CG and thrustline for F3P?

[pkruse]

For F3P, do you offest the thrustline? What do you check for in flight to see that the thrustline is set correctly? What do you check in flight to see if the CG is correct?

Thanks,
Paul

[David Kyjovsky]

For F3P, do you offest the thrustline? What do you check for in flight to see that the thrustline is set correctly? What do you check in flight to see if the CG is correct?

Thanks,
Paul

I have this method: (to set the thrustline) at first I make a vertical power off dive (as far as it can be done indoors) to set up a neutral elevator trim. Do it several times until you feel that you nailed it. With this trim and with rudder optically neutral I offset the thrustline to achieve a straight climb vertically up without any pull, up/down nor sidewise. Usually I end up with a huge amount of right thrust - so much so that I originally thought that it could not be right. Don't worry about that too much, as long as the plane climbs straight up... or prop-hangs clean...

The CG is much more a matter of personal taste ... I have it fairly aft, for level flight I pull only the slightest bit, for inverted I push about the same (small) amount. The advantage is, once you start a horizontal line, the plane keeps the line more or less on its own.. i.e. you dont have to constantly juggle the stick to keep the plane level. In F3A you have a lot of time and space to make corrections, often before the judges see the reason for it and the fact that you made it. Not so in F3P, where every correction is too obvious. Remember, in F3P the judges see everything, as it happens right in front of their eyes.

In the F3P sequence, I have this test for correctly set up CG: in the first manoeuvre, the inverted cuban 8, you pull to 45° line, release elevator, make the half roll, watch the line after the half roll. I like to have the CG such that the line before and after the half roll is the same, hands off.

I am sure that other people may have different preference for CG location, with similar or better results... but this is how I like to do it.

Maybe it helps,

David

[pkruse]

Thanks David!