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#11
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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 |
#12
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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. |
#13
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Full-span flaperons as airbrakes?
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 |
#14
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Full-span flaperons as airbrakes?
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: --- |
#15
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Full-span flaperons as airbrakes?
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) |
#16
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Full-span flaperons as airbrakes?
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 |
#17
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Full-span flaperons as airbrakes?
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? |
#18
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Full-span flaperons as airbrakes?
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 |
#19
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Full-span flaperons as airbrakes?
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 |
#20
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Full-span flaperons as airbrakes?
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 |
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