RCU Forums - Spoilerons

Let's say you have your end point up aileron travel limit set at 20 mm. 75% of that would be 15mm. So, when you hit the switch for full spoileron deployment, 100% spoileron, the aileron should move up 15 mm.

Do your testing of these settings at 100 feet or higher in case you get strange behavior. I have seen people set up flaps, flaperons, spoilers and spoilerons then test them near the ground and wreck their plane.

You test high till you get the behavior you want. THEN you test near the ground.

This is especially true as you dial in your elevator comp setting for each spoileron setting. The only glider I have ever used spoilerons on was my Easy Glider and that needed down compensation, not up.

With full spoilerons deployed you want the glider to maintain a level or slightly nose down attitude, not go into a dive or balloon up. Same with setting up flaps. The goal is to reduce the glide ratio, not do dive the glider or stall it.

You might find this helpful:

GLIDE PATH CONTROLS

by Ed Anderson

Both power
planes and gliders can incorporate glide path controls to add to the options a
pilot has when flying his plane. We have all seen commercial airliners dropping
flaps during landings. Likewise gliders, which are flown without the use of a
motor, also benefit from glide path controls though they may be used in slightly
different ways on a glider in order to gain the best control during flight and
during landing. While a power plane has the option to “go around” if the
approach is not good, when a glider comes in to land, it is going to land.
Without a motor there is no going around. And gliders are often flown in
thermals where the lift can become so strong we may feel we need help to get
them out of the lift. That is why we may choose to incorporate glide path
controls into our aircraft.

For the rest of
the discussion I will focus on the controls and their use in the context of
gliders as this takes the effect and option of raising or lowering power out of
the discussion and focuses on the controls themselves. Even on gliders, these
glide path controls are not absolutely necessary as many glider pilots fly
without the use of glide path controls, but they can be helpful. Hopefully this
will clarify the terms and the use of these controls.

First, lets make sure we are using the same terms.

Spoilers and Spoilerons

Spoilers sit on top of the wing, typically near the spar. This is how the
Mystique RES is designed, for example.

Spoilers will reduce lift while inducing drag, but their primary value is
not as brakes but as lift reducers. This raises the stall speed, the speed at
which the wing can no longer produce enough lift to support the aircraft. So
the wing will stall at a higher speed. Some rise like barn doors. This is what
we typically call spoilers. Some come straight up like a blade. These we often
call air brakes.

When spoilers are deployed typically the nose will drop, due to reduced
lift, and we compensate with some up elevator to keep the glider from going into
a dive. The best effect is that the glider remains fairly flat but the sink
rate is raised so it comes down more quickly but without gaining a lot of
speed.

Spoilerons are trailing edge devices that go up. This might be based on
ailerons, full span ailerons, flaps or flaps and ailerons in combination.
Spoilerons will reduce camber, reducing lift. Think of this as raising the
trailing edge like an aileron but on both sides at once.
The wind hits the raised trailing edge and induces a pressure down at the
trailing edge of the wing. Whether you think of it as induced down force or
reduction of lift the effect is the same. When done on both wings at the same
time this often induces a rise in angle of attack, it picks up the nose since
the down force is behind the CG. This may require some down elevator
compensation to keep the glider from stalling.

Spoilerons induce drag as you raise them but their primary purpose is not
as brakes. This also raises stall speed meaning the wing will stall at a higher
speed. So spoilers and spoilerons are different but their overall purpose for
use is he same. The elevator compensation needed may be opposite.

Flaps and Flapperons

Flaps go down and increase the wing’s camber, makes the wing bottom more
concave. This causes more drag and more lift while reducing stall speed
allowing the plane to fly more slowly without stalling. That is why they help
fast planes land more slowly. What we are looking for is not the breaking
effect of the drag as much as it is the lowering of the stall speed which allows
the plane to land more slowly. When flaps are deployed the increased lift will
typically bring the nose up so we compensate with down elevator to avoid
stalling.

Flaps might be set to as much as 90 degree down angle. However 60 degrees
is typically all you need for enhanced, slower landing speed.
If you have a glider with ailerons you can use them as flapperons. This
works best when the ailerons are full span, like many discus launched gliders.
Here you get full trailing edge control with only one control surface on each
wing. You get thermal camber (trailing edge slightly down) and reflex
(trailing edge slightly up) and you get flap behavior and spoileron (not
spoiler) behavior if you can get enough upward motion. This works best on a
straight wing where any dihedral is at the root rather than a curved wing or a
polyhedral wing where dihedral is introduce gradually over the length of the
wing.

Brakes

All of these controls induce increased drag at sufficiently high angles of
deflection, so they can be used as brakes to either slow the aircraft down or to
prevent it from gaining speed. For example, imagine you are flying in a thermal
duration contest. You are in a thermal, are quite high and want to get down
fast so you can land at the exact time that will get you the best score. You
can extend your flaps or spoilers and push the nose over to go into a dive to
lose altitude quickly. Both will add drag which will reduce the amount of
speed you will gain in the dive. In my experience with RC gliders this works
better with flaps as flaps are usually larger than spoilers but it works for
spoiler too.

Likewise you can use these controls as you come near to whatever you
intended landing spot may be to dump energy and cut the glide short. Going to
90 degree flaps or 90 degree spoilers will induce drag to dump energy, but
again, because flaps tend to be larger they do a better job of this.

Spoilers do add the ability to “pin” the plane to the ground on landing.
Because they reduce lift, if you deploy spoilers on landing the wing will have
reduce lift and therefore the plane will have less of a tendency to rise off the
ground or hop as you land near the stall speed of the airplane or glider,
especially in gusty landing conditions. The next time you ride that big
airliner watch the wings on landing. Once they touch, many will raise spoilers
or airbrakes to help slow the plane and reduce the lift of the wing so the plane
has less chance of going back into the air.

Versatility

In my opinion, flaps are more versatile than spoilers as you can use them
to lower stall speed or increase it. However flaps are also more
dangerous.

If you lower flaps, reducing the stall speed you can slow the plane down
and keep flying below the normal stall speed. If you pull the flaps in because
you realize you are not going to make the field you MAY stall because as you
pull the flaps in the stall speed goes back up. If you are flying too slowly
the plane will drop like a rock.

Spoilers on the other hand are more forgiving. If you apply spoilers too
soon and realize you want to extend the glide you can retract the spoilers which
lowers the stall speed. You will not stall and you will not drop out of the sky.
The glide is extended. Personally I prefer spoilers for new pilots for this
reason. Gliders with R/E and spoilers are called RES gliders.

Each approach has advantages. Flaps more versatile but more prone to error.
Spoilers are less versatile but more forgiving of errors.
If I was modifying the trailing edge, I would make them flaps rather than
spoilerons. However if I was a new glider pilot and wanted to avoid those
stalling errors, I would install spoilers, not spoilerons.

I learned to fly gliders on a RES glider, a Great Planes Spirit. I fly RE,
RES, REA and full house REAF gliders and I enjoy them all. But you fly them all
a little differently. The more controls, the more versatile and the greater
propensity for mistakes.
Of course, your smileage will vary.