Help with my gyro and flips!

[Sieze2]

When I flip the heli it comes back to the right way up, rotated with the nose about 20 degrees to the right? I have a 401 with 9650, and always run it in Heading hold mode. It holds really well all of the time, no tail wag etc. I am running a gain of 70. When ever the heli goes inverted the tail does not hold position .

The only thing I would say is my heli is a little bit heavier on the left (nearside). This is due to the tail servo, airleon servo, and wire bundel all being on the nearside of the heli. The COG is perfect front to back.

Any ideas how I can fix this problem?

Just to say, I am using all the tail slider range, and there is no binding in my tail pitch control shaft.

[jamiem]

sounds like a phasing problem. what heli is it?

[Sieze2]

sounds like a phasing problem. what heli is it?

Trex 450 SE v2.

(did'n captain Kirk have a phasing problem once )

[moyesboy]

As you flip its really hard to not move the rudder at all.
Try putting lots of expo in the rudder control and see if that makes a difference.

There may be some swing of the tail due to the torque changes. Try upping the gain and see if it will take it without wagging. That might improve things.

With the trex450SE there shouldn't be a significant phase error, and it is not easily adjustable. A phase error means the axis of rotation for aileron is not quite in line with the tail boom (and elevator is similarly displaced, remaining 90degrees to the aileron). however a phase error would mean it pointed off when inverted and then returned to the original heading when it got back to right way up.

Most likely suspect (Except pilot stick error) is ccpm interaction, when you move the collective you might be getting a bit of aileron, when you move the elevator you might be getting a bit of aileron due to errors in the way the servos move together.
Best place to find out about this is with finless bobs videos at helifreak.com. Basically first with zero collective pitch you must have all the servo output arms horizontal and all the mix arms horizontal. Then you adjust the end points of the individual channels to get the swash to move only how it is supposed to (one servo can move a bit more than the others and upset the mixing).

If you pull up vertical from fast forward flight (eg into a stall turn) does it pull off one way? similarly if you do a big loop is it straight? If it seems straight when you don't use as much elevator in these manoevres, but screws out on a tight flip on full elevator, then its probably ccpm interaction rather than phase error.

[Sieze2]

As you flip its really hard to not move the rudder at all.
Try putting lots of expo in the rudder control and see if that makes a difference.

There may be some swing of the tail due to the torque changes. Try upping the gain and see if it will take it without wagging. That might improve things.

With the trex450SE there shouldn't be a significant phase error, and it is not easily adjustable. A phase error means the axis of rotation for aileron is not quite in line with the tail boom (and elevator is similarly displaced, remaining 90degrees to the aileron). however a phase error would mean it pointed off when inverted and then returned to the original heading when it got back to right way up.

Most likely suspect (Except pilot stick error) is ccpm interaction, when you move the collective you might be getting a bit of aileron, when you move the elevator you might be getting a bit of aileron due to errors in the way the servos move together.
Best place to find out about this is with finless bobs videos at helifreak.com. Basically first with zero collective pitch you must have all the servo output arms horizontal and all the mix arms horizontal. Then you adjust the end points of the individual channels to get the swash to move only how it is supposed to (one servo can move a bit more than the others and upset the mixing).

If you pull up vertical from fast forward flight (eg into a stall turn) does it pull off one way? similarly if you do a big loop is it straight? If it seems straight when you don't use as much elevator in these manoevres, but screws out on a tight flip on full elevator, then its probably ccpm interaction rather than phase error.

I'll try upping the gain and see what that does. I am only running +9-9 pitch so didn't bother setting up for ccpm interactions as I figured the endpoints are not being used due to the reduced pitch range. I did initally try to setup for ccpm interactions, but when I set the bubble for 0 pitch, then up to +9 and back to zero, the bubble would not recenter. I fiured it was due to slop in the swash/head. I also found using the levelling bubbles unlevelled the flybar, making setup very difficult, so I gave up .

I haven't done any big loops yet. It does seem fine on stall turn though. When I give it max pitch from a hover the tail pulls a bit one side, but corrects itself, I though that was normal? Maybe it is just me inadvertantly adding some rudder while changing pitch levels?

[moyesboy]

On my 450 with 401/fs61bb I cannot see any tail swing on a full pitch climb out or pumping the pitch.
I suggest you try the more gain.
Also more head speed might help because more head speed means less pitch change and also more tail revs which makes the tail more powerful.
2200-2400 for wood blades. 2800 -3000+ for carbon blades - then the little rex really shows its stuff.

[Sieze2]

Thanks, Was just reading on helifreak that more head speed stops the tail jumping out on full pitch climbs.