I have a Showtime 50. When I knife edge...it rolls out. Why would it do this? Ive never had this happen on other planes before.

This is caused by a setup/balance issue. Exactly how does the Showtime roll out? Does it pitch toward the canopy, tail, or just roll badly with rudder input?

When you say roll out what do you exactly mean? Pitching as what Nathan says or is it the wings rolling or both on the lateral and horizontal axis? If its a little roll of the wings, that is normal you can mix it out or just manually sort it out.

If the plane pitches on the horizontal axis, means pulls to the canopy or tucks to the belly then firstly, its usually a CG issue. If it tucks to the belly then the plane is tail heavy. For tail heavy plane your elevator trim will be DOWN so in a KE it tucks to the belly. So if you pulls towards the canopy you know why.

If it affects on 2 axis, the lateral and horizontal then ... that usually means get another plane. Hehehehee ...

If plane is going from right to left....Pop into a KE with canopy facing you.... It will pull towards canopy and roll over towards you. Meaning high wing will roll over towards you. The more rudder...the harder the roll. I am used to having to hold with elevator...but never had issue with a plane rolling out. Plane is balanced as per specs. Now could this be a lateral balance problem? Any detailed info in diagnosing would be appreciated. Ive never had so much trouble with a new plane before. But they were all trainers and sport planes. Dont know if the type makes a difference.

Sounds like you need to move your CG back a bit.

How does the plane respond to rudder when its flat and level? Sounds like you have a little adverse roll coupling with the rudder. If it rolls with just rudder from flat and level flight, you have roll coupling. This is generally caused by the relationship between the rudder and the wing.

For example, if the rudder is high, it will tend to cause the plane to roll into the turn, If its low, it will cause the plane to roll away from the turn. Any dihedral in the wing will cause the plane to roll into the turn. Anhedral will cause the opposite.

If the roll coupling is not too bad, you simply correct for it with the ailerons. With computer radios you can create a mix that will help reduce it for you.

Nearly every plane I've ever flown has some roll coupling.

Brad

I cut my teeth on F3A models before computer radios were invented. The common cure to minimize knife-edge coupling was to change the dihedral of the wing. In your case the models rolls in the direction of the applied rudder, in which case I would say dihedral should be reduced.

Pitching towards the canopy in knife edge flight usually could be minimized by either moving the C.G. backwards or inreasing the angle of incidence of the wing (or both) and then retrimming the stab for straight and level flight. Pitching towards the belly can be minimized by the opposite actions. In severe cases I had to head back to the building board, either raising or lowering the stabilizer.

Nowadays most people use computer radios to mix out unwanted couplings.

more info here...when inverted does the plane climb? or do you need alot of push on the elevator to hold her level....the answer will let you know about CG...what happens when the other wing is low..in other words KE with the canopy away from you...

During inverted flight I barely have to touch the elevator to keep it level. BARELY! I tend to give it too much and do inverted climb. the plane is balanced right. Someone did mention Lateral balance to me. i wonder if this wold have an effect. im trying to figure out the best way to test lateral balance without having my fingers influence which way the plane will lean. Now as far as dihedral and incedence and all that.... Plane is a "pattern" plane. So there isnt any dihedral- that I can see anyway. Incedence...ummm no clue!

Just to clarify terminology - the Showtime is not a "pattern" plane, but is a 3D plane. The control surfaces are very large. Most pattern planes have much smaller control surfaces.

Now regarding your observations.

The pull to the canopy is caused by the normal trim of the plane for straight and level flight. To reduce this tendency, you can try increasing the wing incidence slightly by reflexing the ailerons down slightly. This may or may not help. If it gets worse, reflex the ailerons up slightly and see if that helps.

Get an incidence meter and check the incidence of the horizontal stab in relation to the wing. Are they the same? If they're slightly off, try to adjust them to equal.

For the roll out, does it always roll the same way (Opposite the rudder as described) or does it always want to roll to the left no matter which way you're flying KE? If it always wants to roll left, check that your elevators are equal. The pictures look like it has a split elevator. Are the elevators connected or controlled by separate rods or even separate servos? If they're separate servos, you may need to adjust subtrims to ensure they are deflecting equally throughout the travel.

You're best bet though is to do a google search and download a trim chart. Start from the top and work you're way through it.

Brad

What is being said here is accurate; however, may I step in and suggest you only modify ONE thing at a time. Properly setting up an airplane is a time consuming process and should be done fairly methodically. I would start by double checking the center of gravity. My bet is that it could still be moved back a little (from your descriptions of flying it). Almost everybody I know at the field flies their airplanes a little too nose heavy for some reason. I don't know if it's fear of making the airplane tail heavy or what, but they don't realize just how much better their airplane could fly. This won't fix the adverse coupling but should help or solve the pull to canopy problem. Once that is done THEN you can fix that by doing some suggestions given here.

if you are barely giving down elevator and are climbing in inverted flight then you are tail heavy..and that could very well be the problem...remember that the instructions only give you a starting point for CG...the true test comes in flight....I had an edge 540 that had some issues in flight..balanced per the instructions..was a hand full in flight..rolled her over and she climbed...fixed that and she is now one of my favorites to fly....