The (im)possible turn - revisited with Doug Rozendaal

Discussion in 'Pilot Training' started by Martin Pauly, May 29, 2021.

  1. Martin Pauly

    Martin Pauly Pre-takeoff checklist PoA Supporter

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    Whether or not you agree with the conclusions stated in this video, odds are you can learn a thing or two from Doug’s systematic and logical risk analysis and risk management expressed in this latest video I recorded with him. When (yes - when, not if) the engine stops making power, what really is the response we can choose which has the highest probability of survival? And how does this differ between right after take-off and cruise?

     
    Last edited: May 29, 2021
  2. nauga

    nauga Administrator Management Council Member PoA Supporter

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    buttweight.png

    Nauga,
    who really appreciates an abstract
     
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  3. TWD87

    TWD87 Filing Flight Plan

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    Really enjoyed that video. Thank you. I need to re evaluate some of my pre takeoff planning and will look for the pre departure brief video of yours that he mentioned as well. Thanks again!
     
  4. Martin Pauly

    Martin Pauly Pre-takeoff checklist PoA Supporter

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    What can I say - you got me there. :)
    Thanks for pointing it out - I fixed it in the original post.

    - Martin
     
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  5. PaulS

    PaulS Touchdown! Greaser!

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    Great video Martin, worth the watch. Can tell you put a lot of effort into these and it shows.
     
  6. Initial Fix

    Initial Fix Pre-takeoff checklist

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    Enjoyed the video, and especially Doug’s great way of breaking down the risk management.
     
  7. brcase

    brcase Pattern Altitude

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    Excellent discussion about the impossible turn, and evaluating the risks of engine failure.

    Some points I agree and would like to emphasize were..
    Practicing the impossible turn at altitude is not realistic
    The only way to make the impossible turn possible is to practice it regularly and be extremely confident it is the best option.
    Trees are usually a good emergency option if flat surface is not available.
    Planes that arrive under control have survivors.
    The Power of 180 should be practiced a regularly, as it is the most likely maneuver you will need to do after a power failure.
    We should be be practicing power failures from cruising altitude. Can you get to the downwind for a normal power off landing after a power failure? A downwind even when landing off airport is usually a good idea.

    Points I have some disagreement on.
    Idle thrust vs power off makes a big difference. My experience has been this is not the case, I have never been able to tell more than a minor difference in glide performance. But perhaps that is because I try not to practice emergency procedures right at the edge of the performance envelope. This means the difference is easily absorbed by the performance margins of the maneuvers I am performing.
    My opinion is if idle thrust vs power makes a difference then you are probably flying closer to the edge of the performance envelope than you should be in an emergency.
     
  8. write-stuff

    write-stuff En-Route

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    A nicely-done entry into the "impossible turn" discussion, Martin.
     
  9. AggieMike88

    AggieMike88 Touchdown! Greaser! PoA Supporter

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    The original "I don't know it all" of aviation.
    You have an instructional treasure in Doug. I enjoy his speaking and presentation method.

    I hope the two of you will cover additional topics in the future.
     
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  10. Silvaire

    Silvaire En-Route

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    I agree with pretty much all that Doug said but the "when, not if" statement is a bit misleading. Yes, eventually sometime, somewhere some engine is going to quit in flight but to balance that there are thousands upon thousands of engines out there both past and present that have never failed and never will.
     
  11. Martin Pauly

    Martin Pauly Pre-takeoff checklist PoA Supporter

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    My experience has been different from yours. If you maintain best glide speed with idle thrust and note the vertical speed, then cut off the mixture and (while still maintaining best glide speed) again note vertical speed, there's always been a significant difference. Not a factor of two, but 20% to 30%. Which means if you can just barely complete a turn-back with the engine at idle, you WILL be short if you try the same thing if your engine makes no power.

    I'd be curious to know what results you see when you say there is only a minor difference. What airframe, what engine and prop? And what vertical speed did you observe at idle vs. cut-off, while maintaining the same airspeed?

    Regards,
    Martin
     
  12. kyleb

    kyleb Final Approach

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    Even better, if the odds of an engine failure are 1 in 10,000 hours, the odds of an engine failing in the 60 seconds between brake release and an altitude that give you options are miniscule. Still, that minute may be the riskiest minute of most flights.
     
  13. brcase

    brcase Pattern Altitude

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    I have experimented with a number of 120/140/150/152/172/182 Cessnas and a few Cherokee 140/160’s. To be fair we are probably looking at two different things. I was less interested in what the actual performance drop might be and more interested in how realistic our emergency approach and landing training is. So most of my experimentation has been either performing power off 180 approaches or more often something more like the SFO (simulated flame out) approaches he mentioned.
    What I observed is was there was usually not a perceivable difference in flying these approaches with a windmilling propeller vs idling engine.

    I have not done much experimenting with heavier aircraft like the Viking or Cherokee 6, But they come down so fast even at idle, I suspect there probably isn’t much noticeable difference there either.

    Brian
     
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  14. Huckster79

    Huckster79 Pattern Altitude

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    Excellent discussion and really logical viewpoint laid out.
     
  15. Tools

    Tools Pre-takeoff checklist

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    A huge take away for me, and a point I’ve always preached, is the difference between a power loss, and engine loss.

    I personally feel a power loss CAN be more dangerous because you’re less likely to give it the respect it deserves. Partially because in a power loss, how do you really know HOW MUCH power you lost? Committing to an off airport landing is hard to do when the gages look normal and you hear noise...

    Agreed, no right answer sitting here in a chair, but a good thing to think about.

    Great video and interview. Thanks!

    Tools
     
  16. Tools

    Tools Pre-takeoff checklist

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    More food for thought. Turbo props. Lose your engine, prop feathers on its own. How is this a problem? Flying jumpers, I roll onto SHORT final at 2500 agl and 150 kts. If I lose my engine then, prop is gonna feather and now I’m looking at over running a 3500’ runway.

    Just thinking about this one day and now I fly differently than I was shown.

    Another food for thought... I now believe in sidestepping off the runway ASAP. As soon as a safe landing can no longer be made, start displacing ANYWHERE. That gives you angles on a return to the runway scenario.

    Tools
     
  17. write-stuff

    write-stuff En-Route

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    It's more like 90 seconds, but it is still a risk that can be mitigated with training and planning. These types of failure don't happen often, but they aren't rare either. It's happened to me twice.
     
  18. write-stuff

    write-stuff En-Route

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    And yes, there is a big difference between an idling prop (simulation) and a windmilling prop (the real deal). We've only done the math in a 172, but you will glide about 20% further with an idling prop.
     
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  19. kyleb

    kyleb Final Approach

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    Depends on the airplane. I was trying to offer a generic figure. In my airplane, the window of vulnerability is probably <30 seconds. The first 15-20 seconds after brake release, the remaining runway is the default. After the next 30 seconds, I'm at 400', doing >2x stall speed. If someone is flying a grossed out Cherokee, the period of vulnerability would probably approach 2 minutes - after the option of using the remaining runway is lost, but before the airplane reaches pattern altitude. The duration of the exposure is very much driven by the aircraft's stall speed and the excess energy available during the acceleration/climb phase.
     
    Last edited: May 31, 2021
  20. PaulS

    PaulS Touchdown! Greaser!

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    Every flight is a window of vulnerability, the key is to try to be prepared for it and do the appropriate thing at the appropriate time. I think the appropriate thing varies by airplane.
     
  21. steingar

    steingar Taxi to Parking

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    Used to be my departure briefing was straight ahead. Nothing but fields, made sense. Now my airport is in the middle of a suburb. My brief is to make the turn. My thinking is the worst possible outcome is trying to land that neighborhood, I put me, my pax and folks on the ground in jeopardy. If I make the turn, don’t make it all the way around and have to try and land a street or parking lot, it isn’t any worse. There’s a farm on one side of the airport, if I make that I’m good. Won’t feel bad about hitting a cow. And my airport has parallel runways, so I only have to turn 180. Heck all I really have to do is make it to the airport environment. If I land the grass next to the runway it’s all good. That, and I fly a complex single that will glide well with the gear stowed. Don’t see the point of practicing it, you just can’t safely duplicate the situation outside a simulator.
     
  22. Silvaire

    Silvaire En-Route

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    The main point of it is, as was discussed, that doing an extreme maneuver under stress at low altitude with your focus on a ground reference is a recipe for a spin. It happens even to seasoned pilots. Your track across the ground may look perfect but the ball is slammed over to one side and you're slow. You don't know it because you're looking at the ground. For this reason it's risky to continually practice this at the edge just to prove to yourself that you can do it or to try embed the muscle-memory skills that would allow you to instantly enact that course of action in an actual emergency. Because when you practice this is what you are doing, you are instantly taking a preplanned course of action. when you line up and push in the throttle you already know what you are going to do. There's nothing to figure out.
     
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  23. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    During my total loss of power, I mistook the windmilling of the prop for a partial power loss. My misconception wasn't corrected until the prop stopped dead on the runway.
     
  24. Martin Pauly

    Martin Pauly Pre-takeoff checklist PoA Supporter

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    It sounds and feels surprisingly similar, doesn't it? Which also explains why the step of identifying the dead engine is so critical if one fails on a multi-engine aircraft.

    - Martin
     
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  25. MauleSkinner

    MauleSkinner Final Approach

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    And that, boys and girls, is what we call “correlation”. ;)
     
  26. idahoflier

    idahoflier Cleared for Takeoff

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    Excellent video! Thanks for creating and sharing!
     
  27. Torque beast

    Torque beast Pre-takeoff checklist

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    Great video Martin, a lot of good discussions in there with several points that are eye opening


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