Full-span flaperons as airbrakes?

Bruce,

Your Kestrel seems to have a different setup from mine. I have a
Series 1 bird, so maybe Slingsby changed the layout with later models?
Tow release is under the left inner thigh, rudder pedal adjustment is
under the right inner thigh. Drogue deploy is on the left cockpit
sidewall above the air vent, just in front of the panel; drogue
jettison is in the centre pedestal of the panel to the right of the
landing flap handle (with the nose vent control pull-knob between
them).
For me, it's a quick movement of the hand from the spoiler lever
forward to the drogue deploy; the drogue jettison is a bit further
since I have to reach the panel just to the right of my stick.
My spoliers only add 1 kt of sink, so I have to judge my location and
height for when to put on full flap. I like the comment in my POH
(sorry, can't quote it just now) about the spoilers being ineffective.

To try and keep on point here, LS-6, LS-10, LS-3, PIK 20 D, Ventus C,
ASW-17 come to mind as having full span flaperons. The entire
trailing edge moves the same amount when moved as flap or aileron.
ASW-20, PIK 20B, Zuni, SGS 1-35, HP Series, 301 Libelle, Diamants,
Ventus A/B, Kestrel, etc do NOT have full span flaperons. They have
flaps and ailerons, and varying degrees of interconnection between the
two.

Only plane I know of that had a full span flap that was used at large
deflections (greater than 30 degrees) was the HP-17. Notice, it did
not have full span flaperons. It had spoilers for roll control. And
I understand the contestants had a great time watching Schreder take
off with it, as he went from tip to tip, side to side on the runway
until he finally got the plane into the air. This was likely due to
the fact that you could only reduce the lift a bit on the high wing
and add drag to it to try and pick up the down wing.

Full span, large deflection flaperons will likely provide very poor
roll control at any deflection beyond about 30-45 degrees, as the flap
will be likely be stalled, and the main thing you will get is
differential drag or a yawing moment when you moved the stick to try
and roll the plane. Oh, and I don't consider the Ventus A/B, Mini
Nimbus, or Mosquito to have drag flaps. They have cruise flaps and
trailing edge air brakes. Drag flaps have you looking out the top of
the canopy at where you are going to land when you put them full on.
You are still looking out the front of the canopy at where you are
going to land with trailing edge air brakes.

The ASW-20 was the first to get the ailerons back up as the flaps went
on down, getting the plane into what a previous poster said is called
"crow mode" in the model world. I think the biggest thing it does is
makes it so the ailerons won't stall once you are on the ground in two
point, tail low attitude. I don't think it was done for added drag or
improved in flight handling. You already get ENORMOUS geometric twist
when your inboard flap is down 50 degrees and your ailerons are still
down 8. However, these flapped ships like to have the ailerons up
when sitting two point on the ground in order to have aileron
authority, and Schleicher got this (among so many other things) right
by putting them back up so you can leave the flaps all the way down
after you land. That way, your left hand doesn't have to keep jumping
around in the cockpit grabbing different handles. Set the flaps, use
the dive brakes and land. No more needed hand changes.

Steve Leonard

Steve Leonard wrote:
To try and keep on point here, LS-6, LS-10, LS-3, PIK 20 D, Ventus C,
ASW-17 come to mind as having full span flaperons. The entire
trailing edge moves the same amount when moved as flap or aileron.
ASW-20, PIK 20B, Zuni, SGS 1-35, HP Series, 301 Libelle, Diamants,
Ventus A/B, Kestrel, etc do NOT have full span flaperons. They have
flaps and ailerons, and varying degrees of interconnection between the
two.

Only plane I know of that had a full span flap that was used at large
deflections (greater than 30 degrees) was the HP-17. Notice, it did
not have full span flaperons. It had spoilers for roll control. And
I understand the contestants had a great time watching Schreder take
off with it, as he went from tip to tip, side to side on the runway
until he finally got the plane into the air. This was likely due to
the fact that you could only reduce the lift a bit on the high wing
and add drag to it to try and pick up the down wing.

Full span, large deflection flaperons will likely provide very poor
roll control at any deflection beyond about 30-45 degrees, as the flap
will be likely be stalled, and the main thing you will get is
differential drag or a yawing moment when you moved the stick to try
and roll the plane. Oh, and I don't consider the Ventus A/B, Mini
Nimbus, or Mosquito to have drag flaps. They have cruise flaps and
trailing edge air brakes. Drag flaps have you looking out the top of
the canopy at where you are going to land when you put them full on.
You are still looking out the front of the canopy at where you are
going to land with trailing edge air brakes.

The ASW-20 was the first to get the ailerons back up as the flaps went
on down, getting the plane into what a previous poster said is called
"crow mode" in the model world. I think the biggest thing it does is
makes it so the ailerons won't stall once you are on the ground in two
point, tail low attitude. I don't think it was done for added drag or
improved in flight handling. You already get ENORMOUS geometric twist
when your inboard flap is down 50 degrees and your ailerons are still
down 8. However, these flapped ships like to have the ailerons up
when sitting two point on the ground in order to have aileron
authority, and Schleicher got this (among so many other things) right
by putting them back up so you can leave the flaps all the way down
after you land. That way, your left hand doesn't have to keep jumping
around in the cockpit grabbing different handles. Set the flaps, use
the dive brakes and land. No more needed hand changes.

Steve Leonard

And unfortunately Schleicher patented the mixer - so one of the more
effective safety innovations has not been widely used.

Relying on a manual process as per T59D is a busy solution and error
prone. So it looks like the industry went to more powerful airbrakes and
dump the flaps on the ground run.

Pity really.

--- news://freenews.netfront.net/ - complaints: ---

Bruce wrote:

The ASW-20 was the first to get the ailerons back up as the flaps went
on down, getting the plane into what a previous poster said is called
"crow mode" in the model world. I think the biggest thing it does is
makes it so the ailerons won't stall once you are on the ground in two
point, tail low attitude. I don't think it was done for added drag or
improved in flight handling. You already get ENORMOUS geometric twist
when your inboard flap is down 50 degrees and your ailerons are still
down 8. However, these flapped ships like to have the ailerons up
when sitting two point on the ground in order to have aileron
authority, and Schleicher got this (among so many other things) right
by putting them back up so you can leave the flaps all the way down
after you land. That way, your left hand doesn't have to keep jumping
around in the cockpit grabbing different handles. Set the flaps, use
the dive brakes and land. No more needed hand changes.

Steve Leonard

And unfortunately Schleicher patented the mixer - so one of the more
effective safety innovations has not been widely used.
About 15 years ago, Gerhard Waibel told me they purposely did not patent
their system. They thought it was such an important safety feature it
should be available to the other manufacturers; to Schleicher's surprise
and dismay, none had ever used it, even though it was introduced on the
ASW 20 in about 1975.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

On Mar 9, 12:59*am, Eric Greenwell wrote:
Bruce wrote:

The ASW-20 was the first to get the ailerons back up as the flaps went
on down, getting the plane into what a previous poster said is called
"crow mode" in the model world. *I think the biggest thing it does is
makes it so the ailerons won't stall once you are on the ground in two
point, tail low attitude. *I don't think it was done for added drag or
improved in flight handling. *You already get ENORMOUS geometric twist
when your inboard flap is down 50 degrees and your ailerons are still
down 8. *However, these flapped ships like to have the ailerons up
when sitting two point on the ground in order to have aileron
authority, and Schleicher got this (among so many other things) right
by putting them back up so you can leave the flaps all the way down
after you land. *That way, your left hand doesn't have to keep jumping
around in the cockpit grabbing different handles. *Set the flaps, use
the dive brakes and land. *No more needed hand changes.

Steve Leonard

And unfortunately Schleicher patented the mixer - so one of the more
effective safety innovations has not been widely used.

About 15 years ago, Gerhard Waibel told me they purposely did not patent
their system. They thought it was such an important safety feature it
should be available to the other manufacturers; to Schleicher's surprise
and dismay, none had ever used it, even though it was introduced on the
ASW 20 in about 1975.

Good to know that I didn't violate any patents. Years ago I installed
this feature on the RS-15 I owned. Actually, any HP series glider
with a flap/aileron interconnect can easily be set up to have this
behavior and I believe that many/most are. One needs only to modify
the cam slot in a piece of 3/16" aluminum plate. The guy to whom I
sold the RS wanted the ailerons to go "crow" at smaller flap
deflections. He was able to easily change it himself. In general, it
makes a huge difference in maintaining control during landing rollout
as described and the best part is crow mode happens automatically.
Just set the flaps and land. Dive brakes/spoilers? What are
those? ;-)

Regards,

-Doug

Thanks for all the good discussion.

I don't understand why flow separation above a full-span flaperon
would cause you to lose aileron control everywhere in the speed
braking region. Let's say you're at 45 degrees flap, and the flow has
separated on top, but you'd have plenty of pressure on them below. So
I'd guess the force on the control surface might be at 45 degrees or
so above horizontal. It seems you would still have some good aileron
control because raising or lowering opposite-side flaperons would
still change that force a lot, with its vertical component. It seems
the bigger problem might be yawing effects that would come with it?

Bret,

Model gliders have tried most of these control ideas at least once in
the past 20 years. It's much easier with the servos and computer
controlled radios to get almost any mixing arrangements you can think
of.

In the case of the full-span flaperon: Once the flap function exceeds
about 25 degrees down, the additional downward deflection of the
aileron function does NOT create much lift to make a roll, in fact it
adds a lot more drag and really increases the adverse drag. The
upward moving aileron function reduces the drag a little, but doesn't
remove much lift, again resulting an adverse yaw but no real rolling
effect. In the models you can change the "rate" of the controls
(increase or decrease the deflection relative to the control stick
input) and overcome some of the rolling problems but not very much.
We don't have any mechanism in our "big" sailplanes (that I know
about) that can increase the deflection of a surface at different
airspeeds or by selecting a mechanical detent on a control.

Having tried full-span flaperons in the model form, several times, I
can say I'd rather not try them on a full size, where my life is on
the line.

Mike