Hi all,

After reading and rereading both manuals it is not clear to me if Revolution mixing is allowed or required when the gyro is in the normal mode (not AVCS mode).

Anyone know the answer?

Ace

Don't need it. Most of us don't use rate mode for anything more than mechanical trimming in any case.

Can you use it? Yes.

This is something i've not quite understood. I've seen alot of pro pilots say they don't bother with rate even for setting the helicopter up mechanically.

At anyrate, if you are flying in rate mode, some kind of revo mixing is nescesary is it not? The tail won't hold otherwise? Or am I missing something here. They don't tell you to use revo mixing in the manual, even for setting the helicopter up mechanically.

I think there have been posts that would claim that it is better to fly with no gyro at all but I obviously did not choose that route.

I am concerned about a gyro failure in flight as remote as that scenario might be. So I would like to have a flight control that doesn’t use heading hold (AVCS mode). Whether I will be able to react fast enough to turn the AVCS mode off in a panic is another issue. As Credence has already stated, doesn’t it make sense to have some revolution mixing if you are NOT in the AVCS mode?

The Eclipse also has Rudder to throttle mixing function and I assume it would be beneficial to set this up when the gyro is NOT in AVCS mode. Is this a correct assumption? While practicing hovering on the SIM one of oddities that I experienced was a change in elevation without touching the throttle stick. It is still not known to me why this occurs.

Ace

Credence. Let me ask you this. If you just wing it with your setup, and in HH mode the servo ends up off center to hold a hover at say 15 degree's left, do you think you are helping your servo and setup or would it be better for it to be set to zero to hold in a hover? Take the time to do the mechanical trim and your servo will be happier, you will get better peformance and your servo will last longer.


Ace I've set up a buncha helicopters, from no gyro to avcs. Everyone I set up, once you get the tail stable in rate mode you can fly it around without the tail kicking around w/o revo mix. You probably can't punch or chop the throttle but I dont try it.

After that set it to HH mode and forget it. You dont have to worry about heading hold mode failing in flight. Either the gyro or the servo is going to go or its not. In either case it will be over before you have time to pucker your butt cheeks.

Throttle to rudder mixing or REVO is all the same thing. An attempt at mechanical or electronic mixing to automatically ofset torque by giving more or less tail rotor pitch when the power setting is changed.

As to your sim dilema, if you have wind turned on, a rotor system is more efficent with wind blowing over it then not. If you catch a gust or turn into the wind the heli will gain lift and go up, if you turn down wind, or compensate for a gust then the wind slows down or stops, the heli wants to drop until you get the power back on.

So, just for a basic hover you should be able to do it in rate mode without any sort of revo mixing. I take it this means that you'll need to manually control the tail untill you bring the rotors up to speed and get off the ground, is this correct?

I know, that ideally, all your controls should be at dead neutrals (servo as close to a straight 90 degree with the tail lever as possible). However, in my case, a 90 degree tail lever does not end up with the tail pitch slider at the very center of it's full range of movement, but ends up with it being a bit closer to the tail casing. This, obviously, can cause problems, because you'll get binding going one way, and none going the other way, and if you use the gyros limit function, you limit the travel going one way. This may just be a design problem on my helicopter, at any rate, to get a true neutral on the tail pitch slider the tail lever has to be offset a bit from the neutral servo horn.

Yes that is correct you do have to keep after the tail. In a true rate gyro, revo is great but as far as setting up for flying rate mode with a HH gyro, why pay the extra money for a 401 that your going to run in rate mode. The only real exception to this is some of the scale guys prefer rate mode for a more scale flying look but truthfully it forces you to learn to fly the tail and you'll be a better pilot, fixed wing included by learning to use the rudder.

There are those that prefer symetrical pitch throw setup but in reality, with the 401 its best (IMO) to center the servo at hover pitch, set throw with the limit pot on the gyro so that there is no binding in either direction. Seems weird but..........when going right your fighting torque so you need more throw. When going left your just taking enough pitch out to let torque do the work for you. If you set it up this way you won't have symetrical throw but you'll have symetrical piro rates.

That makes sense. So it comes down to a matter of preference then. At the moment i've got the pitch slider centered and the servo at neutral.

Thats true. If you look at the setup on most of the big boys, they run 611 or 601 gyros that allow setting both end points but they run with the servo centered at hover pitch. Thats the best of both worlds. When the do piro's with the torque, they are pushing plus using the torque and you can barely keep up it spins so fast. The best compromise for the 401 is the offset setup with the servo at 90 degrees at hover. Some tail designs are setup for symetrical throw either side of "neautral" some aren't it depends on your heli.

What are you flying?

Here's some reading if you want to dig into it a little.

http://www.futaba-rc.com/team/team-tip-002.html
http://www.ronlund.com/tr_setup.htm
http://www.raptortechnique.com/gyroconfusion.htm

Ace I've set up a buncha helicopters, from no gyro to avcs. Everyone I set up, once you get the tail stable in rate mode you can fly it around without the tail kicking around w/o revo mix. You probably can't punch or chop the throttle but I dont try it.

The literature that I have read indicates that transmitter mixes are more important with gas helis vs. glow. I would assume it has more to do with size and weight rather than fuel.
After that set it to HH mode and forget it. You dont have to worry about heading hold mode failing in flight. Either the gyro or the servo is going to go or its not. In either case it will be over before you have time to pucker your butt cheeks.

That might depend on elevation when the failure occurs. If the failure occurred at 100 ft for instance, I would have to flick two switches at most, one to turn on copilot and maybe one more to commence normal flight mode which can turn off HH. And then hope for the best because it is sure to spiral to the ground. I have to say that I have never experienced a servo failure (knock on wood) and I use that cheap Hitec brand exclusively. The failure is most likely to come from the gyro because of some outside influence like vibration or rf interference or an actual system failure. Because the gyro is outside the transmitter / receiver interface, failsafe can not be call upon for rf interference. So my copilot will not save me automatically. I have to have enough wits to turn it on and deactivate the gyro.

Throttle to rudder mixing or REVO is all the same thing. An attempt at mechanical or electronic mixing to automatically ofset torque by giving more or less tail rotor pitch when the power setting is changed.

Ah, you got it backwards. It’s rudder to throttle mixing and it is not the same thing as REVO. R>T mixing is used to compensate for the loss of power (not torque) from the main rotor when the tail consumes power in a pirouette, specifically in a hover.

As to your sim dilema, if you have wind turned on, a rotor system is more efficent with wind blowing over it then not. If you catch a gust or turn into the wind the heli will gain lift and go up, if you turn down wind, or compensate for a gust then the wind slows down or stops, the heli wants to drop until you get the power back on.

Hey, this could be another reason for oscillations in elevations while hovering if the gyro is set in HH and there are changes in wind currants. The transmitter is divorced from the gyro control when it compensates for wind gust. So even though you may have R>T mixing to compensate for power loss at the main rotor it is not in affect because the stick doesn’t moved. That would mean that if the gyro was fighting a cross wind while you were hovering and the wind all of a sudden slowed down, power would decrease at the tail and instantly increase at the main rotor causing the heli to puff up. Now think about the opposite affect (scary huh?). What is more interesting is that this scenario is the opposite affect of the increase in lift concept with an increase of wind velocity on the main rotor blades. I wonder which one wins. My bet is on the loss of power because of the tail rotor.

Now those that fly bear back (no gyro) will not experience this behavior because the tail will just weather vain and not rob any power from the main rotor system. My conclusion to all this is that cranking that gyro gain up to get a rock solid tail doesn’t come without some negative effects when you are trying to land. And maybe it is not a bad idea to switch to rate mode when you enter your landing sequence. It wouldn’t eliminate the effect but it should dampen it some.

Something to think about…

Ace

Some points to ponder.

Unless your doing fast piro's the power robbed by the tail isn't very signifigant. Same with your landing sequence. Your right though, I read that backwards. So its not a bad idea but at hover and around it you won't get much mixing going on.

Also your rudder servo is hooked to the gyro and the gyro to the reciever no matter what mode your in, hh or rate so a gyro failure is going to be the same either way. Trust me, when it happens it will be over before you realize it.

Flicking more switches than you need during flight is a bad idea.

I've never flown a gas heli, just nitro, electric and full scale.

I'm flying a mid size electric Eco-8 (it's about a .30 size). I guess it doesn't have a symmetrical tail then. Being able to set endpoints in each direction on the gyro would be real usefull though . I suppose doing it on the transmitter would be a bad idea huh?

I am sure you are absolutely right about being able to handle switches in a panic but I wanted to feel better about having an escape route.

Just so I totally understand the intricacies about this gyro I have copied the following text out of the GY401 manual.

Relationship between transmitter sensitivity
adjustment and gyro operation sensitivity
and operation mode
The gyro sensitivity becomes zero when the transmitter sensitivity
switching signal is in the neutral position.

This says to me that I can basically turn the gyro function off but still have rudder stick control. So if the gyro was experiencing rf interference which would appear as a failure, there is still one outside chance of saving the ship, unlikely as it might be.

For sh$ts and giggles I am going to try this with my transmitter to see if this idea is true.

Ace

You can set the sensitivty to zero BUT the gyro is still between the rx and the servo so the gyro is still driving the servo, not the rx.

Do what you like, but when you start flying you will see the difference between book knowlege and experiance.


Crede...setting the endpoints on the tx with a gyro like the 401 won't do you any good. The end points on the tx only control the piro rate on the rudder channel and gyro gain on the gyro channel.

The csm gyros have a setup routine that lets you set both throws as well.