Forward and left drift

[DumbDawg]

I'm trying to get to a hands free hover, the goal anyway. I replaced everything with cnc and its very smooth but when I try to pick the bird up it wants to take off mostly forward and to the left. I have to add a fair amount of stick to get it to stop and then the problem is chasing it.

The swash looks level, don't have a leveler, but still looks very level. The flybar paddles are evenly spaced and look to be flat and even on both sides and the main blades track perfectly. So I'm wondering what I'm missing. It has to be something obvious I'm sure. Thats why I'm asking because its beyond me at present. If I tilt the swash to compensate then the swash looks obviously out of kilter.

What am I missing???

[shizack]

A level swash is the starting point for setting blade pitch and pitch range. Once these are set, it's on to flight trimming.

Since you're drifting forward and left, you should start by shortening the pitch servo (right rear) swash link one full turn.

Of course, now the swash won't be perfectly level anymore. It doesn't need to be for flight. I doubt that anybody has a perfectly level swash after mechanically trimming for level hover.

[Cougar429]

That's true. The level swash is the starting point for setting up your linkages and pitch range. That will give you a STATIC setup.

For DYNAMIC setup, only flight will tell. The tail will try to blow the heli in one direction just by the thrust of counterracting the main rotor torque. That is the biggest correction you will have to make. The forward and aft adjustment is definitely unique to each and is more a result of weight-and-balance that anything else.

If you pay close attention, the engineers design these fixes into the real ones. Some are subtle, but on the Jetranger you will see the main rotor mast leaning to the right and forward. The right tilt is to correct for the tail, just like you will have to do with the swashplate. The forward tilt is to allow less angular change betwen the main rotor and mast in high-speed flight.

[DumbDawg]

Ok.. Then what I'll do is to make adjustments to the swash a little at a time until I can get to where I'm aiming. So once I get it close as possible then I can trim it out with the Tx.

Question then. Should I be trimming this all up with or without the gyro in head hold??

[Cougar429]

Heading Hold does not correct for lateral movement, just tries to maintain the nose aimed in one direction, (mind you, that working correctly also requires the tail pitch mechanism to be set up properly).

What you are aiming for is the trims for your cyclic control- which commonly is opposite rudder and throttle-to be as close to center as possible. Unlike the tail, which can change with alterations of your PIT TRIM or HOV TRIM adjustments, (which change the rotor pitch/RPM curve), the cyclic should stay once you have it set up right.

Note: The trims will actually point in the direction you need to correct to. If the trims are forward and right for it to hover near neutral, you need to tilt the cyclic in that direction.

[zimatosa]

You should also check your C.G....Not only forward/backward but r.side/l.side. Just in case you have not done so this would be first before moving swash..

Z

[DumbDawg]

Cougar... you lost me there. I need to trim out in the directions it wants to move??? ie forward and to the left. Won't this make it worse??? Don't I want to go opposite this?

If this is the case then the trims I have tried to apply certainly haven't helped now have they!!!:arggg:

I have been playing with the cg stuff too lately. I have a 30A esc which is kinda big and I had it mounted under the front or the battery holder. I've now moved it to the right side (outside) of the frame and as far forward as it will go.

Keeping everything tight is probably a good thing too. When I assembled the head I missed locktiting the top most two tiny screws.... They were very loose, fortunately I caught them in tiime before spooling up and having something fly off. Nice reminder for me to check check and check again after I go thru my battery packs. I have tree so when I'm done I charge the bats and look over the bird. Trying to establish good habits cause I already have all the bad ones...:YeaBaby:

[jh1947]

Cougar... you lost me there. I need to trim out in the directions it wants to move??? ie forward and to the left. Won't this make it worse??? Don't I want to go opposite this?
If I'm doing a total rebuild, I find I can get the trim pretty darn close W/O ever getting off the ground, by placing the heli on a (really) smooth & level surface & spool up to just below lift-off, then systematically eliminate each drift component; e.g., if it slides left, note how much right aileron it needs to stop the drift. Shut the heli down, replicate the stick movement & watch the swash/servo movement, then adjust the servo links accordingly. Eventually it gets to the point where it will pretty much lift straight off, & then only need minor trim adjustments once airborne.
Note - The above strategy presupposes that the C.G. is correct.

[DumbDawg]

Excellent idea... I do that for the most part except for watching the servo movement and going opposite. I been winging it mostly... move a bit here.. try again, move a bit more... etc.

The cg is a toughie I'm finding. When my esc was under the forward part of the battery holder then ith my battery in the cg was really close. It would sit level when you picked up the heli.

Well I moved it to the right side and now it sits far enough back that the bird is now tail heavy even with the battery in it. Plus if I want the canopy back on... pphhtt!! forget it.. not enough room. BIGGER batteries thats what I need.

I'm going to move stuff agaaain and I'll watch the servo's too this time and see if I can't get this under control. Thx guyz

[jh1947]

....The cg is a toughie .... BIGGER batteries thats what I need....

Agreed, CG is a lot less problematic, when the battery weight is around 170 to 185 gm

[DumbDawg]

I noticed with my gyro, head hold, That when the switch is up the servo's respond immediately and then return to zero or their original centered position. With the switch down, stock Tx btw, then the servo will move and stay where I moved it to. Then it creeps back toward center sloooowly.

How do you set this up on a stock tx to stop the creep. I've seen Finless Bobs vids but he doesn't have any esky vids and the Tx's he uses are all futaba's and or programmable.

So how should this be set up??? I have it holding on rate with a very slow turn towards the right. but when I flip the switch it looses this and just spins out of control.

any ideas?