Rotor Disk Malfunction? I need help please!

[smasher77th]

I'm trying to fly my Golden Eagle 450 for the first time after 3 months since I purchased it. Even though it is supposed to be rtf, it wasn't. the swash was tilted like one of the dish network or Dirctv dishes, the tx was bad and had to be replaced, some servos were reversed in the mix and even after I got the new one, I had to blindly figure out how to program it on the PC. After so much guess work, and 3 months of on-the-job learning, I have finally set it up perfectly (ie: swash is level, servos operate in the right direction). but the swash is way up (about +5 degrees at 0 pitch, and +13 at 100% pitch, with subtrims at -120%. I had to reduce the swash connecting rods 15 full turns each, to bring the pitch to -5: 0: +5 for the aileron and the elevator, and -9:0:+9 for pitch and this is possible with the subtrims still at -45% for ch1, ch2 and ch6. All this time i've been doing this with the throttle cut switch on.
As I'm happy my work is come to an end, I turn off the trottle cut, and and armed with my RADD's instructions, I prepare my "flight school of 1' x 1' square, increase throttle to about 15 - 20%, and I notice something weird (Don't laugh at me, I'm just a curious newbie):

(Throttle is between 15% and 20% approximately)

1. At center stick, the rotor disk and the flybar disk are perfectly horizontal, and parallel to each other.
2. At forward stick, the flybar disk tilts toward 12 o'clock, but the rotor disk tilts toward 11:30 (approx)
3. At backward stick, the flybar disk tilts toward 6 o'clock, but the rotor disk tilts toward 5:30 (approx)
4. At left stick, the flybar disk tilts toward 9 o'clock, but the rotor disk tilts toward 8:30 (approx)
5. At right stick, the flybar disk tilts toward 3 o'clock, but the rotor disk tilts toward 2:30 (approx)
All linkeages and connecting rods are perfect, the swash tilts perfectly (hence the perfect tilting of the flybar) and the rotors are tracking perfectly, and have the same pitch.
At this point, I stop my training, and get so upset, and afraid to lose the heli like I did the belt cp before it (It crashed beyond repairs 5 seconds after I powered it on for the first time, without ever leaving the ground, because the throttle caught on a thread on my shirt and went to max power), I decide to throw away the stupid tx and rx, and get me a dx6i + an ar6100e, but today while practicing with RealFlight G3.5, I put my throttle at 15 - 20%, and noticed the same thing, but when I advance throttle to about 30%+, the rotor disk tilts appropriately (ie corresponds to where the flybar disk is tilting). I'm still getting the new tx (dx6i and ar6100e), but my question is this: is this normal, and can anyone explain it to me?
Since I can't increase throttle on my heli and do these experiments without it tipping over maybe, I decided to strap it to the floor with dog tapes securedly and then increase the throttle and see if it will tilt normally like it happened in the sim.
Any advice, suggestions or explanations as to why this is behaving this way, and if it is normal, will be appreciated.
Thanks for your help.

[JasonJ]

Unfortunately, you gotta fly it. Since you are so new, you should get someone who is experienced to fly it to ensure the helicopter is doing what it should for the control input given

[jeffk]

What you're observing is a result of a phenomenon called "gyroscopic precession". Because the rotor disk is spinning, it act like a gyroscope with regards to the direction it moves when force is applied. To get a rotor disk (and it's attached helicopter) to move in a particular direction, a force must be applied to the disk in a direction OTHER than where you'd logically expect to.

The whole subject is really beyond my full comprehension as of yet, but do some googling and you'll be able to better understand it.

[smasher77th]

Well, I strapped my heli on the table with insulation tape, and applied the throttle gradually toward mid-stick, while testing the stick fore/aft and left/right, and this is my observation: The more throttle I added, the more precise the tilting. At very low speed, for instance, the tilting is diagonal like I mentioned in my last post, but when the speed increases, the tilting is much closer to where I want it. I didn't have enough courage to cross 50% throttle, because the sound of my loving heli was mighty!

I think you're right, Jeffk!

After close examination, I'm tempted to believe that because the blades are rotating in a clockwise direction, the force (forward stick, for instance) is applied to the blade just after it crosses 9 o'clock, and that's where it starts tilting. and by the time it gets to 12 o'clock, it achieves the maximum tilt (as per stick imput) and because the power is not strong enough (low speed) the force is maximum around the location where the the tilt was first initialized, and diminishes due to lack of power (hence the 11:30 tilt), but when there's enough power, the force is maintained throughout the 'half disk' area, making the tilt precisely at 12 o'clock. At around 50%+ throttle, I noticed that the tilt was almost dead 12 o'clock, just like in RealFlight G3.5, which, by the way, shows me how accurate the sim is.

Thanks once again. It's amazing what one learns in the course of this hobby. I'm so loving it, even without having taken off for the first time. I'm sorry for those who call this machines toys.

Thanks once again.

[vera]

Yep, jeffk is right. If you don't have enough rpm to get enough gyroscopic precession then the tilt won't be as desired. Look at the head and notice that forward stick tilts the swasy forward, and forward tilt on the swash lowers the pitch on the blade/paddle at the 9 o'clock position on the heli. One would expect that this would tilt the rotor to the left, and it would do that if the head was turning slow enough. But at higher head speed gyroscopic precession kicks in and the reaction to the force at 9 o'clock is translated around the circle 90 degrees later to the 12 o'clock position. In flight you will experience heli wobble if the head speed is too low. Anyway, as jeffk indicates, I think your problem will be gone once you wind it up to the correct head speed.

On a different subject, if you ever encounter a problem of the disk being off by some amount when at the correct speed, it might be that the phasing is off. Some helis, like the Evo, have a clamp that holds guide pins which end up keeping the inner (rotating) part of the swash in phase with the blades. It's possible for that to be set wrong. It should be set such that when the blades are exactly crossways, or exactly nose/tail, the balls on the inner part of the swash are exactly crossways also. Otherwise the cyclic control will be off by some amount in all directions... as if the stick assembly was rotated on the tx by some amount. On other models it's pretty much impossible for this to get wrong because the guide pins come out of the head block.

[Skiddz]

RPM has very little to do with gyroscopic precession. In a nutshell:

If you apply an external force to a spinning object, that applied force is manifested approximately 90 degrees later in the direction of rotation from where the force was applied.

In our case, if you want the rotor disc to tilt forward, you would need to remove pitch (external force) at the 9 o'clock position (looking down from the top of the heli) and precession would provide greatest disc deflection at the 12 o'clock position.

Look at a main blade grip on your heli. Follow all the links down to the swash. See where that ball is in relation to the feathering axis of the blade?? There's your compensation for gyroscopic precession.

The OP is seeing this "oddity" because the heli is not in the air and reacting with the ground. The heli's mechs are designed to deal with precession and all we need to be concerned with is the proper tilt of the swash when we start churning the cyclic.