How to stabilize vertical movement?

[guyguerra]

I have installed many BD3SX's, but am not happy with the one I just installed. It came off one of my other Helis and works fine. I installed it on a small Gaui X3. The problem is that I am chasing it vertically. It'll drop like 10 feet causing me to put in a lot of up collective, then it runs up, causing me to have to apply a lot of down. Sometimes it gets so close to the ground that it almost hits. I have reset the demon several times and increased the collective angle to 13 1/2 hoping it would become more sensitive. It's like the Expo is set, which it's not. I need to increase the agility I believe, but can't see how to do it.
Headspeed 2600
Pitch 13 1/2
Servos MKS 95's
Blades are correct size Switch blades
No extra weight
Using Jeti radio
Anyone have an idea?

[danfornow1]

I'm not the smartest guy in the room but this really doesn't sound like a FBL (BD3SX) issue. It sounds more like esc or rpm's acting funny. The only time the FBL is giving collective movements would be during rescue. Are you able to hear any RPM changes while this is happening. Are you using a governor, I would look in that direction.

[jchbarnes]

Maybe I've misunderstood what you're describing but this sounds more like too much play somewhere between the cyclic servos and the blades.

[Grittner]

whats your Throttle curve %...
maybe you have +100 0 +100 as a "V" curve, so when you are at mid stick you loose all speed or you mid point on a "V" curve is too low.
or the Throttle is not calibrate correct, what ESC are you using?

my guess is a rung throttle curve and not calibrate...

This FBL does not intervine with the RPM since it does not have a GOV, so definitely is ether the ESC or rung TX configuration on Curves.

[rhodesengr]

Does it act that way in forward flight or just hovering or just hovering close to the ground. Sounds like what my indoor coax does, drop suddenly in its own downdraft. Forward flight would keep your blades in clean air. Definitely not an FBL issue.

[guyguerra]

I agree that it's not in the demon. I thought it was slow on the servo correction, but I ruled that out yesterday. I increased the headspeed to 2670. If I go above that I enter the orange zone on the Castle ESC. I'm not sure the governor is working, even though it looks good in the software. I am pretty sure the problem is in the governor so I'll take a fresh look at it today. The problem is that I've gone through the soffetware twice already, and I bought this from a best buddy of mine and have seen it fly with no problems. The only thing I did was change from a Spektrum FBL to the BD3SX. First thing will be to exaggerate the governor settings to be positive it's working. Thanks to all of you for your suggestions.

[Dogdipstick]

Perhaps try to change the servo arms to a shorter hole ( closer to center) to increase the collective travel slider in the software to increase the resolution of the controller. Are you using " sinus linerization? "

[john2kx]

I had what sounds like the exact thing happen to me last month.

I use the Jeti ds16 Tx as well and read about the sticking throttle/gimbal ball not being perfectly round thread and made the decision to make some adjustments vs doing any type of material removal or lubricant. I loosened the set screw for throttle gimbal and eliminated the sticky feeling.

Made several flights with my glider and a few uneventful heli flights. Then, while in a hover with my raptor 720e, it dropped 10 feet and almost hit the ground. I tried it one more time with the same results. I am a thumb flier and did not realize that while I hover I would actually remove my thumb from the collective gimbal at times. Probably in a attempt to hold a rock steady hover vs letting my thumb feed in unnecessary commands.

The issue was finally realized while doing some bench testing. I had the gimbal tension so loose that it would drop a 1/4" or so when thumb pressure was released. Weird that I did not pick up on this while flying. It really did feel like a glitch or lost signal issue.

Hopefully, this is the case for you.