I have a Superstar .40 (Flat bottom trainer) I fly occasionally and I've noticed that when I put it into a turn, the tail actually drags/sags unless I pretty much make it a knife edge turn. The plane is nose heavy, but I don't see how that could make the tail sag. When it turns it looks like the tail weighs a ton and it just being dragged along by the engine. I would think it was tail heavy but I KNOW that it is in fact a little too nose heavy if anything. Any ideas on what might be causing it or how to correct it?

Thanks,
Rick

The wing must generate additional lift through the turn in order to both support the wieght of the plane and turn it.

To do that, assuming constant speed and altitude through the turn, then the wing must fly at a higher angle of attack. Hence, you see the tail drop. That's why we must provide some elevator input to maintain altitude through the turn. That's normal, there is nothing to correct.

If you don't like seeing the tail drop, you could simply fly faster through the turn to make up for the elevator input (AoA increase) that you'd normally need to feed in order to maintain altitude. So, perhaps just give a bit of throttle as you enter the turn and reduce it as you level out.

Sounds like adverse yaw, caused by the outside aileron dropping too low creating too much drag. The cure is what they call differential ailerons; set up the ailerons so they go up more than they go down, probably about a 2:1 ratio. When using one aileron servo, use a wheel or six-arm output arm on the servo and move both pushrod attachment points forward so they are no longer straight across from each other...JIM

rik756, Does this tail sag happen during the roll (i.e. while you are holding the aileron input) or when you center the ailerons and are banked in the turn?
In absence of differential aileron throw you can also add a bit rudder to overcome adverse yaw.

The stick on the left side of your transmitter moves fore and aft for throttle, and, beleive it or not, it also moves left and right for rudder.

Rudder is used to yaw the airplane. You can get by without usng the rudder, bur your turns, especially at lower speeds will always look funny without it. Try holding a little rudder in the direction of the turn and watch what the tail does. You may have to neutralize or even put in opposite aileron to maintain your bank angle. I'm a big advocate of learning rudder inputs as you learn to fly rather than after you've learned to fly with Ail/Elev only.

Richard

rwlewis is on the right track. By all means learn to use the rudder, however use it only when rolling into and out of turns. Don't hold rudder during the turn. That will produce a skidding turn. Rudder is generally required to counteract adverse yaw (which is the tendency to yaw away from the turn caused by deflection of the ailerons) and is only needed when the ailirons are deflected. It is not needed during the turn.

Does it do the same thing in both directions?

If it's only in one direction then you've got your rudder and aileron trims crossed up so that one is compensating for the other being out of kilter or your wing has a warp and you are using the rudder to compensate. Any off balance trimming such as this can do what you describe but only in one direction. The other way should be fine or look like the opposite.

If it is the same to both sides then there are two things you can do. First is learn to use the rudder as rwlewis suggests and the second is that the vertical tail may be too small on this design. The tail sagging in the turns is often a sign of the vertical tail area being a bit small. This also shows up as a tendency to respond to adverse yawing during aileron use.

Another possibility is that your aileron linkages are set up in such a way that you have reverse differential to what is desireable. If your down traveling aileron defection angle is more than the upward deflection angle you will get adverse yawing despite having a lower aspect ratio than a glider. Often times the linkages are installed as convienient without realizing that you have to check for that sort of side effect.

Good point on not holding the rudder during the turn - especially on a somewhat neutral plane that stays banked after aileron input. However on a very stable plane like some trainers, you have to hold the aileron to maintain the bank angle, therfore you would also hold a little rudder to counteract adverse yaw. The slower you go, the more you should steer with the rudder and less with the ailerons.

So basically, you are still only applying rudder at the same time as the aileron input for a coordinated turn. Just move both sticks at the same time, in the same direction.

I cringe when I see guys making the last turn on final with a trainer going very slow and having to bank the wings to 45 degrees and pull elevator to make the turn onto final heading, then full opposite aileron to level the wings, with associated adverse yaw - pretty hairy and will only teach you to snap that Extra 330 that you are going to buy as a second plane into the ground in a heartbeat.

The alternaitve is adding a little rudder coordination and banking to only 15 degrees or so and making a much more level turn onto final and making a nice non-busy approach.

Richard

Good advice on the landing piloting there RL. Those are hard things to learn and easy to forget.

Also it occured to me that adverse yaw is at it's worst if the model is operating at higher angles of attack as in flying slowly with the nose up towards the clouds. If a bit more power and speed is used the wing is not flying at so high a AoA and should be more tolerant of aileron usage in this regard. But if the yaw is bad then a bit more speed won't help much. I'm thinking of small amounts only.

A trainer type with a lot of dihedral still doesn’t require rudder (and ailerons) held in a coordinated turn. It will only tend to roll wings level if a sideslip into the turn develops. This inevitably is the result of not enough elevator held in the turn causing a slip to the inside. If the wings are banked, and elevator is applied, there is normally no need to hold aileron and rudder during a turn, even with a trainer.

With a Hobbistar or Avistar I might have used a little rudder now and then but this plane I don't think I've touched it other than on the ground for roll out.

Jimtrainer,
It's usually it most evident when I enter the turn holding the ailerons in the turn. It's an Irvine .61 on a 40 trainer. That wasn't really intentional but it flew beautifully on an Avistar so instead of buying another engine I just moved it to this plane. (the avistar died due to radio failure).


BMatthews,
No it's not the same in both directions. It does it very little to the right, but very pronounced in a left turn while holding aileron in the turn. You mentioned having the having the trims crossed up. If everything looks normal (level) on the ground how else would go about checking if you actually had one trim figting another?

michpittsman,
You said, "When using one aileron servo, use a wheel or six-arm output arm on the servo and move both pushrod attachment points forward so they are no longer straight across from each other...JIM" I'm not sure I completely understand what you mean here. If the attachment points are not the same, would it not then give me different turn characteristics in left vs right turns?

Thanks for all the great replies. I have several things I'll check now. I loved flying the other two planes but I really don't even like flying this one due to this tail sagging thing. This is actually a plane for my wife, but she hasn't Hopefully I can get it corrected so I can enjoy it too... Or better yet I'll have my stinger done soon and fly it instead lol.
Rick

rik756-When the pushrod attach points are both forward, the up aileron will go further up than the down aileron will go down, regardless of which way you are turning. Differential is most often used to advantage on flat bottom wings...JIM

The simple way is to do it in the air. Add some rudder trim towards the direction that it hangs the tail low when turning. So that would be left rudder if it drags the tail in left turns. You're adding rudder trim, or rather REMOVING BAD rudder trim to pick up the tail. Then use a bit of aileron trim to compensate for the trim change of the new rudder position. Do this a bit at a time until the model turns equally in both directions.

That should do the trick as long as there isn't something else amiss. With that oversized engine I'd do all this at idle or just above. Then power up and see if you need any engine offset to compensate for the torque. You may be using the rudder to hide an engine problem and it's resulting in your tial sag problem.

people buy these things as a second airplane?? i have had many many many airplanes.. and i had the chance to fly an extra.. i hated every second of it. and yes it was set up properly and set for "tame" flights. i think its easier to fly a helicopter than an extra.. [:'(]

anywho.. back to the topic... THE RUDDER IS YOUR FRIEND!!! LEARN TO USE IT , BUT RESPECT IT ALL THE SAME! JUST A LITTLE TOUCH WILL GO A LONG WAYS!