safe today will be not so safe tomorrow.
     
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  14. Tantalum

    Tantalum Pattern Altitude

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    Something like this is probably best demonstrated in AATD or some other device. The lowest we ever practiced this maneuver was 1,000 AGL and the amount of altitude you lose making a 180 is impressive.. especially if you factor in "less than perfect" flying because of stress, etc., or that 3-4 second denial that someone else mentioned

    I'm a big fan of practicing emergencies often and as realistically as possible, but something like this toes the edge of the line I would say. Maybe not as crazy as setting yourself on fire to practice inflight fires but it's not far off the mark. 500 AGL doesn't give a lot of room for error. Theoretically possible, yes, since a 360 usually results in about 1,000 ft loss of altitude, but theory is not always practice.. plus the 180 turns you around, but you're still going to have to do some maneuvering to get to the runway, which will use up your energy as well

    My other thought on this (and I could be wrong), but, lets say you practice this over and over again and get really good at it. Then one day you're departing an airport and have a power failure at say, 400 AGL... there's a big field in front of you, but you try the turn since "I've done this a dozen times before, this will just need to be a little tighter" and in the process you bend your plane (or yourself) up pretty good.. or maybe you are at 500 ft but took off with a slight downwind and can't make it, or maybe you were at 600 ft but at this uncontrolled airport someone is taking off behind you.. that field is now a better option than your muscle memory of turning around

    My own rule has pretty much always been... unless I am pattern altitude or flying some kind of ODP that puts me right over the airport at low altitude I generally am going to be looking somewhere infront of me to land

    Or maybe I'm just a nervous nelly and the more experienced folks on here can nail this maneuver without much trouble
     
  15. mryan75

    mryan75 Pre-takeoff checklist

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    It is an insane training at that low altitude. I have a friend whose teacher used to do this. He insisted it could be done at altitudes as low as 200 feet AGL, and he would teach it at those altitudes. The other instructors vehemently disagreed and thought it was reckless.

    Here is the NTSB report when the instructor killed himself trying to do it for real:

    https://app.ntsb.gov/pdfgenerator/R...tID=20150815X21004&AKey=1&RType=HTML&IType=FA

    Do yourself a favor and don’t try this anymore.
     
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  16. Eric Gleason

    Eric Gleason Pre-takeoff checklist

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    If you're practicing the maneuver at altitude, then I wouldn't call you a nervous nellie. I'd say that this is something that should be practiced regularly at altitude, and occasionally from an actual take off scenario, because it does look different closer to the ground. Obviously, there is more risk involved, and that has to be managed.

    Part of the goal of practicing is to find out what your performance and the airplane performance actually is, and that drives your planning. If you know that you lose (for example) 300 feet in the turn and 200 feet to glide back to the runway, then you know that you don't do this in an emergency below 500'. There's no "I'm only at 400', so I'll just turn tighter and pray." Your plan is "If the engine fails below 500', I'll turn no more than 90 degrees to find a clearing. If it fails above 500', I'll turn into the wind and return to the runway."
     
  17. Palmpilot

    Palmpilot Touchdown! Greaser!

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    A problem with that method is that you CAN'T know that it takes you "200 feet to glide back to the runway," because that number varies with wind, density altitude, runway length, etc.
     
  18. mryan75

    mryan75 Pre-takeoff checklist

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    Also, what you’re doing is not the impossible turn. It’s the “230 HP engine running at 1200 RPM with an instructor right next to me turn”. Get to where you were on the first one, pull the red knob all the way out, then tell me how successful your “impossible turn” practice is.
     
  19. kyleb

    kyleb En-Route

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    My personal practice on this has always stopped at "runway made, apply power and go around". There's no need to continue the maneuver to the ground - it invites trouble if your margins are thin. All I'm trying to prove is that I can get back to the runway environment under control.
     
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  20. Eric Gleason

    Eric Gleason Pre-takeoff checklist

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    Was being brief for the sake of clarity. You certainly can figure out what that number is, in the same way that you can know how much runway you need for takeoff under different conditions.
     
  21. Tantalum

    Tantalum Pattern Altitude

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    You could, but I doubt most GA pilots are doing this. Heck, half the people I see taking off don't even bother with a runup, and many people I fly with don't bother with a take off brief. I've asked people "if the engine quits at 300 what are they doing?" The "find a suitable place to land ahead straight ahead" is too vague and textbook for me. If it is your home airport (or even if not) you should know where the highways, fields, etc. are so you are not guessing at that low altitude

    Everybody has different minimums though. But I think I'm with @mryan75 and some of the others. I wouldn't try it.
     
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  22. Eric Gleason

    Eric Gleason Pre-takeoff checklist

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    The take off brief is somewhat rare (mine is usually informal and in my head), but skipping a runup surprises me. Skipping the runup is or the exception than the rule from what I've seen.

    I
    I'm on board with all of this. In fact, knowing the options at my home airport are what got me seriously thinking about this, since there aren't many options. There's either development or trees in pretty much every direction, so if you can't make it back to the runway you're just going to have to try not to hit something head-on.
     
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  23. Tantalum

    Tantalum Pattern Altitude

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    same here, but I have asked people who give underwhelming responses. Others I've definitely learned from. I used to do the same "find somewhere suitable ahead" and then I flew with someone who new the roads and fields, so I adapted it into mine

    Yeah, so far I've seen it happen three times, not a lot, but enough to surprise me.

    First time was me.. back as a student on a long XC.. tower asked if I wanted to do a runup and I said yes and they let me 360 it on the runway back to runup area. I never forgot again because it scared me that I totally missed it

    Second time was not me, out here in SoCal, again tower asked a plane if they wanted to do a runup and the guy said "no we're just staying in the pattern" - which was an odd response but w.e.

    Third time uncontrolled airport. Guy had a 210 that looked like something out of mad max. Yellow sun bleached windows, definitely original paint, and I can only imagine what he had inside. Saw him power up, taxi out, and take off. The only radio he called was to me as he approached me in the runup area. Asked me "are you taking off?" and I said "no we're going to do a runup first" and he zipped by, onto the runway, and off he went. To each their own
     
  24. mryan75

    mryan75 Pre-takeoff checklist

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    I knew someone who used to do that. He’s dead as well.
     
  25. denverpilot

    denverpilot Taxi to Parking

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    I truly hope your assertion of “most” is wrong. Especially the run-up. :-(
     
  26. Tantalum

    Tantalum Pattern Altitude

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    I hope so too.. I mentioned in another post that I've seen a handful of skipped runups, and that's in 15 years..

    It did catch my ears though, a few times recently when we picked up our taxi clearance from busier airports ground would ask if we'd be doing a runup, I thought that was odd.. maybe they just wanted to know how much time they had to get our clearance, but also made me think that there must be people out there who just get out and go

    Hope I'm wrong on the takeoff briefing too, and I trust most people do a quick mental check, but in my mind that's the most critical phase of the flight, that first 200-300 feet when you're climbing away from an airport.. can't really afford to phone it in
     
  27. denverpilot

    denverpilot Taxi to Parking

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    More controversial than run-ups is people who say, “I just flew it, no need for a pre-flight...” I had a CFI do that once to me, so I told him if he’d like to get in and be comfortable, I’d be along in a minute.

    Considering I’ve found things wrong on both preflight right after a flight (busted wheel pant cuff) and run-up (spark plug connector cracked and fell all the way off sometime in the flight before, and was found by one cylinder completely gone on the Left mag setting), folks who skip things can do what they like, but I won’t be doing it.

    Even if it has to be a rolling run-up (not smart) that mag switch is getting flipped and even if it’s a downpour, I’m walking around the airplane.

    Skipping things rarely leads to anything good.
     
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  28. UngaWunga

    UngaWunga Cleared for Takeoff

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  29. denverpilot

    denverpilot Taxi to Parking

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    Paul is freaking hilarious.

    Watch the sign in the back of the plane over his left shoulder (right side of the video) carefully between cuts.

    And “Fred E. Tilton Sleep Apnea Center” on the graphic of things not to crash into... Bwahaha! Damn that’s funny. Lawyer’s kids, too.

    Much more subtle than his famous epaulets video, but awesome.