rolling left
 

Last weekend I maidened my VQ Warbirds P-51D. Has a Saito 82. My third plane and first sport/scale warbird. Read a lot of posts about not too much throttle too fast, be prepared for some right rudder, etc. So, everything went good on the take off, was moving pretty fast down the runway and started lifting off. As soon as the wheels were off the ground the plane banked hard left and started to nose in. I was able to correct, and get some altitude, but was rolling left real bad. So much so that I had to have my friend come over and input some right aileron trim. I then got the wheels up and that helped bring the plane to level. Finally got her pretty well trimmed out, flew around for a few minutes, and landed. Flying straight and level my ailerons are about 1/16 to 1/8" up on the left wing and down on the right wing. The plane flew great after that, but something is out of wack. Does anybody have any ideas for me to check? Is it possible that the plane has something twisted (not the pilot[X(]) that I can check?
Thanks,
Pete

RE: rolling left
 

check your left to right balance, maybe one side is heavier than the other

RE: rolling left
 

I agree with gamesbeer1, check lateral balance. Support the nose and tail lightly. She'll fall to one side or the other if out of balance. Hope this helps.

RE: rolling left
 

G'day Mate,
As stated above, check lateral balance, & check the wing by holding it by the trailing edge, & looking straight across the wing at eye level, look for twist in one side or the other.

RE: rolling left
 

That much aileron trim suggests more than a lateral imbalance. And if it were a weight imbalance problem, it would show up as needing less aileron trim with higher speed. The weight doesn't change but the aileron trim gives lots more effect with more speed. With warps that can be trimmed out, the warp and the trim are basically working with the same airspeed and somewhat cancel out.

Can you take a digital picture from directly behind the airplane?

Keep in mind that the airplane could have been trying to roll with both wheels on the ground and one was against the runway, stopping the roll from happening.

RE: rolling left
 

This sounds like tail-feathers that is not aligned with the wing. Take a look at the rear of the plane from about 10-15 feet back and eyeball the horizontal stab alignment with the wing. They should be the same.

RE: rolling left
 

I'm guessing this is a .40 size plane, and also with the Saito .82 you're swinging a 14 or 15 inch propeller. I would guess that it's mostly P factor. After you got it all trimmed out, did it try to roll right if you suddenly let off the throttle? A lot of the 3D guys will overpower a plane so they can swing a massive prop that will allow them to hover at just more than idle. The difference is that 3D planes have much more wing area, and the P factor isn't as pronounced as it would be on a sport plane. Try a smaller prop ... maybe a 13X8 or 13X6 and see if that helps. If not, it's probably either tail feathers or latteral ballance.

RE: rolling left
 

Things to check: Lateral balance, uneven ailerons, wing twist, uneven elevators, horizontal stabilizer parallel to wing.

RE: rolling left
 

Hi!
That much aileron trim means wing has got wash-in! That means one wing is flying with its tip at a more positive angle than the rest of that wing half...and this must be fixed.
If its an ARF plane all you do is blast on with a heat gun,hold the wing between your legs... and twist the wing in the right direction...and hold it so untill it calms.

RE: rolling left
 

If it banked hard left you would need UP on the right wing ( right wing down, trailing edge of aileron UP ) and DOWN on the left wing ( left wing up, tailing edige of aileron DOWN ) to compensate.

This is the opposite of where you have set things...

So, as others have stated, you have a BIG lateral inbalance or a wing/control surface is warped, because you are actually ADDING additional LEFT roll to the plane with the trim as you have it.

Or am I reading this wrong?

RE: rolling left
 

Lateral balance my foot! Not unless he's got 3 ounces hanging on one wingtip.
I'll bet the wings themselves are warped.


Remember, the first word in ARF is ALMOST!

RE: rolling left
 

Yeah with this "strange" compensation, it has to be a warp.

RE: rolling left
 

LOL! I love it.

And, as a wise doctor once said: "a child with chicken pox can also have the measles."

Sometimes it is a combination of faults. ;-) It could have lateral imbalance AND wing twist.

RE: rolling left
 

It could also have left thrust and up thrust.

Sometimes focusing just takes all the possible solutions out of the field of view.

RE: rolling left
 

Thanks for all of the responses. It is a .40 size ARF plane. Has a 13 x 8 MAS prop, but I am plannig on changing it out to 14 x 6 to see how it flys. I made a mistake and you guys caught it. It was banking to the left. But after trimming it, the aileron is up 1/8" on the right wing and down 1/16" on the left wing. I will fix that difference. I did the lateral balance and it was fine. The tail and rear wing appear to be in proper alignment with the wing. But, looking down the wing from one end to the other it has a little twist in the wing from tip to tip. Can't really take a picture that would show this. Hope you guys understand what I am trying to descibe. Not trying to get away with anything, but the plane flew pretty good after it was trimmed out. Will it cause a problem if I just leave the wing as is? I am a little afraid of trying what "jaka" said to do about removing the twist. I did a few aileron rolls both directions and it seemed pretty normal to me. But, I don't want to crash the plane if there is a possibility that the twist will get worse. Got to tell you, this being my third plane, it scared the heck out of me when it rolled over on take off. I was shaking so bad after it landed I did not even fly until the next day!
Thanks again for all of your help.
Pete

RE: rolling left
 

Twist is easy to detect on a flat bottomed wing (rubber-band dowels near each wing tip and stand bach a few yards and look to see if the dowels are even). Sometimes it takes longer to find two straight dowels (I have arrows that makes it a bit easier). It's a tad harder on a symmetrical airfoil, but you can do it with equal sized blocks between the wing and the dowel near the trailing edge

An incedence meter makes it fairly easy. If you can't measure it you shouldn't try to correct it. If correcting the uneven ailerons helps, and you'll have to fly it to test that I'm afraid, then you should probably either seek help in person or invest in an incedence meter.

Some folks are good enough to spot it visually by setting the plane on a level surface and sighting along the wing from the rear, using the horizontal stab as a point of reference.

PS - when you do fly it again resist the urge to yank it into the air to gain altitude. Get up plenty enough ground speed and then fly it up at 15º of climb. If you yank it and stall it even an untwisty wing with even ailerons won't save you.

RE: rolling left
 

I'd fix the warp. The effect of using the xmitter trim on the ailerons will vary with the plane's speed and limit aileron travel in one direction compared to the other side -- IOW, its just a hack.

When you start learning how to really trim an airplane properly, you'll be way ahead of a lot of supposedly "more experienced" people.

RE: rolling left
 

Actually, there is a way to see twist and it's easy to do.
It's not easy to describe, so I'll upload a picture to help explain. And when I'm done explaining you'll not only see a warped wing, but one that's got wash-in.

Setup the airplane so you can look at it from exactly the center rear. Move the plane or your eyes so that you can see both wings equally, and so that you see a couple of things about those wings. You can tilt the tail up and down until you see the Trailing Edge of the wing and it looks like it is exactly in the middle of the top of the wing and the bottom of the wing. If the wing isn't warped or twisted, as you inspect the wing from root to tip, you'll see just as much top as you'll see bottom. Look at the wing from the root out to the tip. Both sides.

I added a couple of black lines to the right wing to help the picture show what we're looking at. If you look closely, there are really 3 lines, two black ones I added, and a white one that's a bright white TE thanks to the camera's flash. And if you look closely, you'll see that close to the fuselage, the top and bottom of the wing look about equally thick. But as you look out toward the tip, notice how the TE seems to twist down? That's a warp. And it's one that is called "washin". And it's not what we usually want, if we want any "wash" at all.

OK? Pretty easy to do, isn't it. It helps when you're at the field to have the sun at your back, btw. And there are a couple of ways to do the lineup. If the wing is cambered, you can line it up the way the stab/elevator is in the picture, only in the picture it's "upside down" for a cambered lineup. Basically, you tilt the tail down until the TE of the wing starts to line up with where the bottom black line is on the picture. And as those two lines come together you can see if they're coming together equally along the span.

The idea is the same for both methods. You compare the TE's "line" to the line along the top of the wing and to the line along the bottom of the wing. Do what you can see the best.

Now, about "ironing out a warp"........................

RE: rolling left
 

Ironing out a warp in a built up wing is easy. I find it easier to do with an iron, but in our hobby there are often 2 or 3 "best" ways to do most things.

You simply block the wing, usually around the middle, so it's steady, and with one hand you twist the wingtip so that the warp is twisted out. With a builtup wing, you'll see wrinkles in the covering. Iron 'em out while you hold the wingtip firm. You need to hold the tip firmly until all the bays are tight, top and bottom.

If the warp comes back a bit after you thought you were done, do it again, and twist a bit farther.

Pretty easy to do. And of course, you check to see how you've done with the technique as described in the post above.

;)

RE: rolling left
 

Ah that's MUCH better.

1/8 to 1/16 means that you set the trim to combat p-factor & engine torque.

You merely need to get the travel on both wings equal... e.g. both should be between 1/8 to 1/16", but the amount should be equal.

If that's all you need, then it is unlikely that you have a warped wing.

After fixing the difference, trim the plane out for level flight and take it up as high as you can.

Then set the engine to idle and head it straight down.

Watch to see if it rolls.

You SHOULD get a slight roll to the right because of your trim.

If it dives without a slight rightward roll then you have some warp. If it rolls right because of your trim the plane is fine.

RE: rolling left
 

Hey, thanks a lot for the responses and the help. da Rock, that is a great picture and explanation. I was just eye-balling the wing before from one end. So, I am going to do some more looking at it like you describe to see just how much, if any, twist there is. If it's VERY little, I am going to do opjose's high altitude test. That sounds like more fun. :D I won't be flying the plane for a couple more weeks, but I will post what happens next.
Thanks again.
Pete

RE: rolling left
 

Well, here is an update. I checked and double checked for any twist in the wing, or tail and rudder orientation, and what I found was almost none. After checking the ailerons I did some "adjustments".

My Mom always told me that sometimes, "if you don't have anything good to say, don't say anything at all". Let's just say that there are a few things about the VQ Warbird plane that I am not going to say.

The plane did teach me some something about patience! Ahhhh, a silver lining:D

After removing and replacing the cowl a few times for reasons I am not going to mention, I was able to fly the plane yesterday.

Keeping in mind that I made "adjustments" to the ailerons, this is only my third plane, and it scared the crap out of me on the maiden flight, I was a little worried about flying.

Powered up, rolled out, and flew beautifully! I was so amazed. Only a couple clicks of aileron trim and it was great. Engine wasn't running great, and after I landed, the engine died. Turns out the vent line came off the muffler. It was my mistake. So fuel it up, adjust the engine a little (without using my tach because I think the vent line was my problem, big mistake!) and take off. Now the engine is running like crap. I installed a 12oz fuel tank, so the plane is a little nose heavy when full. So, I am able to fly around for about 8 minutes to burn off some fuel and start my landing approach and the engine dies (from bad tuning). So here I am dead stick, the wheels are down and I am diving for a little air speed. There is about a 5-10 mph head wind, pulled up a little early, and I figure I am going to stall anytime. But, it doesn't! Wow, it just floats in. I guess that is what a sport/scale warbird is supposed to do? Maybe I got lucky? One advantage to flying off a dry lake bed. One big runway. So I fuel it up again. Adjust the engine with my tach this time. Now it's flying great. I am have a good time flying and decide to slow the engine down for some low fly bys. Now, when I cut the throttle about half, the plane noses up! I don't get it. I think it's the wind causing it to balloon up. But it does it up or down wind. If I cut the throttle down to 1/3 or 1/4 or so, it starts to decend normally. So is this ballooning (for lack of a better description) normal? It wasn't too bad, just kind of funny to cut the throttle and then have to give the plane a little down elevator to make it fly normal. And yes, I powered it back up to full and it flew straight and level. Cut back to half and it noses up. Did this a few times both up and down wind. Weird to me, but I have only been flying for 6 months, so I have a lot to learn. I fly around for about 10 minutes and come in for a landing. I had been landing with a little speed because I was in fear of the stalling in warbirds that I have been reading about. This time I cut the throttle to a click or two above idle, way up in the air on my down wind leg, make my turn to final approach, and the thing just floats in. Amazing to me. Almost like my Pulse XT, but not quite:D Anybody have any ideas that I can check on the balloning thing?
Thanks,
Pete

RE: rolling left
 

It sounds like you may have too much down thrust on the engine if it is ballooning up when you cut throttle.

You will need to add UP thrust, to even things out.

In effect at higher throttles the engine is pulling the nose down. You have things adjusted to make the plane fly level.

When you release the throttle the engine stops pulling down, and the plane balloons up.

Add 2 degrees of up thrust and fly it.

It should tend to climb and you will need to add down elevator to counteract this a bit.

Then fly level at full speed and pull the throttle to idle. If it still balloons up, you may need still more up thrust.

Also make sure that the ailerons ( and flaps if it has them ) are level with the wing chord when the controls are released.

RE: rolling left
 

"Add 2 degrees of up thrust and fly it.

It should tend to climb and you will need to add down elevator to counteract this a bit."

The idea about too much down thrust makes sense to me. I can put some washers on the bottom two engine mount screws between the fire wall and the mount. I am also going to check the ailerons AGAIN, no flaps, just full length ailerons.

Just so I undrestand. Do you mean that I should have to re-trim with some down elevator? Because, it climbs now, but only at around 1/2 throttle.

RE: rolling left
 

The current amount of down thrust is preventing the plane from climbing as it normally would, until you back off the throttle.

At that point the engine thrust is no longer pulling the plane's nose down, so it climbs as you back off.

Typically you see this when you have the plane trimmed for almost level flight at full throttle, then you cut to idle.

If the plane pitches UP you have TOO MUCH down thrust.

What should happen instead is that the amount of down thrust should be such that when you back off the throttle the plane stays level instead.

In your case since the engine pulls the plane's nose DOWN at high throttle, you are compensating with elevator/pitch adjustments.

So when you add the washers to the bottom of the mount adding more upthrust, the plane will initially want to nose up when you fly it the first time.

You'll then need to trim it out again for level flight ( with warbirds a slight climb at speed is normal ).

Now that you add the additional upthrust you'll have or need LESS UP trim on the elevator/pitch at high throttle, so NOW when you back off the throttle the plane should better hold level.

Get it?

At the moment; the engine pulls nose down at high throttle, you ( effectively ) add up elevator trim to keep it level, when you chop throttle, the engine stops pulling plane's nose down so plane climbs faster.


It sounds a bit counter-intuitive but if you think about it, it all makes sense.


You may have to play with this a bit to get it spot on or close.


If you are using plastic engine mounts, you may want to establish the proper angle by using washers as you've indicated.

Once you know it, use a belt sander or grinder to modify the base of the mount so you no longer need the washers. Doing so will provide a larger mount to firewall countact area, that will not tend to wear through the wooden firewall, as the washers do.