What are the advantages and disadvantages of spoilers vs. ailerons for roll control?
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.Originally Posted by dougbush
Last edited by martymayes; 06-03-2013 at 07:23 AM.
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?]
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
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 “I drink and know things” Stovall
PP ASEL - IA
RV-10 N728TT - Flying
EAA Lifetime Member
WAR DAMN EAGLE!
Not a smart guy so I'll say ailerons, hands down.
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
Speaking from my experience flying a Starflight Ultralight (think Quicksilver but different and I think better construction). The spoilers on the Starflight give reasonable roll control but consider that I always remain upright. I am not at all sure that spoilers would work inverted and suggest that before you try anything of that nature that you build a RC model to test out the idea. Now the Starflight flys like an early Cub or Aeronca but I am 99% sure the reason they used spoilers in the design is that they create very little twisting force on the wing letting the structure be lighter.
Good discussion,
The B52 is spoilers only..limited to 45 degrees of bank I believe. Most airliners have both. T38 was aileron only with a 720deg/sec roll rate. The F4 had both. The C&D and hard wing E had serious adverse yaw issues at high AOA...the down aileron would just increase drag and pull the jet out of control.
At low AOA the aileron rules in roll, high AOA, the spoiler works better. (or rudder in the F4's case). An AOA or flap lever derived lockout for ailerons? The DC10 and 767 have a second aileron that works at lower speeds. Flap position or airspeed is used lock/unlock the extra aileron in those if I remember correctly.
Not an aero engineer but I did teach high school Physics 20 years ago.
Jake
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