stable hovering but not inverted?!

[crash-test-tomo]

Hi guys, iv finally got around to fixing all the little gremlins with my 450x so I can think about selling it, for some reason in a hover the heli sits pretty solid but in an inverted hover it needs almost constant down elevator to keep the tail from dropping??
The swash it as near to perfectly level as possible and blades a bang on 0 at center so Mechanically it should be pretty bang on. Is it something like cyclic gain I need to look into or is there something silly im missing?
Someone educate me please lol

[Crumpet]

Have you used transmitter trim to get it hovering properly?

This would be masking a problem and would make the problem twice as bad inverted.

Just an idea

[crash-test-tomo]

No mate no trim at all, isnt everything supposed to be at 0 with fbl

[tomatwalden]

have you checked the monitor screen on your TX to ensure it's not a calibration issue?

[dillwhacker]

How does down elevator keep the tail from dropping?

[tomatwalden]

How does down elevator keep the tail from dropping?

Nose-in inverted, down elevator will lift the tail ...

[dillwhacker]

Nose-in inverted, down elevator will lift the tail ...

Yep..

[crash-test-tomo]

I havnt checked the monitor to be honest but It hasnt been so long since I updated the tx (dx8) and calibrated it. I believe it was GIXERMAN that highlighted that issue a a few months ago.. Cheers brian lol
If that was the problem aswel though wouldnt it be the same whichever way up the heli is?
I remember I did decrease the headspeed before I cured the vibration so it could be a little better if I go back up abit... Maybe?

[Holst]

Could the fbl controller be loose or being pulled by wires when inverted?

[crash-test-tomo]

I dont think so no, its rock solid to be fair!

[tomatwalden]

OK, so thinking about this ... If the swash is level, and the TX is providing the correct inputs, the symptoms you are getting would be that the swash is remaining level with positive collective, but leaning forwards with negative collective.

That would make me look at the servos. Have you checked to see if the swash remains perfectly level throughout the collective range? Perhaps one servo travels fine in one direction but no so smoothly in the other.

Anyway, first thing I would do would be to put a swash leveller on it, and check for level travel from full negative to full positive.

[james_2k]

but surely the fbl unit should detect the uncommanded movement and correct accordingly. even with a swash which isnt quite level.

[tomatwalden]

but surely the fbl unit should detect the uncommanded movement and correct accordingly. even with a swash which isnt quite level.

I guess if the movement is slight but builds up, then it might not fall within the gain parameters..

Thinking about it, what are the pots set at on top of the BX?

[crash-test-tomo]

Yeah I did that last night tom, set the swash level with the tool and checked from full positive to full negative, fine. Then both ways again with full elevator and aileron in all directions and all servos run smooth to the limits.
The pots, 1 and 2 havnt been touched so are both straight and center, pot 3 which I believe is tail gain? Is set at a sort of 20 to 2 position.. Or 1.40 if that makes better sence lol

[Mike Sanders]

Originally Posted by tomatwalden
Nose-in inverted, down elevator will lift the tail ...
Yep..

I am sorry if I am a bit dim. I don't fly inverted yet but I was under the impression that, when inverted, applying down elevator will lower the tail and raise the nose. Am I wrong?

I have tried it on the sim but I can't keep it inverted for long enough to observe!