Hi guys..... I had a crash the other day, then I overspeeded the heli withouth blades and the tail belt overwarmed and I had to replace it, now I don't know what is happening, my t-rex's tail is wagging (goint left to right) very fast when I give some rudder to turn the nose (either left or right). I have a gy401 with 9650. it's very stable, I mean, the heli is straight all time, except when I give rudder, right after doing that, the tail starts wagging very fast (but not so open, maybe in 5cms) for maybe 3secs and then is stabilizes again.... what is it wrong?????? Thanks.

P.S. Each time I give some rudder, the light of the gyro starts flashing and then it stops, is it normal???? I have it in HH, 72% (it was working perfectly before)

you check the tail rudder assembly real good? make sure you didnt mess anything up in that area? make sure all the screws are still tight and nothing is missing/bent/broken?

edit: or have you tried putting the gyro into rate mode and see if it does the same thing?

Have you tried lowering the HH percentage?
Just my thoughts.

Hes just happy.

Try lowering the gain. 99% of the time, that's what it is.

Ok, I am gonna try next time. It just wags when I give some throttle, it wags maybe 3secs (not very strong though) before being centered again, it's not too bad. I read about decreasing the GAIN in the Tx, I have a DX7, I set it at 72% which is recommended for the GY401 in all the DX7. The thing is that it was working perfect, that is why I didn't want to touch the gain but I'll give it a try. If I do decrease... how much would be good???? Thanks.

in my copterx (same as trex) i use 45% gain and 40%HH, this is just what works for me.

What Tx are you using????? because I think the dx7 works different, I have to set more than 50% in order to be in HH, if I set less than 50% it will swith to normal mode. Anyone with DX7??????

I have the same set-up using JR XP9303. I have 65% gain on both ends works perfectly tail is rock solid. Also if you still have the tail wags make sure you don't have any binding on your links. Hope this helps.

I have the DX7 too with a GY401 gyro. At first I was at 72% gain in the gyro menu, as suggested by the video on the Finless section at helifreak. (it's not Finless, some other guy who made a video specific to the DX7).

So I had the gyro set to 72% in the DX7 menu, which is supposed to equal 32% HH gain for the GY401, but I think there is some misunderstanding about the DX7 value in the gyro menu and the real gain transmitted to the gy401.

Personnally, I had to lower the value in the DX7 menu to about 64 before the little tail wag would disappear. In my understanding, any value over 50 is HH mode, so there is a 2:1 ratio. 64 is 50+14 and 14x2 equals 28 gain for the real value transmitted to the gy401.

So I guess by setting my DX7 gyro menu to 64, I set a real gain value of 28 to my gy401. I dont know if I understand it well, at first I thought I was supposed to set the gain for the gy401 a lot higher than that, but it holds quite well that way and anyway, I get wag if I raise this value, so I'm keeping it this way.

Hope all of this helps a little.

Mat

In HH, the steady ON LED indicates that the rudder command from the TX is equal to the rudder command the gyro "learned" during initialization. Obviously, if the TX command is NOT the same as the "learned" command ... the LED will blink.

This is normal if: You are moving the rudder stick to fly the heli as long as when you recenter the stick ... the LED goes steady ON again.

This is not normal if: You center the rudder stick and it still blinks. This means that when you give a 0 YAW rate command (centered stick) ... the gyro will be getting a YAW rate command (tail will not hold). You can get this "centered" blink if you change the rudder trim setting AFTER the gyro has "learned" a different setting.

If for any reason, you need to change the rudder trim setting (AFTER gyro initialization), the gyro needs to re-learn the new setting (re-initialized or do the 3 mode change toggle step).
Since you have to power up the gyro in HH, this sequence needs to be followed:
*In HH mode, Power up/gyro initializes, learns the rudder command.
*Switch to RATE mode ... mechanically/electronically trim the heli.
*Switch to HH mode and re-init the gyro ... either by the 3 mode change toggle method or power off gyro and power back on.

Now ... in HH and stick centered, you should be trimmed and the gyro is providing 0 YAW rate control. Again ... if you have to click the trim after this ... you gotta do the re-init thing again.

Thanks guys, thanks magymat. I don't know how but the wagging decreased considerably.... I swear I didn't do anything, but now it's fine! It just wags very very slightly when I give rudder, I can fly easily with that, however, I'll decrease the gain if the problems persists after, at least I know that I can decrease it until 60% or so. For now it's acceptable. Thanks, that is my T-rex, it does some unexplicable stuff sometimes [:-]. Something else I don't understand and it has happened to me twice, after a hard crash the gyro reverses! when I try to spool up it spins and I gotta reverse the gyro from the heli and the Tx and then it's ok..... any explanation for that?????

About the steady light, then my gyro is ok, it's ON all time except when I give rudder (starts blinking) but after gets back to normal, but thanks for the clear explanation tippy, I didn't know anything about that.

Reversing the Rudder Channel (at the TX) affects the stick direction to nose response relationship only. So you would only need to reverse the Rudder Channel if the nose was turning opposite the stick direction. This is NOT to be determined while the heli is YAWing due to a reversed gyro. Check this on the bench in RATE mode. Move the stick right and see if the servo responds with the YAW nose right command. If this works ... you should never have to reverse the channel regardless of what the gyro is doing to your heli. Reversing the Rudder Channel has NO affect on fixing a reversed gyro.
Once you get the stick to nose direction relationship sorted ... you should NEVER have to reverse the Rudder Channel (assuming same equipment setup).

Reversing the gyro (at the gyro) changes the direction of the gyro ouput to the servo. This needs to be set correctly or the heli will YAW near uncontrollably. This can be checked prior to flight by simply YAWing the heli by hand and noting the response the gyro gives to the servo. YAW the heli nose left should produce a YAW nose right servo response. If not ... reversed the gyro ONLY.

I can't think of any reason why you would need to switch the gyro EVERYTIME before flight ... unless you are not allowing the gyro to init properly (ie moving the heli during gyro init or moving the rudder stick during gyro init or changing rudder trim AFTER gyro init) and the resulting non-functioning gyro response is "interpreted" as a reversed gyro condition.

I can't think of any reason to switch the rudder channel at the TX ... unless ...

Are you using a TX that has multiple model memories?? Are you using the same model memory each time??
Do you have more than one heli? Are you remembering to switch memories as you switch helis??

Thanks tippy. I am using DX7 and I have 2 helis, a raptor and a t-rex. Sure I always remember to switch of model.

Thanks for the explanation about reversing the gyro channel in the Tx. I wasn't sure because I remember I read in a forum that "each time you reverse the gyro in the gyro, you have to reverse the gyro channel".

About reversing my gyro in the gyro (gy401), It has been twice in 12 crashes (long historial, eh) that I try to spool up and the heli starts spinning (I always allow the gyro to initialize correctly, always), so what I do is to reverse the gyro in the gyro and voila! it woks great again, I have found it pretty weird though.

Thanks again

matador_24
I read that you had trouble with the light coming on, on your Rx (or taking along time to come on). I occasionally have the same fault, although i'm not sure if it is a fault, maybe i move the heli when plugging in and the system doesnt initialize correctly. Anyway i have noticed that if there is any problem when you plug the battery in, the gyro wont initialize properly and the light will remain blinking. With that being said i would advise to put your hand under the gyro and make sure the light is solid before spooling up.

Maybe for a specific type of gyro but not for the 401.

Still not the same thing (s) ...
Reversing the rudder channel (ch4 for Futaba), reversing gyro channel (ch5 for Futaba), and reversing the gyro response (at the gyro) are three different things.
You already know what the first and last does ...

Reversing the gyro channel (gyro gain) might only reverse which side of the "servo" command is HH or Rate mode... which might affect which switch position equates to Rate or HH mode. Never tried it before ... seems to have always worked fine without having to reverse the mode/gain channel