Full-span flaperons as airbrakes?

On Mar 7, 11:40*am, Bruce wrote:
Frank Whiteley wrote:
On Mar 6, 8:12 pm, Bret wrote:
Hi, do any gliders have full-span flaperons that also act as airbrakes
(say at 70-90 degree), or do you lose all aileron authority when the
flaperons are that deflected?

Kestrel 19 has full span flaperons. *The inboard section, in climb and
cruise settings, deflects half the range of the outboard sections. *A
second, panel mounted, landing flap handle, allows half or full
landing flap deflections of the inboard sections, to a maximum of 35
degrees. *This generates high drag and lift for glide path control
when landing. *Half landing flap may be used when ground launching and
will add 200ft or more to the launch height. *Derek Piggott has
described it as a rather complex cockpit as gliders go, as there are
also air brakes and a tail chute.

Frank Whiteley

Rather complex? Surely not.

You establish a nice steady final approach using thermal flap so you can
see the runway over the very high instrument panel.
Then you use your left hand to select 55-70kt flap (-2) - flaps forward
Then you reverse direction with the same hand and pull the separate
landing flap lever backwards to half or full flap. Best be sure you can
make the field before you do this as dumping the landing flap will
result in a lot of lost height and full landing flap steepens the
approach appreciably.
Simultaneously you use your other left hand to control the finer
approach sink rate with the modest airbrakes.
Maybe there is reason in this - you effectively have to allow the
airbrakes to retract as you apply landing flap.

While doing this you maintain roll and pitch control with your right and
on the stick, and adjust the trim using the trigger on the base of the
stick with your little finger.
Did I mention that you had best have not neglected to lock the
undercarriage down with your right hand on downwind. If not you use your
other right hand to do it now.
In the event that you are too high - or approaching a very short field
over obstacles you may want to deploy the parachute.
Now there are three identical feeling little handles down there between
the stick and the panel. Remember the left most will operate the cable
release, no use to you here. The left of centre one will release the
parachute in case you no longer want it and the little fairing for the
rudder... And the one you want is on the right hand side under your
thigh (inevitably) So you can use your other right hand to dig it out
and yank HARD. Then nothing happens till you wiggle the rudder, at which
point it is best to have already lowered the nose to counter the
surreptitious slow down. At this point - if you can see it over your
toes it is out of glide range.

Then you might want to pull the left hand (but not cable release) handle
to jettison the parachute as you cross the fence - in case the parachute
hooks on something well anchored (like a fence). In his instance it is
useful to have another left hand available as the airbrakes will tend to
close without something to hold them open, and the fence at the other
end of the field may be looming.

In practice it all works quite well, the Kestrel is very stable and
tolerates the hand swapping and general fidgeting - but it is a cockpit
you need to know before you try to fly it. There are lots of separate
controls in close proximity - and the correct combinations are important
lest the beastie rise up and bite you.

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

Okay, Derek didn't say complex, he said complicated
http://www.glidingmagazine.com/Featu...cle.asp?id=111

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

I don't know of any sailplane design that uses full span single surface
flaperons.


I know I'm getting in late on this but the original LS-3 had one full-
span control surface per wing panel. It was fairly flexible (said
anyone who ever removed one from the wing for maintenance) and
apparently required a fair amount of lead to mass balance (IIRC, 40
lbs. was mentioned, probably split between left and right). The result
was that the wings were not only quite heavy (175 lbs.each) but the
balance was biased towards the trailing edge, making it more awkward
to handle during rigging. Maximum flap settings were -7 to +10
degrees, probably to prevent the one-piece surface from distorting or
even splitting/buckling at the trailing edge at higher wing
deflections. The wing itself was very stiff (probably another reason
for its weight since this was pre-carbon fibre) so the deflection in
turbulence was low (read: it was a rough ride on the ridge). It sounds
a little odd but the glider was a joy to fly and both climbed and ran
very well when new. Alas, LS-3s experienced shrinkage over the spar
caps over time, which hurt the cruise performance though they still
climbed well. Some owners (including me) sanded and/or added gel coat/
filler to restore the original profile and the glider was transformed,
making it equal to the ASW 20, Ventus, and LS-6 of its day. It's still
a great, wonderfully strong airplane with a lot of performance that
gives its owners a great deal (for one with a good finish).

Not to be confused with the LS-3a or LS-3 17, both of which had more
conventional flap/aileron control surfaces and lighter wing panels.

Chip Bearden
ASW 24 "JB"
USA

On Mar 19, 2:58*pm, Chip Bearden wrote:
I don't know of any sailplane design that uses full span single surface
flaperons.

I know I'm getting in late on this but the original LS-3 had one full-
span control surface per wing panel. It was fairly flexible (said
anyone who ever removed one from the wing for maintenance) and
apparently required a fair amount of lead to mass balance (IIRC, 40
lbs. was mentioned, probably split between left and right). The result
was that the wings were not only quite heavy (175 lbs.each) but the
balance was biased towards the trailing edge, making it more awkward
to handle during rigging. Maximum flap settings were -7 to +10
degrees, probably to prevent the one-piece surface from distorting or
even splitting/buckling at the trailing edge at higher wing
deflections. The wing itself was very stiff (probably another reason
for its weight since this was pre-carbon fibre) so the deflection in
turbulence was low (read: it was a rough ride on the ridge). It sounds
a little odd but the glider was a joy to fly and both climbed and ran
very well when new. Alas, LS-3s experienced shrinkage over the spar
caps over time, which hurt the cruise performance though they still
climbed well. Some owners (including me) sanded and/or added gel coat/
filler to restore the original profile and the glider was transformed,
making it equal to the ASW 20, Ventus, and LS-6 of its day. It's still
a great, wonderfully strong airplane with a lot of performance that
gives its owners a great deal (for one with a good finish).

Not to be confused with the LS-3a or LS-3 17, both of which had more
conventional flap/aileron control surfaces and lighter wing panels.

Chip Bearden
ASW 24 "JB"
USA

And due to the lead in the wings, the German speakers in this group
will understand why the "LS-Drei" was referred to as the LS-Blei"...


Ray Lovinggood
Carrboro, North Carolina, USA