Tail drifting in Idle Up

Tail drifting in Idle Up
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Tail drifting in Idle Up - 6/5/2006 4:19:50 PM

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From: Homerville, OH, USA
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I've got a Airskipper 50, with a Futaba 401 gyro, with matching servo. During normal flight mode, the tail is locked in. When I switch to Idle Up, the tail drifts to the left about 2-3 degrees per second. I used about 10 units of sub trim to fix the drifting, but after about 5-8 min. of flight in Idle up, the tail started to spin around about 3 times before I was able to get it down ( Luckily no damage). I went up to the heli, and noticed gyro's red light was blincking red.
I took the sub trim out, and decided to fly it just in normal mode, I powered in off, and then back on, the gyro's red light became solid. I flew it for about 5 min. before the tail started to swing back and forth about 20-30 degrees.
Does anyone know what might be causing this problem, and how to fix it.
Thanks

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Harry Wagner

RE: Tail drifting in Idle Up - 6/5/2006 4:25:49 PM

BarracudaHockey

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First off center your trim and sub trim.

On the bench turn on the receiver and watch the light, it should blink for 3 seconds them come on steady.

Move the throttle stick from idle to full and back and verify the light remains steady. While you are moving the throttle make sure not to move it side to side. If the light flashes in normal mode while moving the throttle find and inhibit REVO mixing (you didn't say what radio you are using)

If the above test passes flip to idle up. If the light starts blinking then you have different trim settings that are tied to your flight mode switch, find and set the rudder trim to 0 in all flight modes and start over. Also check do the throttle stick test to make sure you dont have revo enabled in idle up either.

Also verify your mounting tape is secure and that you are turning the gyro on and letting it boot to a solid light in HH mode before disturbing the helicopter. If you have the 9253 or 9254 servo also check that you have DS MODE ON on the little dip switches on top of the gyro.

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(in reply to harryw13)

RE: Tail drifting in Idle Up - 6/5/2006 5:21:51 PM

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From: Homerville, OH, USA
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Ok, the light stays steady when I move the throttle in normal mode. When I switch to Idle Up, the light starts to blink, and will not go steady. I'm using a JR 8103, there is only one sub trim for all flight modes, and the rudder trim now is 0. The Revo mix values are all 0, for all flight modes.
Anything else I can try?
Thanks

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Harry Wagner

(in reply to BarracudaHockey)

RE: Tail drifting in Idle Up - 6/5/2006 5:25:25 PM

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sounds like your radio set to the stunt trim option (the 8103 has this option) and has a different tail trim in stunt 1, set the trim the same in all stunt modes. if you have to change trim from one day to the next, set all modes the same and then you can reset the neutral point of the gyro with it on by flipping between norm and HH 3 times each with one second intervals and on the last flip leave it in HH, it'll reset the neutral input for the gyro and you can continue flying.

kc

EDIT: if you have a 'DT' (digital trim) this function is not in the menu but you'll have a different on screen trim in each flight mode. look on the screen and watch the tail trim as you change flight modes, you should be able to see the trim lights move if they are different in each mode.

< Message edited by KC36330 -- 6/5/2006 5:37:14 PM >

(in reply to BarracudaHockey)

RE: Tail drifting in Idle Up - 6/5/2006 6:26:40 PM

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From: Homerville, OH, USA
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I have the digital trim's, so there is no stunt trim function. I'm not sure I understand what your saying about the on screen trim light. The only other trim screen I have on the 8103 is the sub trim, and it does not change when I switch between flight modes. Right now the sub trim for the rudder is zero.
Thanks

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Harry Wagner

(in reply to KC36330)

RE: Tail drifting in Idle Up - 6/5/2006 7:20:30 PM

BarracudaHockey

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On the main flight screen, not the programming screen, there should be a numeric or bar indicator of the rudder trim position, go to each mode and center it.

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RE: Tail drifting in Idle Up - 6/5/2006 7:39:38 PM

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So that's what those bars on the screen are for. OK, now I've got a steady red in all flight modes.
Thanks for all your help.
Time to go fly.
Harry

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Harry Wagner

(in reply to BarracudaHockey)

RE: Tail drifting in Idle Up - 6/5/2006 7:46:46 PM

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figured that was the problem, glad you got it going.

kc

(in reply to harryw13)

RE: Tail drifting in Idle Up - 6/6/2006 12:11:15 AM

tippy

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quote:

ORIGINAL: barracudahockey

On the main flight screen, not the programming screen, there should be a numeric or bar indicator of the rudder trim position, go to each mode and center it.

I'd like to learn from this too. Is my thinking correct?

During initialization, the 401 (gyro) memorizes the servo signal from the TX and sets this as netural (in the gyro) at which time the light goes STEADY.

When a servo signal that doesn't match this "memorized" signal is received, the gyro light shows a double flash.

So, after the initialization/memorization process, if you find it necessary to tweek your rudder trim setting at the TX, the gyro will see this as a change of servo signal and displays the double flash until the signal changes back to the signal it memorized. The gyro will see this "change" of trim as a small stick input and in turn induce a slow YAW change (tail drift?).

If the "new" trim setting is the right trim setting, you must "command" the gyro to re-memorize the new setting:
Method 1: Power down the heli/gyro and power the heli/gyro back on again (in HH) to learn the "new" servo position.

Method2: If motor is running, land. Toggle between AVCS (HH) and Normal 3 times within a 1 second or less ... landing on AVCS at the end. This will "command" the gyro to re-memorize the new servo (neutral) position.

Does that sound right?

I fly mostly in Normal mode and almost always have to click the trim a beep after powering up. So if/when I go to HH, I need to do at least one of the re-memorization methods (after changing trim) before attempting HH flight ... right?

Good Luck,
d.tipton

(in reply to BarracudaHockey)

RE: Tail drifting in Idle Up - 6/6/2006 12:22:45 AM

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yeap, sounds exactly like how it works.

you can also force the gyro to center the servo by moving the stick back and forth quickly and then returning it to center.

kc

(in reply to tippy)

RE: Tail drifting in Idle Up - 6/6/2006 5:19:38 PM

BarracudaHockey

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You got it Tippy.

JR gyros like the 500t are preset to the center pulse width but for various reasons thats not always perfect, thats why you need to subtrim the drift out of them so that the transmitted center pulse matches what the gyro is looking for.

The 401 memorizes center, so yes, if you need to crank the trim over in normal mode and reset the gyro (power off or switch flipping) it finds the new value as center.

The best way really is to trim the tail linkage to get it as close as you can with the servo arm at 90 degrees and no trim, that way the gyro is operating in its most effective range. Remember that with the servo at center you are actually getting negative expo, that is more throw at center than the extremes due to the round servo arm being translated to linear motion. (on Futaba radios this is the same as adding positive expo to a control to make it more sensitive around center).

To farther this discussion and dispell a myth I keep hearing. Expo in the radio will not effect the gyro performance or make it mushy as some believe. Expo in the radio is only applying expo to what it sends out as a stick command, so if you move the stick half way w/o expo its sending a pulse that says move half way. If you crank a bunch of expo in and move the stick half way, the radio is performing a calculation based on how much expo you asked for and tells the rudder to move 1/4 of the way at 1/2 stick. The gyro simply interprets it as 1/4 stick movement, it doesnt know or care how far the stick actually moved.

So some people are lazy they just let heading hold do its thing even if the servo is 15 or 20 degrees off center to hold a hover but they arent doing themselves any favors.

How much difference this makes in the air may be the subject of some debate but I'm a bit retentive about how I set my helis up and those I build for other people.

< Message edited by barracudahockey -- 6/6/2006 5:29:45 PM >

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RE: Tail drifting in Idle Up - 6/12/2006 3:13:37 AM

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OK, I have now fixed the tail drifting problem, but now have another. About every 2 flights, the tail loses control, and starts to spin around. After I land the heli, I check the gyro (Futaba 401), and the light is steady red. I throttle her back up, and everything is fine again (staying low, in case it happend again). After about two perfect flights, it happens again. Anyone have any ideas? I have the gyro set at 95 percent, at the transmitter. I thought about getting carbon fiber tail rotor blades, I've heard that the gyro does'nt have to work as hard with them, could the gyro be getting overloaded and just quit for a couple of seconds?
Thanks

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Harry Wagner

(in reply to BarracudaHockey)

RE: Tail drifting in Idle Up - 6/12/2006 4:44:49 AM

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sounds like the tail fork is cracked and slipping, this is a very common problem with the plastic version. my R60 has a JR extreme heading lock gyro G5000T with the 8700g servo and it breaks the plastics regularly, just snapped 2 of them this weekend, I've got the aluminum to replace it with this time. I've been pretty lucky, I've broke at least a dozen or so of them and every time I'm able to give hard right tail and it'll shove it back on the brass and auto in, last one didn't make it to the runway and had to put it down in the grass, which for those who know me is an insult and I'd rather be hung then sit my bird in the grass

kc

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< Message edited by KC36330 -- 6/12/2006 5:05:19 AM >

(in reply to harryw13)

RE: Tail drifting in Idle Up - 6/12/2006 1:10:35 PM

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I checked out the tail assembly, and could not find anything cracked. I have a direct tail drive on the airskipper, which I think is different than the R60. If it was the tail fork, why would I be able to fly a couple more flights before it happened again?
Thanks

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Harry Wagner

(in reply to KC36330)

RE: Tail drifting in Idle Up - 6/12/2006 2:57:00 PM

BarracudaHockey

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Check your battery voltage under load, the 401 can get squirlley when the voltage drops off, right up into resetting in flight (trust me you don't want to find out about that)

Also when you say 95 percent are you talking about the gain? If so feel your servo when you land, I'll bet its getting hot, if so you are running to much gain. Only run as much gain as you need to hold the tail during fast sideways or backwards flight, any more and you are over working your servo.

Also where is the limit dial set at?

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RE: Tail drifting in Idle Up - 6/12/2006 4:27:13 PM