Reversal of bank with no roll input

aeronaut999 · Nov 19, 2012, 01:08 PM

I want to configure one of my RC gliders to replicate something I've observed in my hang gliders. When I have the glider in a banked attitude and give a nose-down pitch up with no roll input, I want to the glider roll through wings-level and on into a bank in the opposite direction. A roll reversal accomplished with no roll input.

Starting with a 4-servo-wing glider (flaps and ailerons can all be positioned independently), how would you configure the glider to respond in this manner to a pitch-only control input? Any ideas?

Steve

ShoeDLG · Nov 19, 2012, 04:00 PM

So you want the glider to roll in response to pitch inputs. You mentioned that you have flaps and ailerons. If you want this to work in both directions, then you would have to deflect the ailerons and flaps symmetrically (if at all) in response to a pitch input. This would also rule out rudder deflection in response to a pitch input. This sounds like an objectionable flying quality, not sure why you'd want to reproduce it.

vespa · Nov 19, 2012, 06:03 PM

I don't know what a "nose down pitch up" is nor can I imagine the purpose of your goal but it sounds like you are seeking severe Dutch roll. This is pretty easy to design in, simply reduce yaw stability as much as possible while greatly increasing roll stability. Where most aircraft use dihedral for roll stability, hang gliders use sweep and pendulum effects to provide a roll stability that varies widely with AoA and dynamics. With no vertical fin and enormous roll stability the Dutch roll is extremely severe but can be varied in magnitude or even reversed with perfectly timed pitch input.

BMatthews · Nov 19, 2012, 06:56 PM

I would say that this is one place where the charactaristics of a wing only hang glider that is controlled by weight shifting is simply not going to be in any way transferrable to a conventional model.

You can't even mix this in, not that it would be a good idea anyway, since the mix has no way of knowing which way the model is banked and therefore which way to roll it.

The only way you'll get a design to do what you want is to make a weight shift controlled hang glider model that faithfully models the one you're used to flying. What you're describing just doesn't happen in any way or form for "normal" tailed designs.

Nov 19, 2012, 01:08 PM	#1
aeronaut999 Registered User The Willamette Valley, Oregon Joined Dec 2008 712 Posts	Reversal of bank with no roll input I want to configure one of my RC gliders to replicate something I've observed in my hang gliders. When I have the glider in a banked attitude and give a nose-down pitch up with no roll input, I want to the glider roll through wings-level and on into a bank in the opposite direction. A roll reversal accomplished with no roll input. Starting with a 4-servo-wing glider (flaps and ailerons can all be positioned independently), how would you configure the glider to respond in this manner to a pitch-only control input? Any ideas? Steve

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Nov 19, 2012, 04:00 PM	#2
ShoeDLG Registered User Germany, BW, Stuttgart Joined Mar 2012 488 Posts	So you want the glider to roll in response to pitch inputs. You mentioned that you have flaps and ailerons. If you want this to work in both directions, then you would have to deflect the ailerons and flaps symmetrically (if at all) in response to a pitch input. This would also rule out rudder deflection in response to a pitch input. This sounds like an objectionable flying quality, not sure why you'd want to reproduce it.

Nov 19, 2012, 06:03 PM	#3
vespa Hardware in the loop Thousand Oaks, CA Joined Mar 2004 1,888 Posts	I don't know what a "nose down pitch up" is nor can I imagine the purpose of your goal but it sounds like you are seeking severe Dutch roll. This is pretty easy to design in, simply reduce yaw stability as much as possible while greatly increasing roll stability. Where most aircraft use dihedral for roll stability, hang gliders use sweep and pendulum effects to provide a roll stability that varies widely with AoA and dynamics. With no vertical fin and enormous roll stability the Dutch roll is extremely severe but can be varied in magnitude or even reversed with perfectly timed pitch input.

Nov 19, 2012, 06:56 PM	#4
BMatthews B for Bruce The 'Wack, BC, Canada Joined Oct 2002 9,447 Posts	I would say that this is one place where the charactaristics of a wing only hang glider that is controlled by weight shifting is simply not going to be in any way transferrable to a conventional model. You can't even mix this in, not that it would be a good idea anyway, since the mix has no way of knowing which way the model is banked and therefore which way to roll it. The only way you'll get a design to do what you want is to make a weight shift controlled hang glider model that faithfully models the one you're used to flying. What you're describing just doesn't happen in any way or form for "normal" tailed designs.