Adding digital trim to your transmitter after using the leveling tool
has a negative impact on your helicopter setup. Let me explain my
reasoning for this.
Once you have used the tool, the swashplate should be completely level
across the entire collective range. This being true, adding trim
to the swash plate can only be masking another underlying
problem. The most common of these problems is a poor for/aft
center of gravity. I fly the stock SE kit on 3 cells and have
found that normal radio locations make it very tailheavy. The
correction for this however is not to simply give forward trim to
counteract the offset CG. Instead spend a little extra time, and
move your radio gear around to get the CG where it should be. In
my own experience I have found that the helicopter flys much better
with the CG directly under the mainshaft even if I'm only staying
upright.
Consider the case where an average pilot has a tail heavy helicopter
and adds forward trim. Now think about what will happen when he
does a flip or anything inverted. That sub trim will be making
the tail heavy helicopter twice as bad, because what fixes the problem
upright worsens it inverted.
The same thing happens when you consider the tail rotor. Because
the tail is pushing air to one side, theoretically the helicopter will
need left right trim to keep it in once place. If this trim is
added again things become twice as bad during inverted maneuvers.
Also remember, wind plays tricks on pilots when it comes to determining
if a helicopter is in trim. Always check the trim, and they do a
180 degree pirouette and see if you have the same result. If you
are able, also check the trim inverted. If you find for example
that the helicopter always tilts toward you whether you are tail in or
nose in, then you can assume that the wind is causing the tilt in
your helicopter, and not incorrect setup.
Another thing to mention, adding sub trim to the radio adds some offset
to all the servos you just spent time centering. If you know
everything is centered, level, and at 0 degrees then you have a perfect
setup. As soon as digital trim is added one servo has rotated one
way while another servo the opposite way, causing responses between
servos to be different along their entire travel.
Please feel free to discuss this or anything else on this webpage in
the discussion forum. I check it often even though it doesn't get
much activity. I hope this explains why adding digital trim is
not a good idea.
Mike Trueblood
Mike@TruebloodEngineering.com
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