Fly-by-wire and gliders

[krasw]

We have not seen much performance increase with new gliders for couple of decades, other than increased wingloading. I wonder if anyone has run the numbers for glider with FBW steering. I'm thinking of flapped glider with multiple moving segments of flaps (independent servos) and very small rear fuselage/tail, possibly with only minimal elevator (like Genesis2). Designed stability would not be issues as FBW brain would keep nose pointed to where you want all the time, glider could be aerodynamically unstable like modern fighter. Rudder authority would not be issue as yaw could be partly controlled with outboard flaps acting as spoilers, possibly airbrakes could be done with flaps only, FBW would adjust for configuration changes. Probably rudder pedals could be "optional" as FBW could keep "yaw string" centered. No need for control lines or flap mixers. Power for FBW and servos would need few bigger lithium batteries.

I'm visioning glider flying into thermal, where you just press "auto-thermal" and enjoy scenery.

[JS]

Auto-Thermal scenery would have been enjoyable yesterday, where the strongest lift was frequently towards the wall of granite.
Jim

[Steve Leonard[_2_]]

On Thursday, October 30, 2014 12:20:10 PM UTC-5, krasw wrote:
> We have not seen much performance increase with new gliders for couple of decades, other than increased wingloading. I wonder if anyone has run the numbers for glider with FBW steering. I'm thinking of flapped glider with multiple moving segments of flaps (independent servos) and very small rear fuselage/tail, possibly with only minimal elevator (like Genesis2). Designed stability would not be issues as FBW brain would keep nose pointed to where you want all the time, glider could be aerodynamically unstable like modern fighter. Rudder authority would not be issue as yaw could be partly controlled with outboard flaps acting as spoilers, possibly airbrakes could be done with flaps only, FBW would adjust for configuration changes. Probably rudder pedals could be "optional" as FBW could keep "yaw string" centered. No need for control lines or flap mixers. Power for FBW and servos would need few bigger lithium batteries.
>
> I'm visioning glider flying into thermal, where you just press "auto-thermal" and enjoy scenery.

I would hazard a guess that you haven't flown an older ship against a newer ship if you believe that the only difference is wing loading. The older airfoils "went to worms" with rain or bugs, or if you pulled a wee bit too hard in the thermal.

FBW is not going to boost glider performance. Glider performance comes from laminar flow and lack of separated flow much more than from reduced stability and a computer working to keep you pointed where you think you want to go.

And, there are certain sailplanes that already let you sit back and enjoy the scenery while thermalling. And they don't require FBW. Unless you consider the 7 x 19 cables that are hooked from the control surfaces to the pilot input devices. :-)

Just my two cents worth.

Steve

[Luke Szczepaniak]

On 10/30/2014 1:20 PM, krasw wrote:
>
> I'm visioning glider flying into thermal, where you just press "auto-thermal" and enjoy scenery.
>

Is that what you really want? Whats the point? Why not just pop in a
National Geographic blu-ray on your 80" plasma and enjoy the scenery on
the couch?

Luke

[Tony[_5_]]

On Thursday, October 30, 2014 12:20:10 PM UTC-5, krasw wrote:
> We have not seen much performance increase with new gliders for couple of decades, other than increased wingloading. I wonder if anyone has run the numbers for glider with FBW steering. I'm thinking of flapped glider with multiple moving segments of flaps (independent servos) and very small rear fuselage/tail, possibly with only minimal elevator (like Genesis2). Designed stability would not be issues as FBW brain would keep nose pointed to where you want all the time, glider could be aerodynamically unstable like modern fighter. Rudder authority would not be issue as yaw could be partly controlled with outboard flaps acting as spoilers, possibly airbrakes could be done with flaps only, FBW would adjust for configuration changes. Probably rudder pedals could be "optional" as FBW could keep "yaw string" centered. No need for control lines or flap mixers. Power for FBW and servos would need few bigger lithium batteries.
>
> I'm visioning glider flying into thermal, where you just press "auto-thermal" and enjoy scenery.

Windward has at least one Duckhawk flying with auto-flaps...

[Ernst]

Condor?

Ernst

[Cookie]

I have worked with "Freedom's Wings International" for a few years now...(Flying for Pilots with Disabilities.)

Our gliders are fitted with "hand control" for rudder. The problem arises that the pilot must let go of the rudder control, to deploy the spoilers.....the spoilers are "notched" so they stay put, and the pilot goes back to rudder quickly....but a change in spoiler setting repeats the process...

After seeing a Duckhawk with electric flaps, and electric landing gear...I figured it would be nice to configure a glider with electric spoilers....Then there would be no need to take the hand off the rudder control....just push a button, or slide switch or whatever!

Of course radio controlled model gliders have everything fly by wire!


Cookie

[Bob Kuykendall]

One of the main issues with FBW is that there is relatively little in the way of off-the-shelf components of the right size and power to build the control systems out of. What OTS components are available from the world of sailplane-sized UAVs tend to be priced commensurately the low volume and specialized applications for which they were designed--which is to say, really freakin' expensive.

If somebody wants to jump into the market and make a line of high-reliability, low-power, servos and sensors and such, along with a networked FMS to run it all, I'm sure they could build it into quite a business in ten or twenty years or so.

[Ramy[_2_]]

While I am not looking forward for any automatic controls, I agree with the OP that FBW will significant improve performance. I believe the lost of performance due to inaccurate pilot input, un centered yaw string (heavy foot), non optimal flap position (I estimate I am flying in non optimal flap position maybe 30% of the time especially when doing a lot of transitions), flying too slow/too fast etc hurts performance more than the difference in glide performance between modern gliders.

Ramy

[Dan Marotta]

so... You want to eliminate all the things that make soaring challenging?

Dan Marotta

On 10/30/2014 6:04 PM, Ramy wrote:
> While I am not looking forward for any automatic controls, I agree with the OP that FBW will significant improve performance. I believe the lost of performance due to inaccurate pilot input, un centered yaw string (heavy foot), non optimal flap position (I estimate I am flying in non optimal flap position maybe 30% of the time especially when doing a lot of transitions), flying too slow/too fast etc hurts performance more than the difference in glide performance between modern gliders.
>
> Ramy

[Ramy[_2_]]

On Thursday, October 30, 2014 6:13:41 PM UTC-7, Dan Marotta wrote:
> so...* You want to eliminate all the
> things that make soaring challenging?
>
> Dan Marotta
> On 10/30/2014 6:04 PM, Ramy wrote:
>
>
>
> While I am not looking forward for any automatic controls, I agree with the OP that FBW will significant improve performance. I believe the lost of performance due to inaccurate pilot input, un centered yaw string (heavy foot), non optimal flap position (I estimate I am flying in non optimal flap position maybe 30% of the time especially when doing a lot of transitions), flying too slow/too fast etc hurts performance more than the difference in glide performance between modern gliders.
>
> Ramy

No no, I don't want this, just agreeing with the OP that this will indeed improve performance, but in the account of fun and challenge.

Ramy

[krasw]

On Friday, 31 October 2014 02:04:10 UTC+2, Ramy wrote:
> While I am not looking forward for any automatic controls, I agree with the OP that FBW will significant improve performance. I believe the lost of performance due to inaccurate pilot input, un centered yaw string (heavy foot), non optimal flap position (I estimate I am flying in non optimal flap position maybe 30% of the time especially when doing a lot of transitions), flying too slow/too fast etc hurts performance more than the difference in glide performance between modern gliders.
>
> Ramy

Yes and we have to remember that whole concept of conventional glider with tail has built-in-drag as elevator pushes the tail down all the time instead of giving only occasional control inputs. I bet there is several extra % of drag right there, as is in the large wetted area of long rear fuselage and rudder, which is only needed to counteract the yaw created by aileron drag. Flight controls have to be designed to have nice feel and harmony. Would there be more aerodynamically optimal geometries if this would be a non-issue? You could program any control feel you wish to joystick.

New wingprofiles (current are from nineties BTW, Ventus 2 & ASW 27 etc.) could be used with more narrow area of optimum angle-of-attack as FBW could nail it indefinetly while thermalling.

One could speculate with safety aspects as well. FBW would be easily programmed with unability to stall. Think about it, only coordinated turns, if you pull the stick while thermalling low, nose would go up until close to stalling angle of attack but not an inch more.

I believe hardware is coming cheaper and easily available as this is all stuff that UAVs use right now. You probably got most of the required sensors in your pocket right now. And I bet that at least some Akaflieg have studied this concept already.

Would we want FBW controlled glider? Did we want glider made from glassfibre instead of wood during 60s? Electrical varios during 70s? Or GPS in 90s? PW5? (No wait, no-one wanted that.)

THEY ALL RUINED THE SPORT when introduced, remember? :)

[Ramy[_2_]]

One thing to consider is what will happen when the FBW will fail from some reason and you end up with pilots who don't know how to fly manually as happened to AF447.

Ramy

[Vaughn]

On 10/31/2014 3:22 PM, Ramy wrote:
> One thing to consider is what will happen when the FBW will fail from
>some reason and you end up with pilots who don't know how to fly
manually as happened to AF447.
>
> Ramy
>
Are you saying that simply pushing the "Return to Gliderport" button
might not always be an option?

Vaughn

[J. Nieuwenhuize]

FBW is the only reasonable way to get rid of the tail surfaces. That's easily 20% of the total drag and an easy 10% of the weight. All in all, I would think a 35-50% increase in performance is possible, once one can deal with the huge issues of implementing a FBW.

[Francois VG]

20+ years ago, I flew this Speed Canard ( http://en.wikipedia.org/wiki/Gyroflug_Speed_Canard ) . No tail stabilizer, no FBW, and flying it didn't require any special skill (I've never had any ;-) ). Nice to fly. It actually even wouldn't stall.
I guess this proves that instability is actually not a problem. Indeed, if the speeds unwillingly increases, we don't wait for stability to correct, we pitch up ourself well before !
Or do I get it wrong ?

[Martin Gregorie[_5_]]

On Tue, 04 Nov 2014 01:53:34 -0800, Francois VG wrote:

> 20+ years ago, I flew this Speed Canard (
> http://en.wikipedia.org/wiki/Gyroflug_Speed_Canard ) . No tail
> stabilizer, no FBW, and flying it didn't require any special skill (I've
> never had any ;-) ). Nice to fly. It actually even wouldn't stall.
> I guess this proves that instability is actually not a problem. Indeed,
> if the speeds unwillingly increases, we don't wait for stability to
> correct, we pitch up ourself well before !
> Or do I get it wrong ?

As I understand it, the main problem with flying wings is that, contrary
to popular superstition, they are not particularly efficient due to the
reflexed wing sections that are often used on flying plank designs, i.e.
no or minimal sweepback, and the often extreme amounts of wash-out that
many swept wing designs need to be stable.

In the competition free flight model world, which requires models to be
auto-stable since they are not remotely controlled, you never see flying
wings in competition with conventional layouts and the designs flown in
specialist tailless competition classes have clearly inferior performance.

Its also noticeable that contemporary 'tailless' high performance gliders
and light aircraft such as the Genesis II, Gyroflug Speed Canard and
VariEZE are *not* tailless designs.

If anybody on the list has flown a true tailless glider, such as the
Hortens or the French Fauvel designs, it would be interesting to hear how
they rate their performance against similar conventional designs.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Dan Marotta]

"...no tail stabilizer..."

What do you call that canard? ...And those vertical thingies on the
wing tips...

Dan Marotta

On 11/4/2014 2:53 AM, Francois VG wrote:
> 20+ years ago, I flew this Speed Canard ( http://en.wikipedia.org/wiki/Gyroflug_Speed_Canard ) . No tail stabilizer, no FBW, and flying it didn't require any special skill (I've never had any ;-) ). Nice to fly. It actually even wouldn't stall.
> I guess this proves that instability is actually not a problem. Indeed, if the speeds unwillingly increases, we don't wait for stability to correct, we pitch up ourself well before !
> Or do I get it wrong ?

[Andrew[_14_]]

I've been intrigued by the no horizontal stab idea for that reason. A clever fellow implemented a simple control system on a model sailplane and was able to achieve this. He explains the design problem really well too. Here's the page for those interested.
http://www.charlesriverrc.org/articles/asfwpp/helmutlelke_asfwpp.htm

I wonder what performance hits there may be while thermalling? This is a problem that the Genesis I/II faces.

I'd love to try it on a model glider, but not on full-scale. Too easy to imagine what happens if the angle of attack sensor vane fails... aka the X-31 crash and so on...

On Saturday, November 1, 2014 7:17:12 AM UTC-4, J. Nieuwenhuize wrote:
> FBW is the only reasonable way to get rid of the tail surfaces. That's easily 20% of the total drag and an easy 10% of the weight. All in all, I would think a 35-50% increase in performance is possible, once one can deal with the huge issues of implementing a FBW.

[Mike the Strike]

Show me a soaring bird without movable tail surfaces, then I might consider it!

Mike

[Vaughn]

On 11/4/2014 1:48 PM, Mike the Strike wrote:
> Show me a soaring bird without movable tail surfaces, then I might consider it!
>
> Mike
>
Well yes, but by that logic all gliders should be self-launchers
propelled by wing flapping.

Vaughn

[krasw]

On Tuesday, 4 November 2014 21:38:14 UTC+2, Vaughn wrote:
> On 11/4/2014 1:48 PM, Mike the Strike wrote:
> > Show me a soaring bird without movable tail surfaces, then I might consider it!
> >
> > Mike
> >
> Well yes, but by that logic all gliders should be self-launchers
> propelled by wing flapping.
>
> Vaughn

Touché!