carfanatic

ok, this is my first heli and I"m slowly learning here, I have a question about the trims. When the heli takes off, should it naturally go in a certain direction? I"ve been doing radds school, but I"m just starting to go into the air and heli seems to go every where!! Just wondering if IT should stay some what still with minor stick imputs to hover.. I guess I just need to know the normal action to make sure everythings ok and I just need to work more at hovering obviously!

Prontow

I have experienced the same thing, I would SLOWLY increase rotor speed and the heli would go forward and to the left. This is my first heli also (Lots of learning to be done) I figured the uncontrollable sliding across the floor was normal and I needed more practice. I have leared two things since then- last week- ground effect causes a lot of control problems when the heli is a couple of inches off the floor and second is indeed practice. When I got up the nerve to throttle up a bit more and get a couple of feet in the air it calmed down a lot. I still wanders around a bit but as I get even more comfortable that will pass also. Can't wait until I can nose in hover.

Heli Bat

Ground Effect folks -- it will have a mind of its own in the ground effect. Ground Effect is basically Rotor air wash getting caught back up in to the blades again. Negative and positive airflow feedback. I think someone mentioned that you will expect and experience ground effect up to the hovering height that equals 1.5 times the width of total rotor width. So in this case, you can expect the Machine to wander and YOU have to control it more - with more input with the sticks from Ground ZERO up to about 24" off the ground. Someone else in here can do the math more if they want, I do not have my AXE in front of me and only guessing.

Heliko

Tail rotor drift doesn't help either. This happens when the heli is in a hover and forces are equal (lift=weight and thrust=drag) with the exception of tail rotor thrust. In the Axe's case T/R thrust pushes it to the left.

Turbulence can be another problem close to the ground. It causes all kinds of havoc as the air deflects off of irregular objects adjacent to the heli. A clear, level area will make hovering much easier.

IGE (In Ground Effect) hovering does have one redeeming quality because it requires less power for a heli to hover. This comes in handy on full size birds.
Hopefully this will explain some IGE/OGE differences. Ground effect increases lift when the heli is within about 1 rotor diameter from the ground. At that distance it's close enough to compress the air between the ground and main rotor. Unfortuntunely if you pitch the heli with the cyclic it'll shoot off in the direction it's pitched. Like the heli was on a compressed spring. The real benefit of OGE (Out of Ground Effect) hovering is pitch changes do not release that column of compressed air and as Heli Bat said this makes OGE hovering easier.

Heli-Bat you were explaining tip vortices. This happens at the rotor tips because the air above the rotor is at a lower pressure than below it. This also means no lift comes from this part of the blade. Tip vortices are at there worst in a hover, but they don't effect stability as much as lift . In fact tip vortices seem to have little effect on RC helis because most have an excellent thrust-to-weight ratio.

Hey Carfanatic as far as mechanical trim settings go the best advice I can give is make sure the swash is flat and level in the neutral setting (right stick centered) because my heli's wasn't. Factory test flight don't think so. I also had to increase tail rotor trim so it would stop spinning about it's vertical axis.

Hope she flys smoother for ya

carfanatic

thanks for the info guys. I think alot of it might be ground effect. I really need a bigger place to practice. I'll look at the swash plate tonight, I think its pretty level though. Hoping my g3.5 sim comes today, my axe is down with a broken tail rotor, waiting on the parts. once I fix it I'm gonna take it to work and fly it in the warehouse, that will give me alot more room to get in the air and let it wonder around a bit.

PilotLight

My Feedback: (1)

Sounds like we have a real heli pilot, thanks for all the advice and terminology.

One thing I found when adjusting the trim on the transmitter is if the heli is trimmed for hovering out of ground effect, then lowered into ground effect, it is out of trim. The lower power required for hover, causes the tail to drift a little IGE.

I usually trim for flight OGE for hover practice about eye level, but lately I've been working on Nose-in practice so I trim for IGE and hover about 3 inches off the floor. The added stablility of bumping the training gear on the floor once in a while helps keeping me from flying off when I get slow on the sticks.

Heliko

Hey PilotLight sounds like you got the trimming down pat.[sm=thumbs_up.gif]