3gx tipping over and tail spinning

[malloryn]

Heli : 700N DFC standard kit with TT Redline 100 and Hitech optimat 7 reciever.

First issue
When doing the tilt check after power up the swash always returns to level when tilting i.e if I tilt the heli back the swash tilts forward and then back to level even though the heli is still tilted back. It's behaving like a rate hold gyro and not heading hold.
Is this normal operation?

Second issue
This could be related to me still getting the P/T curves setup and running in a new engine but..
On spool up the heli tilts to one side ( I think it's left ) and the tail spins when it's light on the skids.
I've checked the direction of the tail servo and it's ok.
I suspect the tail spin is due to too much pitch and too little head speed ( I'm running un-governed to set the 'no gov emergency' throttle curve) i.e too much torque and not enough headspeed on the tail to compensate.

The leaning over on take off I'm not sure about.

I've already had one minor crash luckily only a bent DFC bolt and bent elevator arms ( the blades, main and feather shaft got away with it).
Once repaired I'm going to put this on training gear as I'm not trusting it at the moment.

Note. All the DIR setup is done ( and redone after repairs) and is ok.

[moyesboy]

First issue
When doing the tilt check after power up the swash always returns to level when tilting i.e if I tilt the heli back the swash tilts forward and then back to level even though the heli is still tilted back. It's behaving like a rate hold gyro and not heading hold.
Is this normal operation?

Yes, the swash shuuld return slowly to level after you stop moving the heli. ITs not quite rate mode, it like heading hold with a shortened heading hold decay time.

Second issue
This could be related to me still getting the P/T curves setup and running in a new engine but..
On spool up the heli tilts to one side ( I think it's left ) and the tail spins when it's light on the skids.
I've checked the direction of the tail servo and it's ok.


there are two things, Gyro direction and stick response direction. Put the tail blades vertical, the bottom one is now like a boats rudder. Check when you move the stick it goes the right way (revese is on the tx rudder channel), check when you turn the heli the correction is to move it back to straight (direction is in the FLB controller).


I suspect the tail spin is due to too much pitch and too little head speed ( I'm running un-governed to set the 'no gov emergency' throttle curve) i.e too much torque and not enough headspeed on the tail to compensate.

The leaning over on take off I'm not sure about.
IF its left then thats the way the tail is pushing it...

I've already had one minor crash luckily only a bent DFC bolt and bent elevator arms ( the blades, main and feather shaft got away with it).
Once repaired I'm going to put this on training gear as I'm not trusting it at the moment.

Note. All the DIR setup is done ( and redone after repairs) and is ok.

Be sure not to touch the cyclic until the heli is off the ground - its a bit of a all or nothing jump into the air though!

[matjonze]

3gx tipping over and tail spinning

What version of the 3gx software are you using?

Are you using a governor in normal mode?

I found v1.2/2.1 to be very twitchy when lifting off, it really was a case of trying not to touch the cyclics until off the skids.

V3.0 is much better, once the pots are wound back.

I generally fly with the gov enabled in all flight modes and found that the heli is far more stable on the ground once the engine is on the gov and the headspeed has settled down.

I'm running linear pitch curves +\-13. My throttle curve is set to be 32% by roughly 1/4 stick to bring in the gov with normal mode, so it's quite steep.

You may find that training skids make the problem worse, they can create additional vibrations.

[coolice]

Hey.

The first issue is normal, in flight the swashplate would be held where it needs to be by the 3GX to keep the models fuselage where the pilot puts it.

With the second problem it could be a combination of things.
One of the first I'd check is that all gyros, tail included give opposite commands to whichever way you tilt or turn the mechanics. If the tail is spinning I'd check your tail gyro sense doesn't need reversing.

The tilting of the swashplate on take off could be due to your engine running rich while you run it in and in turn producing more vibrations through the airframe. These vibes get to the 3GX, or any FBL controller and give it a hard time as it does not know if the model itself is moving and it needs to correct the attitude of the aircraft. In this case it doesn't need to, but the vibes are causing the 3GX to input unneeded controls.

It can also be your engines cooling fan/hub assembly being out of balance, the fan is plastic and so can be out of shape.
Wheb the engine is idling do you feel or hear a buzzing through the airframe? A classic area where it shows up more is on the tail boom supports, some is ok but if it's severe enough these become a blur almost while the engine iscrunning.

What power supply are you running on the model to power the servos etc? Another area which can lead to problems with fbl machines, more apparent on the 3GX with the release of V3.
.