I'm currently learning to fly on a buddy box. I have used several different instructors...
I'm flying a flat bottomed wing Hangar 9 Alpha 40.

My question is this:
When you trim a plane for level flight, do you use full throttle, or approx. a 1/2 throttle setting? Why?
Or, do you trim it based on what you are currently flying at. Most of my flying has been right about 1/2 throttle...if I speed up, it wants to rise quickly...then I'm trying to keep it down with down elev., all the while trying to maintain level altitude in my turns...I suspect if I slow down it would stall, or descend... is there one correct setting? [sm=confused.gif]

TIA,
Bob

as in full scale you should re trim for the power setting you are currently using provided you will be using that setting for awhile.

Due to the airfoil of the trainer wing, it will tend to rise as you increase in speed. The good part of that is that it means the wing has a lot of lift which is good for a trainer.

If it were me, I'd find a throttle setting where I am comfortable flying and trim the plane to fly level there.

If you slow down or speed up for short periods, compensate with the elevator to keep it level. If you decide to speed up or slow down for much longer periods of time then maybe trim it for level flight at the new setting.

I would trim for about half throttle or maybe a little more. That way, when you give more power you ascend and with less power you descend. It is also easier than messing with the trim tabs everytime you want to change speeds.

If the extra lift is severe, you can add some down-thrust to the engine to help correct for it

And, this is called trimming for level flight no matter when you do it. But, manually holding the elevator at that setting isn't the solution.

So, yes, you do trim for level flight after a throttle change. Get used to it. That is part of flying. Sooner or later, you will find that after you take off, you may find that your trim is the throttle. Meaning you will adjust your throttle for level flight. Often, though a click or two of elevator will do the "fine tuning" on that trim. But, when you change the throttle for a maneuver, well, once finished, you either return to that setting or trim the elevator.

CGr.

Thank you all for your quick responses! This is great, and much appreciated.

As I progress, I'll have to make sure that I get some training on trimming an airplane at various speeds... as CGRetired stated, I need to "get used to it" .... I imagine there will be many things that I'll have to get used to (like takeoffs and landings!)....but, I'm having fun...and just beginning!

Thanks again,

Bob

Trim to what you like and are most comfortable with, I trim for full throttle for most of my planes as I prefer it that way. But most important, no matter what you trim for, you will need to make adjustments. It means that you must be in control of the plane at all times.

Like what Minn says, if its really bad on full throttle then put in some down thrust or mix with some down elevator if you wanna take the easy but not the best way out. I do that for my big Lazy Bee as she climbs a lot. Fly more and you will gain more experience. Most of all have a ball of fun!

I trim for level flight at 1/2 throttle and leave it there....now think about this......true you will climb with power on.....but what are doing when you add power? taking off, or doing a manuver where you want altitude....can't think of many times I've added power and down elevator...nope...I don't add power on an outside loop until I'm near the bottom.....
When i have a student up I have him start at 1/2 throttle...exactly where the airplane is trimmed for.
When the power is off or reduced the airplane sinks this is exactly what I want as I'm landing or doing a manuver where I want to reduce altitude...I can use throttle to reduce the sink rate or go to a positve rate of climb on a go around with throttle....
If an airplane is trimmed for level flight at power then as you reduce power you either have to retrim or give up elevator...having alot of up elevator input on approach is not a good thing....
Bottom line is this is how I do it and my reasons.....as a student do as your instructor wants..learn his way and then after you solo you have a broader knowledge base to make your choice...
Good luck

I have too agree with jetmech on this one. Half throttle is where you fly most of the time and in flight you want too stay level except you are doing a manuever, landing or on take off.

But I do have a question though - not all engines are the same - wouldn't you be flying some engine-plane combos at different throttle? For example - if you fly normally in a circuit for instance - you would have your throttle just under half since that then reaches the speed of the smaller engine planes. I don't know it's just something which occured to me now. Would you then trim it for that throttle setting?

Basically you trim your plane for level flight on the throttle setting you will fly the most?

I have a computer radio..so I don't have to retrim for different models......I guess if I didn't have a computer radio I'd try and mark the transmitter some how so I'd know where to set trims

Retrim as you fly, based on your needs.
In fact, once trimmed correctly, your re-trim will be a click or two not more, and that becomes subconscious and automatic with time.
It is mostly a matter of getting used to things basically, I am sure you won't worry about that in a couple of months.

I prefer to trim it level at 3/4 throttle for easier low passes.

Hi!
Some advise from a competition pilot !
You always trim a model airplane for level flight at full throttle!
The plane will then fly straight as an arrow! A correctly trimmed airplane will fly fairly straight at reduced speed with nearly no elevator correction needed. If the plane drops it's nose at half throttle the plane is nose heavy and should be trimmed right! This applies to all model R/C planes, scale, pylon and aerobatic.

I agree with what your saying but will disagree with most trainers available today. I have balanced, trimmed at full throttle, 1/2 throttle whatever and most high wing trainer type planes when trimmed at full will drop fast at 1/2 throttle or below. Now with the right setup of wing, engine and everything else one can acheive this in most cases, but a normal ARF version trainer from most MFG. NOPE trim to 1/2 throttle gives you lift when taking off and decent when landing. MHO.

Hi!
What then happens at take off is the plane will climb more than needed...No good when you are a newbie!
Better to just trim for level flight at full power! That's the way most of us R/C fliers do it!

Thanks for the additional replies!
My instructors have been setting the trim at about 1/2 throttle. This is the setting I have been doing most of my flying. But, I have seen w/o enough power, and a stiff headwind, my trainer will balloon up and stall....(Not good, makes for some anxious moments! )
Seems to be some good points to doing full, 1/2 or trim as needed perspectives. I'm sure I'll form my opinion based on these inputs, as well as my future experiences.
Bob

Well, I'm an RC flyer and I trim at half throttle. And I was taught by three master level pattern types and one international level area champion. Must be something there.

AB Bob:

In order to understand the trimming in pitch (horizontal level flight with no nosing up or nosing down), it is good to simplify things.

In order to analyze what happens to the model, let’s disregard some physical facts:

Imagine that it is only the wing what makes your model fly by generating a lifting force.

That force varies in lineal proportion with the angle of attack (AOA) between the wing and the direction of the air hitting the wing.

That force varies in square proportion with the velocity of the wing thru the air.

Now, imagine that the only function of the horizontal tail (stabilizer + elevator) is to force the wing to keep a certain AOA.

The horizontal level flight only happens when the lifting force and the weight of the model have the same value (and opposite directions); it is a perfect balance.
More lift, the model climbs; less lift, the model descends.

That balance of forces that allows a sustained level flight is achieved for a unique combination of AOA and wing velocity thru the air, for a particular model.
In a practical range, less velocity requires a bigger AOA and vice versa.

The velocity of the level flight respect to the wind is controlled by the throttle.
The angle of attack of the wing for the level flight is controlled by the deflection of the elevator respect to the stabilizer, which can be preset with the radio trim tab (normal way to do it) or by constant manual input.

So, as stated here by others, the pilot chooses the velocity for level flight, and then, trims the elevator to achieve the correspondent AOA of the wing.

Now, changes in throttle are powerful, because the air velocity increases lift in a square proportion.
For trainers, which are meant to return to level flight by themselves, the geometry between the wing and the horizontal tail (decalage) makes them more sensitive to any changes in air velocity; some simply cannot fly level for high velocities, even with big adjustment of trim.
When flying upwind, the model moves slower respect to the ground, but the wing encounters the same air velocity and the balance remains; it is only when throttle is added to make it move faster respect to the ground that the model balloons up, due to increased lift.

You may be able to modify the decalage by adjusting the wind incidence, if the problem is too acute; check the following old thread:
http://www.rcuniverse.com/forum/m_75..._1/key_/tm.htm

Simple. Right.

Lnewqban,
Whew!
AOA, decalage, etc.... I have ALOT to learn about!
Thanks for the link.
Bob T.

AB, yes, there is a lot to learn. The best thing you can do is sift through the BS and get to the heart of the issue.

There has been, and always will be, a lot of theory and "full scale experience" throw in these forums and posts, especially when it comes to maneuvers and some basic flight information.

The toughest part of being a novice is to recognise what is fact and what is fiction, or theory. Most of us will give you what we believe is the best information based on our RC... note RADIO CONTROL experiences, which vary quite a bit from some of the full scale stuff that we read about all the time here in the forums.

Go ahead and fly and remember that your experience will come with time and, as my instructor always said, by burning fuel. Get out there, experience the fun, the joy of RC flight and do your thing. Practice, practice, practice. That's the only way you gain experience.

What you will find is what seems very difficult now will, at some time seem routine at some time in the future. Your responses will be automatic because you learned it and you learned to fly. You will recognize when the AC needs to be trimmed and when it does not. You will learn how to do an appropriate downwind, base, final, land. You will learn that once you are "wheels up", you let the aircraft gain airspeed (you can't really see it, but you can hear it and feel it) then you can begin to make a turn and climb out to your "working altitude" and then begin to play.

What I suggest you do is continue to fly but do something new each day. Not each flight, but each day. Just a small change, but do something to improve your skills. Repeat it over and over again. And, at the same time practice some basic stuff.. emergency procedures (dead stick is the best one to practice) and do touch-and-go's to get the landing sequences down and in memory so that it becomes automatic.

Again, sift through the BS and get to the basics and expand from there. You will be amazed at how much you learn in one season, and how much you progress in one season.

Above all, don't sweat the small stuff. Just practice basics as often as you can and fly and have fun.

What I do is this: I arrive at the field, I grab my frequency pin, unload the car, and set up on the bench. I completely inspect the plane to make sure that it is ready for flight, including a check of the battery voltage using an ESV or the installed Voltwatch, then I assemble it (connect servo wires, wing on, bolted or elastic banded down, and make sure all is square). Then I range check it before starting it up do that I am sure all works. Then I fuel it up, briefly check everything again, then start the engine. Once started, I tune it and make sure it is ready for flight, then I do another range check. Again, if you have a voltwatch, check it to make sure all is well with the electrical system. Now you are ready for flight.

Next, once started, I walk it out to the flight line (carry it) and set it down on the centerline (announce your presence on the flight line to other pilots). Now, I hold the plane and run the engine up to full throttle to clear it out and get it ready for flight. You can almost hear it yelling at you that it's time to fly!!!

Take off and fly it. For the first flight of the day, I do several orbits and get myself back into the groove. As you get older, you will find that you will need a few orbits, maybe a couple of tanks of fuel, to get back at it and get yourself ready to fly for fun. It does me.

Next, well, I do some emergency procedures. I pick a spot in the sky and idle the throttle, and initiate a "dead stick landing drill". I don't land it, but come to a point where it is ready to land, then add throttle and go around. I may do that once or twice, but I do it on the first flight of the day, every day. It is not only really good practice, but, it can be fun and a challenge.

The next thing I do is make several approaches, not necessarily landing, but approaches and go around. Then, I do a few touch and go's. Once all that stuff is done, I get into my fun flying and make the best of the rest of the day.

I can tell you this, all of the practice, the drills, the emergency stuff, can be fun, is always fun and a bit of a challenge depending on where you put yourself in the emergency situation, but it adds to your experience. I can tell you this too.. I've had a few emergency experiences and all of them.. ALL OF THEM.. have resulted in good and safe landings. Some of them long, meaning down the runway a bit, but the plane survived and I was a happy camper.

Best of luck.

CGr.

All this takes only about 10 to 15 minutes but it is time well spent.

AB Bob:

Consider this last post from CGR as an excellent advice for speeding up your development as a RC pilot.

Do not get too much into the physical process at the beginning; it is something that practice will teach you over time more than books.
I just tried to simplify the trimming of pitch for you, which was very confusing for me when I started flying.

Just a few more suggestions:
1) Try to remain learning from only one instructor. Most instructors know enough to teach you well. Patience is the virtue of my dear instructor that I appreciated the most.
2) Try to learn to be ahead of the model, so you really control the flight. This is very hard to achieve during the first times, when the student just reacts to what the model and the wind decide to do.
3) Learn slowly, and always. You will not be learning whenever you feel too comfortable. The better pilot you become, the more joy you find in this challenging hobby.
4) After feeling confident enough, practice setting the trims slightly off and re-adjusting them in flight.
5) Do not allow the fear to crash to paralize you and to diminish the fun.
6) Safety first! Comply with the rules of your club. Be corteous and safe. Never ignore that spinning propeller!!