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Thread: Spoilers vs. Ailerons for roll control?

  1. #1

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    Spoilers vs. Ailerons for roll control?

    What are the advantages and disadvantages of spoilers vs. ailerons for roll control?

  2. #2

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    Quote Originally Posted by dougbush View Post
    What are the advantages and disadvantages of spoilers vs. ailerons for roll control?
    While there are probably many, #1 advantage would have to be eliminating undesirable yaw caused by ailerons.
    Last edited by martymayes; 06-03-2013 at 07:23 AM.

  3. #3
    Mike Switzer's Avatar
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    I have been seriously considering spoilers for my design because if properly executed they will have less drag (no aileron gap). I'm still trying to figure out how to add trim back in without adding drag.

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    Quote Originally Posted by Mike Switzer View Post
    I have been seriously considering spoilers for my design because if properly executed they will have less drag (no aileron gap). I'm still trying to figure out how to add trim back in without adding drag.
    You can always use both. Smaller size/range of travel ailerons augmented with spoilers. Get the best (and worst) of both worlds. [Who says this design stuff is supposed to be easy anyway?]

  5. #5

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    Some thoughts...

    The big disadvantage to spoilers is the total lack of control feel that pilots expect. For light aircraft that use spoilers such as the Helio, you will see that there are still small ailerons to contribute to control and to feedback to the pilot. The aileron allows more precise control inputs.

    Normally the yoke or stick force varies with speed and deflection of the control surface. Spoilers do not provide this force feedback.

    More complex airplanes employ artificial feedback so that the stick forces match the desired and conventional relationship between pitch, roll, and yaw.

    In addition, getting spoiler extension to result in the expected linear response to pilot control input through a mechanical linkage is a tricky bit of design. Spoilers operate through the wing's boundary layer which changes in depth with speed and angle of attack. Can require multiple test and modify iterations of multiple parts. A mechanical linkage that is not aided by a flight data computer can likely only be set up to operate well in a specified set of conditions.

    Ailerons add lift to one wing and reduce lift and add drag to another. Off the cuff, I think that allows the overall lift of the wing to be higher than if a spoiler is only applied to one wing to cause the roll by killing lift on that wing without creating lift elsewhere.

    If you have both spoilers and ailerons you buy two sets of linkages, which means moire build time, more weight, more test time, more maintenance.

    Looking around the GA fleet, I will hazard a guess that if spoilers delivered superior performance across the entire flight envelope, they would be much more common than they are.

    Best of luck,

    Wes
    N78PS

  6. #6
    Auburntsts's Avatar
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    For the smart guys in the crowd, for a given span which configuration will produce the greatest roll rate or is it a wash?
    Todd Stovall
    Aka tsts4 on POA & Matronics, and Auburntsts on VAF, RV Airspace, AOPA, & Purple Pilots
    PP ASEL
    Building an RV-10 N728TT
    My builder's log (which is woefully out of date): www.mykitlog.com/auburntsts
    WAR DAMN EAGLE!

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    Some decades ago, I was sharing a room in a Navy hospital with a room mate who was a USAF Col. He had a little experience with the P-61 Black Widow. It had smallish ailerons linked to roll spoilers. The spoilers came into play after a certain amount of roll input. He told me that although the P-61 was as big as some bombers, it rolled like a fighter. It could do a decent job against many single engine fighters.
    Two of my fellow pilots where I use to work flew Mitsubishi MU-2s. They said that it had high wing loading so it that it could go fast. They had to design full span flaps so that it had reasonably slow landing characteristics. So that meant spoilers for roll. I was told that it seemed to roll about the outboard wing tip rather than the longitudinal axis. If you can imagine something like that. They both liked the plane.

    Both of these airplanes likely provided a good living for engineers and test pilots as they tweeked the designs.

    Bob

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    Quote Originally Posted by Auburntsts View Post
    For the smart guys in the crowd, for a given span which configuration will produce the greatest roll rate or is it a wash?
    Not a smart guy so I'll say ailerons, hands down.

  9. #9
    Mike Switzer's Avatar
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    I was thinking of an arrangement with spoilers on both the top & bottom of the wing springloaded enough to hold them shut, operated by a rotating shaft with arms that would either push the top or bottom spoiler open - that way you would still have control feel. If you use the right kind of hinges there shouldn't be anything exposed to mess up the wing profile.

  10. #10
    Mike Switzer's Avatar
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    Aren't there several of the more popular gliders that use spoilers?

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