Looking for trimming help

[carlrai]

Currently have about 15 flights on a new TRex 450SA. Terrific little machine and having far more success with first steps of hovering and sliding it left and right than with a Blade CP. Following Finless Bob's set up videos played a huge part in the fact that I was hovering succesfully by the third pack. Two things remain to tweak for a more solid hover.

1. The nose drifts slowly to the right. Trim changes on the transmitter seem to help but eventually it returns. How do you determine if this is mechanical or a Gyro problem. I've reduced and increased gain and the problem remains so I doubt this is the problem. Any ideas out there?

2. At a throttle setting that yields a four to five foot hover, the control is very sensitive in that with just a thought of input it will quickly jump up or drop a foot or two. Any ideas as to how to approach which curve or combination of both will reduce the sensitivity at this throttle/pitch setting? More or less pitch? More or less throttle?

I'm having a ball with this little model and look forward to moving to a larger heli once I can master the basics of trimming and flying this one. Your input is appreciated.

Carl R.

[cholyoake]

what gyro are you using? if its a futaba 401, then it shouldnt be drifting. if it does drift the it probably initialized wrongly; moving the helicopter while the gyro is initializing causes the tail to drift, or you adjusted the trim before flying. if its a diffrent gyro i dont know what the problem could be.

what throttle/pitch curves are you using? also what pinion are you using on the motor? higher headspeeds will give more collective response making it more sensitive to moving up and down.

[carlrai]

Using th e 401 Gyro and it's still during power up until the LED is on. No trim adjustments before flying.

Throttle/Pitch are as per Bob's recommendations. Unfortunately, I'm not at home at the moment and can't confirm numbers exactly. I was looking for some general guide as to the approach to desensitize the collective. More or less pitch? Less throttle? etc.

I'm assuming you're suggesting a larger pinion?. Worth a try when I can get back to it.

Thanks for the response.

CR

[TheBum]

How far did you push the gain adjustments?

[carlrai]

15 each way

[WayneBrown]

Look up ErichF and get some one-on-one help with the bird.
He's a great guy and a pretty good pilot/mechanic. It WILL be worth your time.

[Seeker]

Using th e 401 Gyro and it's still during power up until the LED is on. No trim adjustments before flying.

Throttle/Pitch are as per Bob's recommendations. Unfortunately, I'm not at home at the moment and can't confirm numbers exactly. I was looking for some general guide as to the approach to desensitize the collective. More or less pitch? Less throttle? etc.

I'm assuming you're suggesting a larger pinion?. Worth a try when I can get back to it.

Thanks for the response.

CR

You should be able to put the gyro in non-HH mode and make sure the tail holds there with no trim. If it does not hold then, change the mechanical on the pushrod until it will in non-HH mode. Do this with no trim on the rudder channel. Also, if you have changed the trim on the Tx, recycle the power on the RX/Gyro after you re-center the trim.

[kgfly]

What radio ?

Regardless, check that there is zero rudder trim in ALL flight modes. Most radios have different trim memories for Normal, IdleUp and Hold.

Does you radio have hover pitch/throttle knobs or sliders ? If so disable them so they don't mess up your curves. AFAIK nobody uses them outside of precision hovering competitions.

Is your throttle/collective stick moving smoothly or on a ratchet ? If it has a ratchet then get rid of it, one click up or down is too coarse for flying a heli.

[Jermo]

1. Ken/Kgfly hit it. You have trim on on the rudder channel which is bad for the Gy401 (and totally un-necessary).

2. Setup your idle up mode to use a flat throttle curve like 95% or 100%. As soon as you are off the ground go from normal to idle up mode. When trying to hover in normal you're balancing a changing throttle curve AND a changing pitch curve. This is ok for taking off but for more consistent handling go ahead and goto idle up with a flat throttle curve. You'll find she hovers/flies more stable.

Double check you have throttle hold setup so that if you crash you can hit it to stop the motor. Do NOT slam the throttle down. In idle up (if properly set up) you have full negative pitch when the throttle is down and the motor still runs the same speed (typical setup).

You'll find you hover much more easily.

[Seeker]

1. Ken/Kgfly hit it. You have trim on on the rudder channel which is bad for the Gy401 (and totally un-necessary).

2. Setup your idle up mode to use a flat throttle curve like 95% or 100%. As soon as you are off the ground go from normal to idle up mode. When trying to hover in normal you're balancing a changing throttle curve AND a changing pitch curve. This is ok for taking off but for more consistent handling go ahead and goto idle up with a flat throttle curve. You'll find she hovers/flies more stable.

Double check you have throttle hold setup so that if you crash you can hit it to stop the motor. Do NOT slam the throttle down. In idle up (if properly set up) you have full negative pitch when the throttle is down and the motor still runs the same speed (typical setup).

You'll find you hover much more easily.

I'm not sure I'm a big fan of a new pilot hovering in idle-up mode. There's just too much to think about if something goes wrong. You can move up the throttle curve in normal mode to ensure you have enough headspeed.

I for sure agree to make sure you have throttle hold enabled.

Jermo, are you going to IRCHA?

My 2 cents :)

[carlrai]

Thanks for all the input. It's going to be a few days before I get home and have the opportunity to try a few of these approaches. Looking forward to it and will continue to post progress.

Thanks!!
Carl

[carlrai]

For what it's worth to any other newcomers, I was able to finally trim out this little irritating drift mechanically. After electronically trimming and resetting the gyro a number of times I was able to obtain a drift free hover. Once completed, I simply repositioned the tail servo to move the tail blades to the same position and set the trim back to center. The latter took a few tries as well but am progressing faster now that I have this little bug out of my heli.

Thanks again for all the input.

Carl

[swannking]

So, what did you do exactly to solve the problem. I seem to have the same problem although I think it is me pushing the rudder when I adjust the collectives.

[carlrai]

Determine if the problem is gyro or setup. Most likely it's going to be set up. Read Seeker's comments on previous page. Or just trim and recycle power. Repeat until it locks on then readjust the position of the tail servo duplicate the change made by the trim. Reset trim to center. Repeat until you're sick of it and do it some more. You'll get it and the result is a surprisingly stable tail. You'll be happy for the effort. If this doesn't work for you, start another thread with a complete list of symptoms and see what the rest of our world has to say.

CR

[carlrai]

There is another newbie thread listed above. Look in there for the tail rotor setup section. I think you'll find what you're looking for there

CR

[Jermo]

If the gyro/rudder is connected properly you don't need to adjust rate mode for hover. Although Futaba does suggest it. If you just center the slider in rate mode, set the limit on the gyro to prevent binding and run in HH mode it will hold without drift. It might wag or hunt but that's just a gain setting.

The point here guys is a drifting 401 is generally causing by trim or vibration.

edit: and going to a flat throtte curve using idle up mode makes the chopper more stable due to the flat throttle curve NOT higher headspeed. Higher headspeed does help but it's the flat curve that's key here.

[Skiddz]

IMO, once the new pilot gets over that "oh s**t slam the throttle closed" stuff, then flying in idleup is ok. At a minimum, I think newbies should learn to hover around 3/4 stick so they're used to the stick positions once they transition to idle up flight andset up their normal curve appropriately.

[Lastinch1]

For normal Mode IMHO Should be similar to the following, use your throttle hold feature!!

Governor mode disabled

Throttle curve
60% 65% 70% 75% 85%
Pitch curve
20-30% 40% 50% 65% 100%
Basically you want the middle of your curve to be near flat but not flattened out

If your swash is to sensative try decreasing the % in your swash set up to about +/- 50 %
If that ain't doing it try adding Expo to the tail and elevator and aileron about +20% if your using DX / JR
- 20% for Futaba