I have a Global Freestyle which is sort of a blend of a pattern and 3D model. Although I am not a pattern flyer (yet) and this is not really a pattern plane I want to find out the best way to check and correct the trim on the Freestyle. It is a new plane and have flown it for about 1 1/2 hours. I am also a full scale instrument instructor and both pattern and 3D RC flying is appealing to me because of its precision. I would like to learn how to troubleshoot the Freestyle for its trim (engine thrust, control trims, etc). I could just fly it and manually make corrections, but I would rather have an RC plane properly set up. There is usually some wind when I have flown the Freestyle and I noticed that in sequential loops it sort of cork screws, but I am not sure if its the wind (the Freestyle has a large rudder) and/or it is not trimmed properly. I could not think of anyone better to talk to about this than a pattern flyer. I like to build and hope to build a pure pattern plane in the future.

Winglift,

It could be an elevator half is out of adjustment or it could be a wing low entry. Both can create this problem. Go to this link http://www.nsrca.org/trimA.htm and print a copy of the chart. You do not have to do all of them but the first 5 or so are important. Instead of doing a loop, do vertical pulls in front of you and directly in line with you to the side, so you can clearly see what the model is doing. Also the vertical dive and pull out will tell you a similar tale.

Marty

Are you are saying that I do a vertical pull as the plane passes in front of me from left to right or visa versa, or do you mean to have it coming towards or away from me when I do a vertical pull?

I have printed the trimming chart and plan to do some test flying this weekend. Thanks for the info. I will let you know what happens.

Okay, I printed out the trimming chart and flew the Freestyle. I attached two straight sticks to each have of the elevator and there is no difference in deflection. There were two tests that I concentrated on, the first was the CG and I used method 2 since the results of method 1 seemed inconclusive. It required a great deal of down elevator to hold level flight, but I know that the CG is set precisley to specs and that doesn't make sense to me. I also did the side thrust test which is similar to what you suggested that I do and found that the model veers to the left which indicated that I needed to increase the right thrust.

Now, here is the question. Although it is set up according to specs, why would the CG and Thrust be so far off? I did put the largest size engine, and perhaps more, in the airplane which is a YS .63S, but still balanced it to the prescribed CG. Not sure about the right thrust?

forget what the plan/kit says the cg etc should be, it's how it flys that counts and if you need to hold in a fist full of down elevator when inverted, the cg needs to go back! Side thrust depends on prop/engine choice so there is no one set value. If it pulls to the left (ie you need to add a bit of right rudder trim to get it to fly vertically hands off) then more side thrust is needed!

If would say to absolutely correct your right thrust, IMHO this is one of the most important aspect in order to fly precisely. Regarding CG,I think the inverted flight test is not accurate: you say you have to keep a large amount of down elevator, but here EXPO settings may render the test misleading. If you have a great amount of expo, a great stick travel could lead to a little elevator throw. For CG, I prefer the following well-known test: 45 deg. climb with throttle applied (the amount used to trim for level flight) then do an half roll and let the plane go: it should follow 45 deg climbing line, with tendency to falls down.

Hope this helps! Keep us informed about your results...

How did you know that? Yes, I do have a lot of exponential on the elevator. I did that for the first few flights. I will try the 45 degree test and let you know what happens. If the CG is correct I am assuming that it should hold that line for a short time before dropping or nosing over or would it just lose altitude in the 45 degree roll attitude since my current engine/prop will not give me unlimited vertical climb?

So, if you have a lot of expo on elevator, perhaps the model is not too nose heavy. Do the 45 deg test and see what happens. A correctly trimmed aircraft will tend to recover pitching toward earth after keeping the line for a while. A tail heavy airplane will either pitch toward the sky or will keep the line.

As you see, there is not an objective way to trim the aircraft: in the end, it is a personal feel that must be reached. As great pilot Don Szcscur suggest, for precision flying is preferrable a little nose heavy setup, otherwise your airplane will not track well (and axial rolls are more difficult to perform); other way to check your CG is the stall behaviour: a nose heavy will tend not to do a visible break in pitch, while an aft CG will make the airplane more sensitive in pitch.

I think it's all, let us know the result of the tests!

http://www.australianpatternassociat...20Trimming.pdf