I have a new GJC F4D Skyray that will debut in the spring. Reading reports from other owners, it appears that the plane tends to dutch roll at certain speeds. Increased wing loading increases the dutch roll tendancy. Installation of a gyro on the roll axis is recommended. Being an elevon style delta wing the servo will handle both aileron and elevator functions. I am looking for a gyro that will work with this system. Most gyros I have seen are single input, single output meaning I would have to 'Y' connect the ailerons and I don't believe that will work because of the elevator requirements. I could put the gyro on only one aileron but I'm not sure that that will be effective. Futaba offers a dual in - out gyro that I've heard is intended for elevon designs. Other than the need to modify the connectors to fit my JR system, will the Futaba Gyro work with a JR radio?

Dutch roll as I understand and have had it on BVM Bobcats and KingKats in crosswinds are effectively dealt with a gyro on the YAW axis or rudder channel. Full 3 channel axis gyros as you beilieve you need are available now in quad copters and flybarless helis. Then their are two types of gyro correction, heading hold or yaw dampening.

Do we need to go further, just ask. I am a heli pilot well versed in gyros for 26 years, as well as jet jock for 12.

AMA26390

C/F, if I can handle the dutch roll with rudder, then I don't have any questions. I'm just trying to understand how I would hook up a gyro to an elevon system to control only roll with the ailerons and not interfere with the elevator.

Thanks for your input. I may be back to you.

This is a topic that has been covered many times before. If you use the well known ACT gyro (2 versions) you connect the elevon servos to the Gyro and plug the output cables into the receiver. The unit is oriented to give the correct corrections for the axis you want, in this case ailerons. The ony changes made to the flying will be corrections to uncommanded inputs making the flying smoother. The elevon elevator commands are not affected.

Have a look at the manual. The first half is in German the second in English with some diagrams.

http://www.acteurope.com/intanlfuzzypro3.pdf

John

I think you could also use two standard gyros, one on each servo. Orient the gyros so they respond to the roll axis and make sure they are correcting in the proper direction. Pitch/elevator control would be unaffected.

Make sure gyros are not set to "heading hold" mode.

KennyMac

That may cover the question of a single yaw dampening gyro action of elevon flight controls. But I'm curious if the "DUTCH ROLL" which acts as a yaw wiggle is more effectivley handled with an axis or yaw correcting inputs?

Or a elevon mixer and two gyros one for roll, one for pitch.


http://www.electrodynam.com/rc/EDR-116/index.shtml

Dutch roll is initiated by oscillation in yaw. The yaw roll coupling of a swept wing (acts like dihedral) then causes an oscillation in roll. So putting a gyro on ailerons stops the roll but still leaves the fishtailing. Putting a gyro on rudder stops the fishtailing which stops the rolling too. That's why full size primarily use yaw dampers when no roll dampers are fitted. However some models with highly swept wing can have a very high gain of yaw to roll, meaning the very slight yaw that a gyro must allow may translate to a tiny and just noticeable wing rock. (A rate mode gyro can not prevent rotation, for some rotation must exist in order for the gyro to sense it, what the gyro does is stop the rotation after a much smaller angle than a human reactions can) Therefore sometimes for the sake of aesthetics it is better to have the gyro on ailerons to stop the wing rock and just accept the very little, barely noticeable fishtailing. The fishtailing will actually be reduced by the aileron gyro because in Dutch roll there is feedback from the roll angle causing sideslip which causes a yawing. Ideally you would have both yaw and roll gyros, setting the yaw gyro first and then the aileron gyro to remove any last bit of wing rock that is left.

As mentioned by John Wright, there are gyros such as the ACT Fuzzy Pro that have 2 channels in and 2 out to cope with ailerons and elevons. I use the ACT Fuzzy Pro for the elevons of my Eurofighter Typhoon. I think Futaba and JR also have dual channel gyros. One thing to beware of is that elevons often have much smaller aileron travel than elevator travel, so the aileron gyro will typically only need the lowest of gains. If you set up your Tx gyro gain travels to the normal defaults so that you can set up the gyro in flight, it will be very coarse and may go into over-gain too easily, so if the ail travel of your elevons is much less than the ele travel, turn down the gyro max gain travel in the tx to get a finer control. Another snag with elevons is the gyro's fade out is based on full elevon travel. So if the ele travel is greater than the ail travel, instead of fading out to 0% gyro at full aileron, it will only be down to say 50% fade out and you get a very reduced roll rate. Therefore after flight testing to establish the correct gain, I mix the aileron stick to the gyro gain channel and program a multi-point curve so that the aileron stick controls the gain and makes the gyro fade out properly. The gyro's action has an exponential effect so you can expect to reduce or even cancel Tx expo.

H

+1

That is true and correct....

We have the ACT Fuzzy Pro SMM Jet gyros in stock, ready to ship.

Chad

There is a flaw in the software of the ACT gyro that I have but it is a few years old now and perhaps it was corrected in the later revised versions such as the Fuzzy Pro Jet gyro. The flaw only applies when it is used with elevons and is only apparent when the aileron travel is less than the elevator travel.

I alluded to the problem in my earlier post. Let’s assume that if the gyro gain is 100%, it is able to make the servo rotate 100% of its normal travel, 50% gain lets the gyro rotate the servo 50% of its normal travel and so on. So you need to define to the gyro what a normal travel is, because you may have a different travel value to 100% in your tx settings, and anyway different brands of tx send different travel values at the default 100%. The ACT gyro allows you to tell it the normal travel by putting it into a learning mode and moving the aileron stick. Thus the gyro learns what the max travel of the aileron is and can calibrate its 100% level to that travel.

That sounds fine, but hopefully you are watching the model very carefully during set-up in the workshop and just happen to notice that the elevator travel is much reduced. What has happened is that the ACT gyro software has not just calibrated its response to the aileron travel, but is using that as a max travel that it allows to pass through it, so it is limiting the elevator travel to be the same as the aileron.

What you then have to do is re-teach it the travel but using the elevator. The result is that the gyro now calibrates its 100% effect to be the same as the elevator travel which may be 2 or 3 times the aileron travel! And that has 2 major implications –

1. You may find that the correct gyro setting would have been 10%, that is it is allowed to deflect the ailerons 10% of their travel. But because it has calibrated to the elevator travel and lets say that is 3 times the aileron travel, 10% gyro gain comes to 30% deflection of the ailerons. To get the aileron to deflect 10% by gyro means a gain of just 3%. If your tx gain channel is left at the normal 0 to 100% travel, every step of travel of the rotary knob or slider will give, in effect, 3 times the gain so it becomes a very coarse control, and capable of easily putting the gyro into much too high a gain so that it starts oscillating wildly. Changing down the Tx travel to the fraction of ail/ele travel will correct that and allow better adjustment.

2. The ACT fade-out will not work properly. It is based on reducing the gyro gain until at full stick the gain is reduced to zero. But it has been calibrated to elevator travel value, not aileron travel value, so it only reduces the gain by the fraction of ail/ele travel, thus at full aileron stick you still have a lot, perhaps most of the gain and the roll rate is massively reduced. My way around it is to turn off the gyro fade-out option, and having found out the travel value for the gain from the dedicated slider/rotary knob on the Tx during flight testing, re-assign the gain to the aileron stick with a V shaped curve where the apex of the V is the travel value established in testing and the ends of the V are 0 %. That way the gyro gets a gain signal that varies as you move the aileron stick so at full aileron stick the gyro gain channel is getting the 0% centre travel signal and its gain reaches zero. (centre signal is no gain, travel in one direction increases rate mode gain, travel in the other direction puts it into HH mode and gain). I actually use multi point curves and move the gain to zero well before full stick travel but that is just my preference.

Phew, who would have thought that adding a “simple” gyro to elevons could be so complicated!

H.

Hi guys! I am on the way to buy an Eurosport 3d universe. I want to use an iGyro to control ail, ele VT and rudder VT and a separate gyro for canards (if needed)

There are 2 different opinions:

1. Some guys recommend to use 2 gyros, one for elevator/pitch and one for yaw/rudder vectors. Ok. I agree but I cannot unerstand what really these gyros do for me! I understand the yaw gyro will correct me the plane during a roll (we know that a plane intend to yaw to right if the plane roll to left). In this situation the gyro will do the correction for me. Am I correct? But I cannot understand what the elevator (elevon) gyro do for me insteed of the fact that helps me when an external force comes on the plane (wind)?

2. the 2 Germans flying the J-10's have totally 4 gyros: 2 gyros on VT, one on roll (elevons) and one on canards. Oh my god!
What am I thinking is as follows (but not sure): Please correct me if I am wrong! I am thinking at the following setups: Which setups you consider the best (or other modes are welcomed)

MODE1 I assume the plane is tail havy
Canards connected independently on a gyro1 to correct the pitch movement (plane tend to pitch up because tail havy), elevator mixed with TV, gyro2 on aileron, gyro 3 on rudder
So, in this case the plane will take-off short thanks to the VT and the unwanted pitch movement is corrected by the canard gyro 1 because there are enough airflow on the plane. Is it correct?
This setup will help me also in level flight because the canard will make me all the pitch corrections.
Do you think that the purpose of using the gyro on canards is to make the plane more stable in flight? I cannot see other explanation because in high alfa or hovering the gyro1 has NO effect only during flight! The job in slow flight could be made only by VT pitch gyro. ! What do you think?

Mode 2: I assume the plane is balanced properly
canard mixed with elevator, elevator mixed with VT and VT gyro 4, ailerons connected to gyro2, rudder on gyro3, no gyro on canard (or?)

What happen in this mode in slow flight? The pitch VT gyro 4 is ON but it is really active only when the elevator stick is in the neutral position or an external force appear!!Same for gyro2 on ailerons! if i pull or push the elevator stick the gyro doesn't work! Could somebody explain me what really such gyro4 on elevator VT can do for me and when?


These are my oppinions theoretically!! Could somebody explain me other setup opinions for an eurosport or other canard plane?
To use 2 gyros or 4? Why 2 and why 4? what are my benefits?

i would very much appreciate your help

thanks

Zoli