Hovering issue

[Westwind]

When I lift off into a low or high hover my e325 se will slide to the left for about 5 feet then right it's self and move to the right at an increasing speed. This happens without any input from me, total hands off. The gyro will hold the nose straight but the heli will still slip one side then the next. Same effect with the gyro turned off.
What could be causing this?

[Ruston]

Hovering issue

Have you flown any other collective pitch helis before? That sounds like perfectly normal behaviour. As you take off the tail rotor will tend to push the heli left, you need to correct for this with a little right cyclic input, it's the same for any heli with a clockwise rotating head. If it is drifting once in a stable hover then you should be able to trim it out, either by mechanically adjusting the linkages to the swash, using sub trim or just using the trims on the tx.

Not sure what you mean by turning off the gyro but the gyro is there to control the helicopter's motion in yaw so has nothing to do with the left and right movements.

[RcRotaryMadness]

As Ruston said really, Most helis have a clockwise rotating head and so most helis have a tendency to drift to the left on take off (close to the ground - look up ground effect). Once in a hover a good 6-10 ft up thats where you trim the heli to keep it as still as possible... although with the smaller helis they are never going to keep still for very long.

Also making sure theres the minimal amount of slop in the rotor head can help a lot too... goes a long way to making it easier to setup and fly!

[cjcj1949]

It is simple Physics. You have a horizontal force from the tail rotor to the left on and before take off. This will accelerate the heli to the left until you provide a balancing right force. You do this by tilting the rotor slightly to the right. It is not easy to get the balance correct. Lots of people don't know they are doing it, it becomes automatic. If you try the heli on a slippery surface it will move to the left on the ground. Some helis cheat by having a skewed undercarraige that tilts the heli right.

[barryorbik]

Its also worth checking that the three swash plate servo's are recentering every time and that their travel range is correct by monitoring the swash plate movements when you increase the pitch (with two motor wires disconnected to ensure it cannot start) to see if it stays level throughout its travel range, as I helped a club member recently who had some cheap (Tower Pro) servo's on a similar 450 sized helicopter and was having major problems controlling it.

To make the range and centrering tests easier, I temporarily changed the pitch setting in the Tx to -100, 50, 50, 50 ,+100 so anything approximating mid-stick would be 0 degrees of pitch and the top and bottom ends can be easily checked but dont forget to change them back to your original settings before you try to fly it again!!

Barry

[tomatwalden]

As other's have said, the left slip is normal. It's called Translating Tendency ...

Helicopter flying - Translating Tendency or Drift

T

[Westwind]

Re: Hovering issue

Hi guys thanks for your input, a little background on me. I'm a commercial helicopter pilot and aircraft mechanic so I do understand the physics. The issue is that the machine will lift up slip to the left (as expected) then with no input from me right it's self and slip to the right at an increasing speed. This is not something I have experienced or read about on real helis. Is this normal for rc helis.
How do you eliminate slop on the stock TT head? do you guys use shims?

[tomatwalden]

That sounds to me like the swash isn't moving level with collective input ...

The heli should only drift right if the swash it commanding it to go right. Although - thinking about it, if the heli is nose-heavy (have you checked CoG?), then would gyroscopic precession pull the right of the heli down?

For left drift to take effect, it must mean the swash is level at take-off collective pitch - perhaps the swash isn't remaining level as collective is increased?

Is this a flybarred or flybarless heli ?

[Westwind]

Re: Hovering issue

Also while in hover and I'm inputting right ruder, she will hold her ground for a bit then start moving to the right (no additional right input) one would expect, one balanced she should stay balanced. Note I'm flying indoors in a hangar, in ground effect and out.

[tomatwalden]

Is this normal for rc helis.
How do you eliminate slop on the stock TT head? do you guys use shims?

PS. no - not normal for RC helis.
Slop in heads is normally rectified with shims, although I'm not familiar with the TT heli.

[tomatwalden]

Also while in hover and I'm inputting right ruder, she will hold her ground for a bit then start moving to the right (no additional right input) one would expect, one balanced she should stay balanced. Note I'm flying indoors in a hangar, in ground effect and out.

Do you mean there's a delay in rudder input? If so, could be over-aggressive expo in the transmitter, or a deadband ?

[Westwind]

Re: Hovering issue

Thanks tom, this looks like someware to start. It's a fly bared heli. I don't think noise heavy CoG would have this effect as the blade pitch angles over the nose would not change

[tomatwalden]

Sure, nose heavy wouldn't change the blade pitch, but it would be a force pulling down on the front of the gyroscope (ie. the rotor disc). That force would react 90deg later - ie. the right-hand side of the heli.

On a flybarless heli, the FBL unit would compensate, but flybars can't, so I would guess that if particularly nose heavy, there would still be some roll-right effect of a nose-heavy heli.

[tomatwalden]

then again ... I might be completely wrong!

Another thought - do you have the gyro in Heading Hold, or Rate Mode ?

[mark_w]

So the only control you are inputting is rudder and throttle/pitch, and its moving the heli to the right and left by itself?

If so check for mix's in the TX and check that all the servo plugs are in the correct place. something does not seem correct.

maybe you could post a video of whats happening.

If you have the heli on the bench and move the rudder, does the swash move at all?