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Old Oct 21, 2012, 11:26 PM
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United States, FL, Fort White
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Help!
HK401b slow rudder in HH

When I adjust the gain on hk401b over 51% I lose rudder response. I mean under 51% I can piro just fine. Over 51% and the rudder will turn the heli but slow as mollasses in January. I can't find anyone else with this problem. Is it the gyro?
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Old Oct 21, 2012, 11:31 PM
Mr T
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New Zealand, Manawatu-Wanganui, Feilding
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50% is zero gain. 1 to 49 is heading hold mode, 1% being most sensitive. 51 to 100 % is avcs mode 100 being most sensitive.
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Last edited by trub; Oct 22, 2012 at 02:35 AM.
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Old Oct 21, 2012, 11:33 PM
Mr T
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I usually fly at about 20% and have the rudder switch change it to 80% for 3d mode
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Old Oct 21, 2012, 11:47 PM
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If I go below 46% I get horrible tail wag. And even in the instructions over 50% they are calling HH for HK401. Now I am really confused. Heli flies great at 47.5% but was trying to fly in HH like I thought I was supposed to fly in.
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Old Oct 21, 2012, 11:48 PM
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Why do I lose tail control?
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Old Oct 22, 2012, 02:59 AM
Mr T
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I really dont know, sounds very strange. Id stick with what works, if its holding fine at 47.5% then stay there, but for the price of them it might be worth trying another. I put some hot glue around the board inside the case to hold it as it was vibrating freely inside the case for a start. I couldnt find any recent instructions for setting the gain levels, so am only going off what worked for me.
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Old Oct 22, 2012, 07:35 AM
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Thanks for your help. I had done the hot glue mod before installing it. But that is kind of what I wanted to hear, that it was weird. Now I don't feel so bad for not being able to figure it out. Problem is that it is ok at 47.5 for sport flying but if I pitch bounce it the tail will swing around. I hate that. Head speed is maxed. I'm not a 3d flyer yet but I can fly well enough to crank on it a little and I do not want the tail to wash out. If you don't have any more suggestions I guess I will take my Futaba gy401 off of my part deprived Hurricane 550 and put it on the gt450pro. Thanks again.
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Old Oct 22, 2012, 08:13 AM
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Originally Posted by trub View Post
50% is zero gain. 1 to 49 is heading hold mode, 1% being most sensitive. 51 to 100 % is avcs mode 100 being most sensitive.
HH is the same as AVCS, so I think you did a typo and mean rate mode instead of the latter.
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Old Oct 22, 2012, 11:24 AM
Mr T
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Originally Posted by V999D02 View Post
HH is the same as AVCS, so I think you did a typo and mean rate mode instead of the latter.
Ah correct thanks for clearing that up
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Old Oct 22, 2012, 11:38 AM
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What is the range of that setting? Does it go from 0 to 100 or does it go from -100 to +100?

Sounds like you're not understanding how to set the gain in heading hold mode. I would set it on 80 and back it down until the wagging stops. If you can't get it to wag at 90 or more, then you need to put a longer servo arm.

BTW, you can not test heading hold behavior on the bench - the helicopter must be in the air, flying.
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Old Oct 22, 2012, 09:22 PM
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So I put my Futaba gy401 on it and set the mechanical linkage so it would hold in rate mode. It still weathervaned a bit but was ok. I flip the switch to HH and it is solid as a rock just like I wanted but have same problem. Almost no rudder response in the air. On the ground I move the stick and the slider very slowly moves in the direction I push but its like in slow motion. I back down on the gain I get my rudder back but lose the hold. What the heck is going on? I had the gy401 on my 550 Hurricane and it was great. Took it off and put on GT450 Pro and no go. HK401b doing the same thing. Turn up the gain to get it to hold and lose tail authority. Turn it down to get the tail back and it won't hold. The only thing not consistant is the corona metal gear digital servo that I have on the 450. I am going to swap for the Futaba digital servo I have on 550 tonight and try again tomorrow. Unless someone has a better idea please!
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Old Oct 22, 2012, 09:27 PM
Mr T
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The good thing is you have eliminated the gyro. I cooked a bluebird servo in hh mode a while ago. Changed it to a standard spektrum servo (digital but not as fast) and worked fine then
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Old Oct 23, 2012, 12:11 PM
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Still same problem. I turn up the gain to stop the weathervaning and get a good hold I lose tail authority. I turn it down just enough to get the tail back I lose the hold. Now I know for sure my equipment is good so what else is there?
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Old Oct 23, 2012, 12:37 PM
Mr T
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New Zealand, Manawatu-Wanganui, Feilding
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So its not the servo, not the gyro.. How does the tail move when on the ground without the blades spinning? Does it still get close to the limits in hh mode? Have u tried disconnecting the gain channel and tuning the gyro manually see if it the same problem, eliminating the radio. Can u grab some video of the servo, and the servo moving the tail blades, when you wobble the tail showing that it is doing something at the blades. 47.5 is hardly any gain, you are pretty much flying without a gyro hence the tail drift when you pump the pitch. So the servo arm might be too long? Really hard without seeing the set up doing its thing.
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Old Oct 23, 2012, 12:39 PM
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Originally Posted by SNiPER2020 View Post
Still same problem. I turn up the gain to stop the weathervaning and get a good hold I lose tail authority. I turn it down just enough to get the tail back I lose the hold. Now I know for sure my equipment is good so what else is there?
What numbers are you using? I think you're crossing the HH/RateMode boundary without realizing it.

If your numbers go from 0 to 100, then 50 is "zero gain in both modes" and 51 is "2% gain in heading hold" and 52 is "4% gain in heading hold mode"

So, you should be up somewhere around 75, which is "50% gain in heading hold mode"

Are you saying you turned it up to "way over 50" and it wags, but when you back off till the wagging stops, you have no control? Please describe what is happening with each number. I think you're misunderstanding the meaning of the number range. Tell us what number you dialed in, and what the helicopter did with that number.
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