Marty Hall

My Feedback: (2)

I've been trying properly program my T8UAPS either in PPM or PCM to run a set of Futaba GYA351 and GYA352 gyros in a fixed wing aircraft and am running into problems. [:@]

The instructions have at least a few errors in them about the configuration of the Tx starting with the Gear Switch ( Switch E ) and what you can do with it. According to the instructions with the gyros, it is a three prosition switch but it's only a two. When I sub Switch G that is a three position, things just don't work properly in that the gyros ( when I get them both working at the same time ) are in AVCS in two positions and Normal in one. If I program as per the instructions on Switch E, I end up with Normal in one position and AVCS in the other with no Off. I've tried every combination I can think of and held my mouth in more positions that I ever thought posible and no joy.[]

Anybody ever been there, done that, and have the Tee shirt?[:-]

Thanks,
Marty Hall

Phil Cole

Switch C will operate channel 7 with three positions, with the centre position putting the channel in the middle of the range. channel 7 is used by the aileron differential program, so if you using that function, you can't control ch 7 from switch C.

The other thing you could is use offset mixes, activated by whichever switch you want. Go to a PMIX and cycle through the master channel selection until you get to OFS. When the offset mix is activated, it adds a fixed offset to the servo position. Use a servo temporarily plugged into the gain channel to get an offset close to the middle. Use other offsets (activated at different positions of your gyro gain switch) for the gain settings. This way, the three gains settings can be adjusted without affecting the others.

If you run out of PMIXs because you want them for other things, you will have to just use ATV to set the gain when the gyro is active, and then go back to the offset mix to make sure the zero setting is still zero.

Marty Hall

My Feedback: (2)

Been there.... only using switch G which is also a 3 position switch. No joy. When I get things set up as close as you can to the instructions, I have [Normal - AVCS - AVCS] and not [Normal - Off - AVCS]. When I set up using switch E as per the instructions I get [Normal - AVCS]. One thing I read some where talks about setting a positive and a negative setting at each step vs. the positive OR negative in the instructions.... I may try that. BTW, already using the OFS selection.

Thanks for your response.
Marty

Phil Cole

If the gain is very close to zero, then it doesn't matter what mode the gyro is in. I don't think they have an off setting as such.

You could use subtrim to trim the control channel with the switch in the middle so the gyro is just at the point of going into normal mode. This would give you the lowest gain setting. Or, adjust the subtrim for minimum respose at the servo when you rotate the gyro in your hand. I have not done this with the GYA series, but all the gyros I've tried can have the gain set low enough that they have no effect in flight.

Marty Hall

My Feedback: (2)

Some where I read if the gain is below 40 then it's Off. O.K....... now what to do with that bit of information?

Phil Cole

I just read the GYA 351 instructions. They say that if the gain control channel is sending a servo position less than 40% from centre then the gyro is off.

At 40%, the gyro is on, with the gain at 0. If the control channel is at 70%, the gyro gain is 50%. Whether the gyro is in normal or AVCS depends on the direction of the control channel.

If you want to be sure of what the control channel is doing, disconnect the gyro and plug in a servo. If the servo is in it's centre position when your gain switch is in the middle they gyro should be off according to the instructions. You can confirm this by plugging the control channel back into the gyro and rotating it. If the control surface(s) don't move is response to you moving the gyro about it is off, no matter what the light is doing.

If you set the control channel mix (or ATV) so the servo would be at 70% deflection when the switch is at one side or the other, then you will get a gyro gain of 50%. Plug the gyro back in, and the light will tell you which direction the servo has to move for AVCS mode.

If you can't get the servo to sit in the centre position when the switch is centred you have a problem with your mixes, or maybe you didn't ensure that the control knob for the channel is in the middle.

If you disable all the mixes, does the gyro behave the way you expect if you control the gain using the control knobs to set the gain? The gyro will be off with the knob in the middle. It will turn on with progressively more gain once you turn the knob CW past the 2 o'clock position or CCW past the 10 o'clock position.

I agree that the gyro instructions have the switches all wrong. Part of the problem is the American 8UA switch arrangement is different to the switch arrangements on 8Us in the rest of the world. Subbing G for should work as you intend.

Marty Hall

My Feedback: (2)

You're saying some things I haven't tried yet but suspected to be true. The switch thing is for sure. In the "rest of the world" is Ch 5 gear? There may be another difference. Your also saying to set other than one side at 70 and to have the knobs in the middle. The instructions say to turn them to 0. All things I have wondered about.........

You've given me food for thought..... Thanks.

Phil Cole

ch 5 is generally gear in Futaba systems. The rest of the world, and helicopter 8UHs in the US have the ch 5 switch on the right hand side, and the three position switch on the left.

Think of the knobs as having zero in the middle, -100 on the left, and +100 on the right. The little pictures in the GYA instruction sheet show the knobs in the middle.
If you had the knobs all the way to one side then that's almost certainly your problem.

Marty Hall

My Feedback: (2)

I'm at work and can't check but I'd just about bet you a tall cold one that the instructions say to turn it all the way to the left... or words to that effect. I questioned it and the guy helping me questioned it but we figured some one had to know more about what we were attempting to do to the knobs are all the way left. And yes... it does make more sense for them to be in the middle. Tonight they will be.

Phil Cole

Marty,

I hope RCU doesn't mangle this link too much. It's easier to read when you blow it up on the screen. I would have a hard time seeing all the little details they show on the printed version, particularly when I'm "wasting" good flying time try to read the thing.

http://www.futabarc.com/manuals/gya351-manual.pdf

Marty Hall

My Feedback: (2)

Your's look a bit clearer. Isn't strange....years ago print was much larger and sharper........ Mmmmm..... Maybe I owe you a tall cold one. When you going to be in Fairbanks, next?