Low vs. High Gyro Gains
11-30-2020, 07:55 AM
#1
Low vs. High Gyro Gains
Just wondering what's the typical difference in gain values. I realize that every application is different, so I'm just looking for a ball park number.
I've dialed in my gain for normal flying and am looking for a plug number to increase it when my retracts are down. This is just a starting point and I'll fine tune it from there. I was thinking that about +10 would be a good starting point, however in speaking to a friend at the field he's adding about 40, which seems excessive.
Yes, I know I could put it on a dial but I prefer to start with a best guess number and fine tune it using a trim tab.
I've dialed in my gain for normal flying and am looking for a plug number to increase it when my retracts are down. This is just a starting point and I'll fine tune it from there. I was thinking that about +10 would be a good starting point, however in speaking to a friend at the field he's adding about 40, which seems excessive.
Yes, I know I could put it on a dial but I prefer to start with a best guess number and fine tune it using a trim tab.
11-30-2020, 08:10 AM
#3
I personally start at 22% and gradually increase. I am also flying PB Mercury with GPS speed gain adjustment in 3 of my jets. When I set up a new student, I start at 22%. On Low rates, I'm only flying 10-15% expo in the transmitter. I've also used 22% on a Cortex too. You need to understand the difference between adding gain on the gyro, verses expo on the controls.
11-30-2020, 08:32 AM
#4
My Feedback: (3)
Which gyro are you using? Using a Cortex Pro, I’m typically in the 30-40% range for flaps up and 50-60% for full flaps landing config. You may be able to go a little higher but this works for me.
I have my flaps on flight modes and as I select each flap position the gyro gain changes automatically ... that way I don’t have to remember to change gyro gain when setting up to land. I have a separate master on/off for the gyro for emergency use.
I have my flaps on flight modes and as I select each flap position the gyro gain changes automatically ... that way I don’t have to remember to change gyro gain when setting up to land. I have a separate master on/off for the gyro for emergency use.
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JackD (11-30-2020)
11-30-2020, 08:39 AM
#5
I personally start at 22% and gradually increase. I am also flying PB Mercury with GPS speed gain adjustment in 3 of my jets. When I set up a new student, I start at 22%. On Low rates, I'm only flying 10-15% expo in the transmitter. I've also used 22% on a Cortex too. You need to understand the difference between adding gain on the gyro, verses expo on the controls.
This is the poor mans way, bump the gain with the gear switch so you get more gain when you slow down to land.
11-30-2020, 08:46 AM
#6
I was told by several folks and read it someplace that Expo on the transmitter should be minimized when using a gyro because Expo tends to negatively affect the Gyro's end result. Not that you have to totally eliminate Expo. You just cut it back significantly. I cut mine back arbitrarily 50% when I install gyros.
Also, I have found that different brand's gyros react differently to their gain settings. Different brand gyros end up with different range settings. For example: The AS 3000 (AS3X) starts out with 40/50/60 on the Aile/Elev/Rudd respectively. Where as my Mercury's Igyros are good at 25% (low) and 35% (High). On the Igyro, if I increase the gain over the low speed setting by > 10% for High Rates, my planes tend to get a bit erratic when at mid-speeds. The Igyro's GPS module appears to help at higher speeds, but does not cure this. Put the Gyro's rate on the Flap switch at full flap and most of this is solved by the speed you fully engage the flaps, etc..
A +40% jump for High Rates seems like a lot to me too. But, I have seen, when helping folks with their setups, that some folks seem to set their gyros at minimal gain and other folks set the gain just under the max. What ever works well, has got to be good. Right?
Also, I have found that different brand's gyros react differently to their gain settings. Different brand gyros end up with different range settings. For example: The AS 3000 (AS3X) starts out with 40/50/60 on the Aile/Elev/Rudd respectively. Where as my Mercury's Igyros are good at 25% (low) and 35% (High). On the Igyro, if I increase the gain over the low speed setting by > 10% for High Rates, my planes tend to get a bit erratic when at mid-speeds. The Igyro's GPS module appears to help at higher speeds, but does not cure this. Put the Gyro's rate on the Flap switch at full flap and most of this is solved by the speed you fully engage the flaps, etc..
A +40% jump for High Rates seems like a lot to me too. But, I have seen, when helping folks with their setups, that some folks seem to set their gyros at minimal gain and other folks set the gain just under the max. What ever works well, has got to be good. Right?
11-30-2020, 08:48 AM
#7
On both my Cortex (Savex L-39 and DerJet Hunter) and Cortex Pro (Ultra Flash) equipped models, I am around 30% Tx gain flaps up, 60% flaps mid (take off) and 100% full flaps.
I do not select gyro gain on gear position, but rather use flap setting (Flight Mode) as the flap position determines the speed range to fly, not the gear position.
The other week I took my laptop with me and fine tuned the Cortex in the little Savex L-39. Roll would be the first axis to enter an oscillation, and over the course of 3 flights I managed to dial down the roll axis internal gain and turn up the gain on the pitch and yaw axes. I reached the stage that I have the pitch and yaw axes turned up the maximum allowed internal gain. With full flap and the Tx gain set to 100% I still can't get it to oscillate in either pitch or yaw axis. The roll axis is turned down so that at 100% Tx gain it won't oscillate either. I reached these settings with full flap selected, and then just dialed back the overall Tx gain for mid flap and flaps up to be oscillation free at the highest speeds in each flap position.
You could use the Cortex Bank 1 and Bank 2 settings if you wanted to separately fine tune the flaps up gain settings in each axis separate from the full flap settings.
Now the little L-39 is really solid and 'locked in'.
Paul
I do not select gyro gain on gear position, but rather use flap setting (Flight Mode) as the flap position determines the speed range to fly, not the gear position.
The other week I took my laptop with me and fine tuned the Cortex in the little Savex L-39. Roll would be the first axis to enter an oscillation, and over the course of 3 flights I managed to dial down the roll axis internal gain and turn up the gain on the pitch and yaw axes. I reached the stage that I have the pitch and yaw axes turned up the maximum allowed internal gain. With full flap and the Tx gain set to 100% I still can't get it to oscillate in either pitch or yaw axis. The roll axis is turned down so that at 100% Tx gain it won't oscillate either. I reached these settings with full flap selected, and then just dialed back the overall Tx gain for mid flap and flaps up to be oscillation free at the highest speeds in each flap position.
You could use the Cortex Bank 1 and Bank 2 settings if you wanted to separately fine tune the flaps up gain settings in each axis separate from the full flap settings.
Now the little L-39 is really solid and 'locked in'.
Paul
Last edited by JSF-TC; 11-30-2020 at 08:51 AM.
11-30-2020, 09:08 AM
#8
[QUOTE=JSF-TC;12647540]On both my Cortex (Savex L-39 and DerJet Hunter) and Cortex Pro (Ultra Flash) equipped models, I am around 30% Tx gain flaps up, 60% flaps mid (take off) and 100% full flaps.
I do not select gyro gain on gear position, but rather use flap setting (Flight Mode) as the flap position determines the speed range to fly, not the gear position.
The other week I took my laptop with me and fine tuned the Cortex in the little Savex L-39. Roll would be the first axis to enter an oscillation, and over the course of 3 flights I managed to dial down the roll axis internal gain and turn up the gain on the pitch and yaw axes. I reached the stage that I have the pitch and yaw axes turned up the maximum allowed internal gain. With full flap and the Tx gain set to 100% I still can't get it to oscillate in either pitch or yaw axis. The roll axis is turned down so that at 100% Tx gain it won't oscillate either. I reached these settings with full flap selected, and then just dialed back the overall Tx gain for mid flap and flaps up to be oscillation free at the highest speeds in each flap position.
You could use the Cortex Bank 1 and Bank 2 settings if you wanted to separately fine tune the flaps up gain settings in each axis separate from the full flap settings.
Now the little L-39 is really solid and 'locked in'.
Paul[/
I do not select gyro gain on gear position, but rather use flap setting (Flight Mode) as the flap position determines the speed range to fly, not the gear position.
The other week I took my laptop with me and fine tuned the Cortex in the little Savex L-39. Roll would be the first axis to enter an oscillation, and over the course of 3 flights I managed to dial down the roll axis internal gain and turn up the gain on the pitch and yaw axes. I reached the stage that I have the pitch and yaw axes turned up the maximum allowed internal gain. With full flap and the Tx gain set to 100% I still can't get it to oscillate in either pitch or yaw axis. The roll axis is turned down so that at 100% Tx gain it won't oscillate either. I reached these settings with full flap selected, and then just dialed back the overall Tx gain for mid flap and flaps up to be oscillation free at the highest speeds in each flap position.
You could use the Cortex Bank 1 and Bank 2 settings if you wanted to separately fine tune the flaps up gain settings in each axis separate from the full flap settings.
Now the little L-39 is really solid and 'locked in'.
Paul[/
11-30-2020, 09:19 AM
#9
It just dawned on me I've never actually set differing gain values based on flight modes, and to be honest I don't do much gyro tuning at all. I have a habit of picking a number to start, typically about 25% or so on all axes, fly it, as long as it doesn't do anything bad I leave it alone. So several of my planes could probably stand to have the gain increased, and possibly increased further yet for landing mode. Might have to make it a goal to do this soon.
11-30-2020, 09:35 AM
#10
My Feedback: (2)
15-25% should be max on gyro gains, especially if your doing high speed runs and just want one setting, yes depends on the the jet but anything more than that your nearly guaranteed to see flutter. I've seen some people who have higher gains but only for landings.
11-30-2020, 09:51 AM
#11
Just wondering what's the typical difference in gain values. I realize that every application is different, so I'm just looking for a ball park number.
I've dialed in my gain for normal flying and am looking for a plug number to increase it when my retracts are down. This is just a starting point and I'll fine tune it from there. I was thinking that about +10 would be a good starting point, however in speaking to a friend at the field he's adding about 40, which seems excessive.
Yes, I know I could put it on a dial but I prefer to start with a best guess number and fine tune it using a trim tab.
I've dialed in my gain for normal flying and am looking for a plug number to increase it when my retracts are down. This is just a starting point and I'll fine tune it from there. I was thinking that about +10 would be a good starting point, however in speaking to a friend at the field he's adding about 40, which seems excessive.
Yes, I know I could put it on a dial but I prefer to start with a best guess number and fine tune it using a trim tab.
Or you could start at the same rate and use the trim option to increment from there.
Last edited by skunkwurk; 11-30-2020 at 09:55 AM.
11-30-2020, 02:33 PM
#12
Lots of good input here. Thanks, guys.
I didn't want to spend an inordinate amount of time fine tuning the gyro. Even if it's not optimized it's a lot better than no gyro. I have an iGyro 3e in one plane and a Spektrum AS3000 in another. Based on everything I've read I've programed the following:
- Start with a best guess number of 25 and fine tune it using a trim tab set to about +/- 10 range
- Set roll/pitch/yaw to 80/90/100%. That way, for example, if gain is set to 30 then I have 24/27/30 for roll/pitch/yaw.
- Cut expo in half when the gyro is on. Typically I'll have 20 - 40 expo, so it goes to 10 - 20 with gyro on. I can feel the difference when moving the sticks.
- Add 10 to the gain for low speed (take off and landing).
Using flaps to initiate low speed gains makes sense. I'll have to try that. I'm just starting to use gyros and won't be able do do much more until spring. I appreciate any comments or advise.
Joe
I didn't want to spend an inordinate amount of time fine tuning the gyro. Even if it's not optimized it's a lot better than no gyro. I have an iGyro 3e in one plane and a Spektrum AS3000 in another. Based on everything I've read I've programed the following:
- Start with a best guess number of 25 and fine tune it using a trim tab set to about +/- 10 range
- Set roll/pitch/yaw to 80/90/100%. That way, for example, if gain is set to 30 then I have 24/27/30 for roll/pitch/yaw.
- Cut expo in half when the gyro is on. Typically I'll have 20 - 40 expo, so it goes to 10 - 20 with gyro on. I can feel the difference when moving the sticks.
- Add 10 to the gain for low speed (take off and landing).
Using flaps to initiate low speed gains makes sense. I'll have to try that. I'm just starting to use gyros and won't be able do do much more until spring. I appreciate any comments or advise.
Joe
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Canadian Man (12-01-2020)
12-02-2020, 09:50 AM
#18
Sure.
Electronic gain = the amount of movement the servo outputs for a given sensor input. So if you double the gain it moves twice as much for a given rotation on that sensor axis (its probably algorithmic versus linear but you get the idea)
So yes, the servos will work harder and consume more battery with higher gain. How much? Eh, probably not a LOT but the true answer to your question is yes.
Now....there's also what I call mechanical gain.
Things that affect a gyro performance where if you have more mechanical gain you need or can only get away with less electronic gain. Example here is airspeed over a surface, the faster you go the more efficient the surface so the gyro needs less electronic gain at higher speeds than lower.
Increase the control surface size (think 3d planes) is the same thing, the huge surfaces need and tolerate less gain because they are so much bigger than a jet BUT they are generally moving at lower speeds.
Servo arm length, servo speed etc all affect it to a lesser extent.
So when someone says "how much gain are you running in a Rebel Pro?" the answer could vary greatly and all be correct depending on setup and flying style.
Electronic gain = the amount of movement the servo outputs for a given sensor input. So if you double the gain it moves twice as much for a given rotation on that sensor axis (its probably algorithmic versus linear but you get the idea)
So yes, the servos will work harder and consume more battery with higher gain. How much? Eh, probably not a LOT but the true answer to your question is yes.
Now....there's also what I call mechanical gain.
Things that affect a gyro performance where if you have more mechanical gain you need or can only get away with less electronic gain. Example here is airspeed over a surface, the faster you go the more efficient the surface so the gyro needs less electronic gain at higher speeds than lower.
Increase the control surface size (think 3d planes) is the same thing, the huge surfaces need and tolerate less gain because they are so much bigger than a jet BUT they are generally moving at lower speeds.
Servo arm length, servo speed etc all affect it to a lesser extent.
So when someone says "how much gain are you running in a Rebel Pro?" the answer could vary greatly and all be correct depending on setup and flying style.
