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wolfdad
12-14-2006, 11:45 AM
Ok, for some time now, I have been playing around with a Bergen turbine outfitted with an OF 4 blade head, Helitronix mixer, GY601 gyro, G3 receiver and all JR 8611 servos. Everything works beautifully as a unit and I have about 13 flights on her.

I have encountered one problem and it is driving me absolutely up the wall. Whenever a tail rotor or yaw input is made, the aircraft responds immediately, however the tail "hunts" or wags as it comes back to center. During the early flights, this was very un-nerving and, even now, it feels as if the tail wants to constantly let go. As I said, I am running a 601/9251 combination purchased new. Gain on the display is set, per JK, at 39 with limits at 110% and even on both sides. I had started out with the gain at 65 and, since the symptoms I am seeing indicate a gain problem, I have upped it all the way to 90 (transmitter only...have not messed with the 601 itself)with no appreciable change. Head speed is approximately 1250 to 1300 with Vblade 710's on the head and Vario 156mm tail rotor blades. This is no longer an issue of "are the tail rotor blades too small to counter the torque?" It is now me trying to solve this issue. I have made some incremental and small head speed changes with no difference. As I come out of a turn, it just feels like the aircraft is not going to steady up on the gyro and makes several passes over the hold heading. I can find absolutely nothing electrical or metal to metal that could be affecting the operation, so I figured that, after a year of playing around with this issue, maybe somebody has experienced the same thing.

Should anyone find that I left a parameter out or have a question, drop me a PM. I think I covered most of the bases, however I am sure that there is probably some small bit of info that I left out.

Ok, and help me out here.....no responses that my flying sucks....already know that and usually find something to blame it on, but not this time....this is a real issue.

Doc

cbergen
12-14-2006, 12:28 PM
FAI or 3D mode?

AVCS or normal mode?

Is tail Mechanically trimmed out?

wolfdad
12-14-2006, 01:28 PM
Chris,
I told you my mind was starting to take walks without me.

FAI mode and, I have the gyro page on the 14MZ where I am able to switch back and forth between normal and AVCS. Tail is beautifully trimmed and tracked. Gain, in the transmitter, is now set at 90 in AVCS, but no joy. Just wondering with the 4 blade head, if I ought to go back into set up and take the gain in the display unit higher than 39. Still learning with this 14MZ.
Doc

rkeith2
12-14-2006, 04:37 PM
Doc -

I recently reworked mine with the 9256 6 inches from the tail gearbox mounted at the horizontal fin with a much shorter control rod of course.

I made sure on the 14MZ that I was in normal mode and worked to a stationary hover adjustment and then repositioned my control horn to 90 degrees.

After that I found that with 150% both ways on the ATV Travel I could then adjust the GYRO screen to 34 AVCS and it matched the amplifier screen and works flawlessly.

Heli_jack
12-15-2006, 08:43 AM
Doc, Not sure what type of tail drive you have, I have noticed that flex drives have a tendency to do that, tho what I perceive is that this is a significant amount of hunt. How many wiggles? Does it settle down? What is the fuse?

Your 4 blade has nothing to do with it.

wolfdad
12-15-2006, 08:55 AM
Howdy Jack,
Hope all is well with you.

My Bergen 4 blade is a shaft drive and, other than this continueing tail issue, it has been really sweet.

Yes, I am sold on and using the flexi-drive in my BK and, yes, I might buy what you were saying, however no flex-drive here. Sherry reminded me last evening that it seems to be more prevalent and persistent "in ground effect." It is still there out of ground effect, but to a much lesser degree.
Doc

Peter Wales
12-15-2006, 09:16 AM
1250 on the head with 710's is a little slow. Try upping it to 1500 and see what that does. I run 1250 with 800's

wolfdad
12-15-2006, 09:31 AM
Peter,
You know we discussed this at Dalton and, when I got home, I raised the head speed and, unfortunately with no luck. For all the world, it looks like the danged gain needs to be cranked up.

Also, we got Mark home from the hospital two days before Thanksgiving. He is doing ok, but is very weak still. We were really lucky on this one.
Doc

Peter Wales
12-17-2006, 08:37 AM
I'm glad Mark is getting better, sometimes someone up there is keeping an eye out for you.

The first thing I would do with the heli is to pull the 4 blade head off it and put it back to stock. Just in case the extra inertia of the head is causing a problem. I cant see it being the cause but you seem to have tried everything else.

Also check the tailboom supports to ensure there can be no flex in the boom. It may pay to put the supports lower and wider if possible to make a good triangle. That should eliminate that. If you still have the problem, you may have some windup in the transmission, sticky pushrod to the tail or a faulty gyro/servo. Is the gyro firmly mounted to the chassis in a place where it wont "bounce"