"Stick and Rudder Moments" - redux

Discussion in 'Hangar Talk' started by FastEddieB, Feb 21, 2015.

  1. FastEddieB

    FastEddieB Final Approach

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    In another thread a pilot opined that wind made a difference in cooling in a Seneca. I searched every which way and cannot find my original post on "Stick and Rudder Moments". So, I thought I would amend it (example #5) with the current example and re-post it:


    As background, Stick and Rudder is a book written by Wolfgang Langewiesche in 1944. Though a little dated, it still makes good on what the subtitle promises: “An Explanation of the Art of Flying”.

    [​IMG]


    Much time is spent in the book describing what makes flying so different and challenging compared to ground based activities.

    We spend most of our lives anchored to the ground in one way or another. In fact, to say someone is “well grounded” or that he or she “has their feet on the ground”, is generally considered a compliment.

    But all that time spent on the surface may make it difficult to shift gears when the wheels of a plane leave the ground. It takes a while to adjust and to understand, and even experienced pilots can slip up from time to time.

    It has to do with frames of reference. One is the ground. We think of it as stationary, but standing on the surface of the planet you may be moving up to about 1,000 mph, depending on your latitude. But if you know how to juggle, you don’t have to factor in the speed at which you’re moving - relative to the surface you’re stationary, and that’s all that matters. Similarly, if you’re juggling on a moving train - since your frame of reference is now the train, no allowance for its movement need be made.

    The essence is that, once in the air, the plane has zero reference to the ground as far as flight characteristics go. Your frame of reference now becomes the air mass in which you are moving. The implication is that a steady wind has no effect on the plane, other than its path over the ground. The plane is simply flying in an air mass which is itself moving. Disregarding gusts and shear, once a plane is in the air, like a free balloon, there is no wind.

    I wish to clarify what I mean when I call something a “Stick and Rudder Moment”. A pilot will do or say something where a lightbulb goes off in my head and I suspect they may not be adequately making the transition from ground-based to flight-based thinking. The upside is that it can often become a "teachable moment".


    Here are some examples I’ve come across, and I’m sure you guys can come up with many more.

    1) The “Dreaded Downwind Turn”.

    This is the grandaddy of "Stick and Rudder Moments". Many pilots believe that the turn from crosswind to downwind is especially dangerous. Why? The plane may stall as it is picking up a tailwind during the turn, putting it closer to the stall.

    Such is not the case. If planes do tend to stall there, it is due to the illusion of increased speed leading them to slow down too much or not realize speed is decaying. There is no “wind” pushing against the rear of the plane, causing it to stall.

    2) A fellow on the Cirrus Owner’s site observed that a quartering tailwind seemed to push his plane ahead by more than the wind velocity. For example, he’d be flying along with a TAS of 190k and a quartering tailwind of 10k and find his groundspeed being greater than the combination of 190+10. He figured it was like a sailboat “tacking”, and that some sort of trigonometry was letting the quartering tailwind “squeeze” his plane forward faster than the wind velocity.

    The thread (“Winds?”) went on for hundreds of posts with other pilots and instructors trying every imaginable explanation and analogy to show him the error of his reasoning. I don’t know if we ever did, and the same theme was continued in another thread by the same fellow. But it was a fun, if somewhat aggravating ride.

    3) Flying a demo Cirrus northbound in FL, I noticed on autopilot it was flying slightly right wing down. I mentioned it to the demo pilot, who opined that it was probably just the autopilot correcting for the right crosswind.

    4) A pilot posted that when he approached in a crab with a crosswind from a certain direction, he could feel it in his prop.

    5) I’ve heard it said cowl flaps are especially useful when flying downwind, when cooling would otherwise be compromised by the tailwind. More recently, a forum poster here thought winds affected cooling in a Seneca, possibly due to cowling shape. Then he doubled down with: "On my 206 I've notice a 5-10 degree change in CHT based on a strong wind. I am not a fluid dynamics expert, so I have no idea exactly why. Perhaps a slight pressure change in the cowl as I mentioned, or slight turbulence in the relative wind, IDK."

    6) Someone suggested in a strong enough wind, a plane that was not tied down could eventually just hover.

    7) Many have expressed that banking the airplane may cause fuel to flow unevenly from wing tanks. When queried, they were not referring to uncoordinated flight.

    8) And, of course, there was the suggestion to use an iPad app’s speed readout as an aid when landing.



    One thought exercise is to imagine that you’re flying a plane capable of 50k slow flight in a 50k wind. Start directly into the wind with a zero groundspeed. Then start doing 360’s. With each 360 your groundspeed goes from zero to 100k and back to zero. Imagine how that will feel as you speed up to 100k only to slow back down to zero. How will that feel? How will that sound? You surely will be able to tell when you’re upwind and when you’re downwind, right? The answer is so nonintuitive that you might not believe it, but its true. Try it some time under the hood and the answer will be clear - though not what you might think.

    Anyway, let me open the floor to discussions of any of the above, or feel free to add your own “Stick and Rudder Moments".
     
    Last edited: Feb 21, 2015
  2. G-Man

    G-Man Line Up and Wait

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    Really enjoyed reading this. Quite a thought-provoker over morning coffee.

    I love the exercise of doing slow 360s in a strong steady wind. That should really teach a lot. Thanks for sharing your comments.
     
  3. Mason

    Mason Pattern Altitude

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    The airplane doesn't know or care one whit about a steady wind. It is totally unconscious of the wind.
     
  4. FastEddieB

    FastEddieB Final Approach

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    Yep!

    Kind of the whole point of the post, really.
     
  5. SixPapaCharlie

    SixPapaCharlie May the force be with you

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    Then how come the plane weather-vanes when you lift off in a crosswind?

    :popcorn::popcorn::popcorn:
     
  6. RotorDude

    RotorDude Pattern Altitude

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    That's only if you have one wheel still on the ground, in which case the plane becomes a(n expensive) windsock. :)
    After it's in the air, it doesn't care.
     
  7. FastEddieB

    FastEddieB Final Approach

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    Shows how subtle effects can be missed.

    I still hold that as soon as the last tire leaves the surface, the entire plane will simply move laterally with the air mass, and not "weathervane". It's definitely my experience. Lots of pilots hold that it will, but I think it's because they are so used to crabbing into the wind after takeoff that it seems to happen on its own.

    I posted my little experiment before. Here it is again:

    http://youtu.be/NhCFAJybVyw

    I could detect zero tendency for the model to "weathervane"' and that leaf blower was really honkin'!
     
  8. whifferdill

    whifferdill Line Up and Wait

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    +1. But nothing in aviation seems more controversial than crabs, slips, skids, and x-winds. :D
     
  9. SixPapaCharlie

    SixPapaCharlie May the force be with you

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    I know, I just felt like doing a little trolling this morning.
    Also you cannot do any of the things Whifferdill said with flaps extended beyond 10 degrees or you will enter a flat spin and die.
     
  10. jsstevens

    jsstevens En-Route

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    Or have to pull the chute, in your case. It's probably cheaper to die...
     
  11. narchee

    narchee Line Up and Wait

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    Wind speed and direction is all relative the ground. Once you're airborne it is completely irrelevant other than it affects your GS and how long it will take you to get to your destination. That is the only effect. But you all know that. :lol: If you claim otherwise you're either trolling or...well I won't say.
     
  12. Howard Wilson

    Howard Wilson Pre-takeoff checklist

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    Two words: wind shear:eek:
     
  13. overdrive148

    overdrive148 En-Route

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    +1 for science!
     
  14. Van Johnston

    Van Johnston Line Up and Wait

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    "3) Flying a demo Cirrus northbound in FL, I noticed on autopilot it was flying slightly right wing down. I mentioned it to the demo pilot, who opined that it was probably just the autopilot correcting for the right crosswind."

    Help me with this one. If the autopilot is flying a heading, I see your point. But if it is coupled to a VOR or localizer or GPS and trying to fly a ground track, isn't flying wing low into a crosswind what it would do?
     
  15. narchee

    narchee Line Up and Wait

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    More likely the guy on the right side was fatter :lol:
     
  16. Clark1961

    Clark1961 Touchdown! Greaser!

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    Flying wing low is what the autopilot will do when the aircraft is out of rudder trim.
     
  17. FastEddieB

    FastEddieB Final Approach

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    No.

    It may make tiny corrections to the right to establish the WCA, but once established, should fly straight and level, ball in the center. If a wing was down and the plane not turning, it's flying along in a slip, which is never desireable enroute.

    The demo plane was, in fact, slightly out of rig.
     
    whereisrandall likes this.
  18. Van Johnston

    Van Johnston Line Up and Wait

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    Ok, thanks.
     
  19. Stewartb

    Stewartb En-Route

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    I love the downwind turn topic. It separates the theoretical pilots from the real ones.
     
  20. FastEddieB

    FastEddieB Final Approach

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    As an aside,I stumbled upon "Stick and Rudder" from an entry in "The Whole Earth Catalog", probably around 1970.

    I still have that "Whole Earth Catalog", and here's the entry that got me hooked on flying:

    [​IMG]

    This certainly dates me, but I wonder if anyone else remembers this entry?
     
  21. txflyer

    txflyer En-Route

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    Fly it like you STOL it ♦
    Stick and Rudder got tedious and redundant to read, but I stuck with it. It is good knowledge.

    There's a grey area when taking off and landing a TD with a crosswind where it will weather vane if you don't have enough rudder in there. It's usually right when the tail comes up on take off, or right before it starts to fall on landing after doing a wheelie.

    Beware the grey area! :hairraise:
     
  22. Hank S

    Hank S En-Route

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    If your wheels are on the ground, you aren't flying yet, and ground track is controlled at least partially determined by steering the wheels.
     
  23. Flavius Renatus

    Flavius Renatus Pre-takeoff checklist

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    I try and read this book once a year as a reminder that controlling your AOA is the single most important thing to pay attention to.

    Flav
     
  24. txflyer

    txflyer En-Route

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    Fly it like you STOL it ♦

    [​IMG]


    I had one of these installed and haven't looked back since.

    Now watch me get called all kinds of names .... :lol:
     
  25. denverpilot

    denverpilot Taxi to Parking

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    That looks like right after takeoff, the airplane will crash! ;) ;) ;)
     
  26. jimhorner

    jimhorner Pre-takeoff checklist

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    Enjoyable read. Reminds me of the time I had a conversation with a non-pilot about wind effects. Smart guy, Masters in mechanical engineering, but he just couldn't grasp the fact that, in a steady, non-turbulent flow (no wind shear, etc.) airspeed is completely independent of wind speed and direction. He actually thought that an airplane would fall out of the air in a headwind above a certain speed...

    Completely right, but flying one wing low in UN-coordinated flight can be useful at times. One time I was flying a Decathlon cross-country, and the right wing had more gas than the left because the plane had been parked on a slope with the left wing high. Since the tanks are interconnected, I flew along for a while with the left wing down and full right rudder. Seemed to equalize the fuel in the tanks after a bit.
     
  27. asechrest

    asechrest En-Route

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    Sure. But what if the 50k slow flight 360s were on a treadmill for the downwind-facing 90 degrees of the circle? The key to the answer is understanding the difference between a forward slip and a regular slip. :goofy:

    --

    Anyway, I enjoyed the post a lot. Thanks for sharing. Your comments about the Earth really brought this home for me as far as solidifying my ability to intuitively ingrain some of this, rather than to just know (but not "feel") that it is true. To whit: I'm on the surface of the Earth whipping along as it turns, yet I feel no different if I walk in the direction of the Earth's turn vs. the opposite.

    Next time I make a trip to Deep Creek in NC, I'm going to hop out of my tube, close my eyes, and swim against the current, then reverse and do the same in the opposite direction. How will I feel?
     
  28. FastEddieB

    FastEddieB Final Approach

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    Apparently Flight Design CT's often have trouble getting even fuel flow.

    Some of the pilots routinely lower a wing into a slight slip to help balance the fuel between the two wing tanks.
     
  29. FastEddieB

    FastEddieB Final Approach

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    Cold???
     
  30. asechrest

    asechrest En-Route

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    Happy, mostly. Love that place. :)
     
  31. Steve Job

    Steve Job Pre-takeoff checklist

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    I have that same model, but I put mine on top of the glareshield. It isn't pretty up there, but I'm not sure I would pay as close attention to it as I should when I'm low and slow (and looking out the window). How's that placement working out for you?
     
  32. FastEddieB

    FastEddieB Final Approach

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    Over on another forum, a fellow is totally enamored with his CT.

    Marvels at how well the autopilot keeps the ball in the center...

    ...in spite of the fact its not connected to the rudder!

    But more on point and worthy to be added as #9, the only time he has to help the trim is when it wants the nose held down due to strong headwinds!
     
    Last edited: Mar 21, 2015
  33. FastEddieB

    FastEddieB Final Approach

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    Cross-posted from a thread about a Cirrus fatal:

    This may seem like a trivial point, but sometimes word choice can help point out where there might be errors in properly visualizing what's going on with a plane in flight.

    Both "blown" and "pushed" conjure up an image of a force, like a giant hand, acting upon the plane. That somehow more pressure is being exerted on one side of the plane plane by the wind. Or that a wind "blowing" from the rear can render the elevator less effective, which started us down this rabbit hole.

    Better and more accurate to say a given wind causes an airplane in flight to drift, as the airmass in which it is flying is itself moving. No "pushing" or "blowing" involved.
     
  34. Cooter

    Cooter Pattern Altitude

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    Wind doesn't "blow"? It seems you want to take your point a little too far.
     
  35. Sundancer

    Sundancer Pattern Altitude

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    That's scary, and a touch sad, too. . .
     
  36. FastEddieB

    FastEddieB Final Approach

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    Not against an airplane in flight.

    Gusts and shear excepted.
     
  37. Cooter

    Cooter Pattern Altitude

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    Excepting gusts and shears is like talking about surfing and excepting the waves. But even so, you are pressing too hard to make your point. The concept of being blown by the wind does apply when the ground is a reference. So when speaking of landing or patterns or takeoffs, you shouldn't rule it out in order to maintain consistency with your point. There is a sense in which the elevator is less effective and your flight control inputs change because of the influence of winds. I think your point would be better made by maintaining the distinction rather than erasing it.
     
  38. BigBadLou

    BigBadLou En-Route

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    Oh man, this thread can only get good! :D
    :popcorn:
    (I am an engineer - a real one - so I love physics and only laugh at those who bastardize it to suite their misunderstanding :) )
     
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  39. BigBadLou

    BigBadLou En-Route

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    I'll call you a name: "NON-Navy pilot". :)
    If you were truly a Navy flyboy, you'd have installed the meatball. Boooooo! :-D

    Just giving you hard time. How long have you had it? Do you find yourself paying still a lot of attention to it as you did on the first few test flights? Do you notice anything you hadn't before? Does it change your flying characteristics?
    Sorry for all the questions. It might not be a bad idea for you to start a separate thread to discuss your findings.
     
  40. FastEddieB

    FastEddieB Final Approach

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    Disagree. Sometimes we have to remove distractors to focus on general principles.

    Fine. My point was not that one can never say a plane is "blown" or "pushed" by the wind. I've undoubtedly used that language myself. My point was that, in my experience, use of that language can sometimes alert an instructor to a basic misunderstanding of the forces acting on a plane in flight. I think the majority of the misconceptions listed in the OP can be traced to thinking that, even once in the air, wind still blows against a plane.

    I still think that's confusing. Of course one's flight control inputs change depending on wind, if one is talking maneuvering with reference to the ground. I've spent many hours teaching ground reference maneuvers to teach that specific skill. But if one holds that the elevator is less effective in a tailwind, I think that's a reach, or at least open to easy misinterpretation.
     
    Last edited: Jun 21, 2016