Do You Pitch Up First For Best Glide?

Discussion in 'Pilot Training' started by Sinistar, Nov 19, 2017.

  1. pigpenracing

    pigpenracing Pattern Altitude

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    It's on the biplane forum. Crank broke in half.
     
  2. write-stuff

    write-stuff En-Route

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    Maintain altitude until Vbg, then trim. And like Mark said, all the time looking for a place to land.
     
  3. nauga

    nauga Pattern Altitude PoA Supporter

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    Found a math error :rolleyes:
    For the 172-like model there is a slight advantage to climbing at some reasonable rate to max range glide, which seems intuitive. I didn't go this far, but I expect there is a crossover with climb angle even if you could pushover instantaneously to max range glide.

    That being said, reduced workload will also probably give you better results, so not horsing the airplane around might be the best option.

    I might take issue with the wording but we're mostly in agreement here. Don't forget the additional deceleration term due to gravity in a climb. Otherwise this simplification will tell you that best results are with a min drag climb, which is zero lift and a vertical climb, to best glide.

    Absolutely agreed.

    There might even be a few of them here ;)

    Nauga,
    who knows 'trust but verify' works for both nukes and NATOPS.
     
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  4. brcase

    brcase Cleared for Takeoff

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    This past week I have done some testing on the "roll the Trim Back tactic".
    I tried it in a C-172XP with 2 people a front, a C-152 with 2 people and a C-172N with 3 people on board.
    Rolling trim all the way back with 10 degrees of flaps or less after a power failure resulted in reasonably close to the best glide speed. I guess this is what the proponents of this method actually say this does. This works ok until you either add power for a recovery from practicing or after resolving the cause of the power loss or you add more flaps. The 172's with full flaps and the the trim full back produced about a 50kt glide, this Ok until you go to flare for your landing and you have no energy to stop the descent. You will need to either re-trim for landing or push the nose down to gain some speed for the flare.
    I also found it takes a lot of turns of the trim to go to full up trim. I found this distracting and takes a fair amount of time that I could be using for either attempting a restart or setting up for my approach.

    Brian
    CFIIG/ASEL
     
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  5. timwinters

    timwinters Touchdown! Greaser! PoA Supporter

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    Why in the world would you add flaps when trimming for best glide?
     
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  6. Clark1961

    Clark1961 Touchdown! Greaser!

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    Because your nickname is fanny?
     
  7. BigBadLou

    BigBadLou En-Route

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    Depends greatly on airplane and speed differential. A 172 might not see a big gain but try it in a faster airplane and you can easily gain 1,000' getting to Vg. And that might be the difference between making a rwy or landing out.

    I've done it before, just as a test. Try it out with your own airplane when you get a chance. It is a great exercise, it helps being prepared. And I like suggesting to be prepared. It increases your chances in a true emergency.
     
  8. FastEddieB

    FastEddieB Final Approach

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    I plan on doing that. May even take the GoPro along.
     
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  9. timwinters

    timwinters Touchdown! Greaser! PoA Supporter

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    Just as important...pull the prop to full coarse pitch. That's like getting kicked in the butt. It significantly reduces drag.
     
  10. BigBadLou

    BigBadLou En-Route

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    Just a minuscule detail people often overlook: if you lose your engine for real and are out of oil pressure, you are SOL with coarse prop pitch.
    But if you just lost, let's say, fuel supply or mags and your engine is still windmilling and building oil pressure, coarse pitch will work. :thumbsup:
     
  11. timwinters

    timwinters Touchdown! Greaser! PoA Supporter

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    true dat
     
  12. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Barring a problem specifically with the oil supply, will you have oil pressure whenever the prop is windmilling?
     
  13. FastEddieB

    FastEddieB Final Approach

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    Yes.
     
  14. brcase

    brcase Cleared for Takeoff

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    Obviously you wouldn't add flaps for best glide, but the point that most people recommending using the roll the trim back method forget to mention is you probably aren't going to land in that configuration. In fact if done well you should be either slipping or using flaps to get down to you chosen landing spot just because you planned it so there was no change of getting to low.

    My concern is I have seen pilots trained to just do this after a power outage and then they don't reconfigure when they setup for landing, which is where I see them get "scary slow".

    My analysis is that it works ok if you absolutely need best glide. But in most cases you are not going to need your best glide speed and your energy is better spent just making sure you don't stall, restarting the engine, or making as normal of a landing as possible. So it is kind of a neat trick to be aware of, but probably not the best procedure to use as a rote engine failure procedure.

    Brian
     
  15. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    For the planes I usually fly, best glide is at or just above normal final approach speed.
     
  16. Kritchlow

    Kritchlow Final Approach

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    I have no idea which way is mathematically better, but I’m betting the best way to do it is not to worry about it. We are likely talking 10 feet of glide here, but a mile if we get distracted with minutia.
     
  17. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I don't worry, I just do it the way I was taught.
     
  18. Kritchlow

    Kritchlow Final Approach

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    I never worried either By the time you realize what’s happening you’re almost there.

    It’s truly splitting hairs.
     
  19. Sinistar

    Sinistar Pre-takeoff checklist

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    So I have had two instructors. First one holds until best glide, the other pitches up - both quite adamant.

    This topic is like strapping a open face peanut butter sandwich to the back of a cat and dropping them. Who hits the ground?

    What about a plane with a excellent glide ratio (MD-80?) traveling pretty fast up at cruising altitude...do they pitch up?

    Also curious since they were fairly low, did Sullenberger pitch up right away or just hold altitude until their best glide?
     
  20. dmspilot

    dmspilot Pattern Altitude

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    Since they were climbing out I believe they were at or below best glide already.
     
  21. kgruber

    kgruber En-Route

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    I'm typed in several jets and never have seen a "best glide" speed published.
     
  22. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I've only had one instructor who taught me engine out procedure in a single, so I don't have that problem. And I've learned the hard way that if I'm going to deviate from what I was taught, I need a good reason.
     
  23. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Were they multiengine jets?
     
  24. Sinistar

    Sinistar Pre-takeoff checklist

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    But they surely have a glide ratio which must be somehow tied to a certain config (clean?) and pitch angle which I would think would then have a speed?
     
  25. dmspilot

    dmspilot Pattern Altitude

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    It would be a certain angle of attack.

    Aircraft with low parasite drag have high best glide speeds. I am pretty sure that the average passenger jet has a best glide speed somewhere in the 200s.
     
  26. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Do they publish best glide angle of attack for jets?
     
  27. coloradobluesky

    coloradobluesky En-Route

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    Some pilots seem to think that the longer they glide, the safer the off field landing will be. Thats possible, but its only one scenario. The tendency is to overshoot.

    I pull the power and glide on in, almost every landing. Makes every landing an "engine out" drill. Do it all the time, you get good at it.
     
  28. kgruber

    kgruber En-Route

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  29. Ravioli

    Ravioli En-Route PoA Supporter

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    Tim's right on this one. MT and others make electric adjustable props. So perhaps the only modification to his statement would be "if you can."
     
  30. mscard88

    mscard88 Touchdown! Greaser!

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    :eek: you take a happy pill today?
     
  31. Ravioli

    Ravioli En-Route PoA Supporter

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    Even a broken clock is correct twice a day.
     
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  32. danhagan

    danhagan Cleared for Takeoff

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  33. BigBadLou

    BigBadLou En-Route

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    ROP or LOP? ;)

    [flame suit on]
     
  34. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    High wing or low wing?
     
  35. mscard88

    mscard88 Touchdown! Greaser!

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    Neither.

    [​IMG]
     
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  36. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Winner!

    (But don't you mean "both"?)
     
  37. Kritchlow

    Kritchlow Final Approach

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    I have. The citations have a chart.
    Not sure if Airbus actually publishes a speed, but you can fly “green dot”. Green dot is a marker on the airspeed tape depicting L/D max.
     
  38. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    You get a tiny bit of extra drag with the higher AoA initiating the climb, but only for a second or less... And then the lower speed makes up for it.

    This.

    Speak for yourself. The Mooney has a 50-70 knot difference (depending on altitude) between cruise and best glide.
     
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  39. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Even a 172 has a 45 - 55 knot difference, depending on the horsepower.
     
  40. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Best glide in a 172 is 79 KIAS, isn't it? I've never seen a 134-knot 172! :eek: