Herb-RCU

My wife's trainer is a Tower Trainer .40. It has a GMS .47 on it. One of my frustrations with it is that it won't do a straight loop. It kind of turns through the loop. I have tried balancing it laterally but it still does not loop straight. I can't understand why one side of the plane came out significantly heavier than the other side.

Another thing that I considered was p-factor. I'm not sure if this plays into this or not, but it may. Possibly a smaller prop would help. It has an 11x7 on it now.

Any ideas?

Thanks,
Herb

rcav8or

My Feedback: (5)

You don't give your flying skills and experience, so it's hard to say without sounding like a wiseacre, but usually, a loop that does not go up and over perfectly round, is caused by the rudder being out of trim. It can appear that everything is in trim, but you could have, say, right rudder in, causing you to have left aileron trim in, and it appear to fly level and straight. But when you go to loop, the rudder comes into play more, and it causes the plane to track in a sideways (of a sort) loop.
Prop ok, probably not the cause at all...

Here's a great page, that gives the steps in order, of properly trimming a plane, along with some other good stuff (scroll down the page a bit)...it doesn't go into rudder very well...

trim chart and other goodies

Try doing your loop, and as it goes up, if it's always turning to the right, give it a little left rudder, and vice versa...if the turn goes away, trim a little bit that direction on the rudder, then correct the ailerons...

The other possibility is the lateral, but you sound like you have that under control...

I know I had the HARDEST time, learning to trim out the rudder correctly, and it took looping directly away from myself, to be able to do it...

Let us know what you find, when you find it...I am sure there will be others here, who will offer other ideas, and you are bound to find something that will work!!

rcav8or

My Feedback: (5)

one more thing, make sure you are not trying to loop too tight, sometimes, it can cause a "snap" effect, that will try to roll out at the top.

Also, check your wing for any warp, as that can do a lot to your trim - they will fly, but everything will be "out of trim", in a combination to appear in trim (sorry, clear as mud, eh??)

If you don't know how to accurately check for wing warp, post here, or email me, and I have a dirt-cheap way of telling...

R

Divesplat

My Feedback: (7)

2 other thoughts on this;

Without right thrust on the engine, P factor here, the plane will pull to the left and most trim this out with Rudder, hense the above post. Most trainers aren't concerned with right thrust as it usually only affect vertical manuevers, stall turns etc.

The second common problem is the elvators not being equal at nuetral. so the plane twists a little as up or down is given. In a trainer it is seen mostly with up. Carefully measure the elevators distance from a solid point(ground table etc.) Make sure the horizontal stab is level to the surface first.

Hope this helps.

ed

Herb-RCU

Thanks for the input. As far as my flying experience, I have flown since I was quite young. I can fly sport planes fairly well but I haven't flown much else. Of course, this is all my own opinion. I think I'm a little weak in the setup of the airplane and I know I can learn a lot. Hence, why I asked this question. I am also a private pilot which may not apply at all here, but....

rcav8or, I am interested in knowing how to check for a warped wing. I worked hard to build this thing straight but I'm not sure that it came out that way. You also mention a "snap" effect and I have seen this on the forum before relating to warbirds. I'm assuming that this is another term for "accelerated stall".

Lastly, the elevator thought was a good one, but it is a solid piece all the way across.

Thanks for replying. I'm not real concerned about this plane being able to do aerobatics, I just want it set up well. I also want it to be as easy as possible for my wife to fly. I also want to learn more about setting things up.

Herb

rcav8or

My Feedback: (5)

It's pretty easy, once you know about it - you need several straight dowels, about 12 inches longer than the chord. I use either fiberglass pushrods, or arrowshafts, which I always have laying around, because I use so many of them. You also need several rubber bands, the kind you hold the wing down with (#60, if I remember right).

The idea is to take one dowel, and place it underneath the wing, perpendicular to the wing (parallel with the ribs), so that an even amount protrudes front and rear, probably about 6 inches, and just a couple inches in from the wingtip. Take a rubber band, and stretch it over the wing, to hold the dowel in place. Sort of like the top view illustration below (I hope it turns out).


_!_____
(_______
!

Then do the same on the other end of the wing, with the other dowel. This should (if the wing is straight), put both dowels in the same plane, aligned with the bottom of the wing.

Now for the fun - sight down the wing from either end. Both sticks should be exactly parallel with each other, i.e., when you look at them, they should line up. If there is warp in the wing, or the wings have different incidence, you will see one stick at a slight angle to the other, showing that the bottoms of the wings arent' the same...hope this makes sense to you...sorta like if you hold your right arm out in front of you, bend your elbow 90 degrees, so you are looking at your forearm and wrist, then do the same with your left arm. Keep your elbows at the same height, but lift your right hand, you will see the angle and that's what you will see with the dowels...

Now, put the wing on the plane, set up the centerline so it is level, and look again from the end of the wing at the dowels...one should line up with the center line (unless it calls for positive incidence), and one won't, if it's warped. Use the one that DOES line up with the center line, or positive, as your reference. That one should be correct.


If you find you have either twist or warp, you can usually correct it, by holding down the correct half of your wing flat on the table, (the reference), and with your heat gun in hand, OVER twist the other half past the correct angle a bit, and reheat the covering and let it cool. Four hands help a LOT here!! When you let go, it will relax a little, that's why you over twist, but it should hold, with a lot less twist in it - you might have to reheat it several times to get it just right, just don't overheat and melt the covering. When you twist it, you will see wrinkles in the form of diagonal lines, across the wing, between the bays...when you heat it, those will dissappear, and you will know that you have reversed the twist somewhat.

If this doesn't make sense, let me know, and I will take a picture and send it...

Herb-RCU

Thanks, rcav8or. You explained it well. It makes sense to me. I will try this out sometime in the near future. I'll try and post the results here. However, the weather the way it is up here in WA, flying is limited.

Thanks for your help,

Herb

GalenB

My Feedback: (18)

Herb,

Where in the state of WA do you fly? If you are near me maybe I can help...

Cheers!

Galen

Herb-RCU

GalenB,

I'm over in Walla Walla. I think that is the opposite side of the state, right?

Thanks,
Herb

GalenB

My Feedback: (18)

Hi Herb,

You are much too far away! I live 17 miles east of Seattle. What's the flying like in Walla Walla? Weather? Wind? etc... Someday I need a place to retire to that is not in King county...

Cheers!

Galen

Herb-RCU

GalenB: The weather here isn't great, but probably better than Seattle. We don't get very much rain, but it is frequently windy. I have headed out to the field multiple times when the wind was calm, but by the time I got there and got setup to fly, the wind had already picked up. We have one of the largest windmill fields in the NW or something like that about 15-20 miles from here. That should give you some idea. Also, it can get pretty cold here but I'm not sure if it is much colder than where you are. The flying field is pretty nice, though. Paved runway and cemented sidewalk. There is also a nice grass area next to the runway. However, the runway isn't that big. Check out the club website:
www.proptwisters.org
They allow you to fly there if you have AMA. You don't need to join the club. If you are in the area, you should check it out. However, unless you have family in this area, I doubt you have any reason to come this way.

I'm looking forward to moving to So. CA at the end of the summer so that I can fly more often. That is about the only reason I'm looking forward to the move though. I prefer not to have to chew my air. Eventually I'm planning on moving to N. CA where the weather is much more moderate and the number of people is much less.

Personally, Walla Walla wouldn't be my first choice of places to retire. I would head south if flying is your goal.

E-mail some people at the club and see what they think. I have lived only in a limited number of places and so my places to compare to are limited.

I hope that this helps,
Herb

Herb-RCU

GalenB: I was thinking last night (Usually gets me in trouble) and I thought that I may have overexaggerated the wind condition here. It is windy, but there are much worse places. See what the other club members think.

Herb