my fast plane hits the problem when going at 2000mph, I would have an unexpected and unwanted roll and if it goes too fast it would shatter

@17yearsold says the one with only 30 prestige

When you mirror sometimes one side has more drag points

A second way you can counteract the roll is to add a few degrees of pitch on one elevator, which will cause an opposite roll moment to counteract the problem roll (this is known as "trimming" in real life--actual aircraft go through a "trimming" procedure post-maintenance being performed on flight control surfaces). I did this on my A-4K when I had induced a roll through my lack of understanding of the SP attach-nudge-mirror problem. The only problem with this is that the build is then trimmed up for a certain airspeed and altitude (low altitude and approx 480 mph for My A-4K--I figured the average SP player flies at full throttle and low altitude, so most players would not notice) but changes in those parameters will reintroduce a roll due to changing aerodynamic forces.

@LockheedMartinAerospace, you are correct: All of the factors you describe will induce a roll. However, SP also has the simulation issue I describe below, which does not exist in "real life". The "real life" factors you describe are usually much more evident, causing a much more violent roll than the slow, annoying roll problem many builders suffer.

There are a variety of answers below, but @BogdanX is correct: The roll is caused by attaching a fuselage block to one wing, NUDGING the block into the desired position, then mirroring the block to the opposite wing. My theory is that, when nudging, then mirroring, the mirrored block will attach to a different attachment point, the closest point, which is different from the original side. That throws off the balance and induces the roll. My technique for avoiding this is to attach the block to one side, then mirror without nudging first. Once created, THEN nudge both blocks into position. Be sure to check (with Fine Tuner) the final position of the blocks to ensure they are exactly symmetrical. You can also manually place blocks on both sides without resorting to mirroring, though it is tedious to ensure both sides are placed in exactly the opposite positions using the same attach points, it's not too terribly difficult.

@LockheedMartinAerospace thanks!

@Hyperloop It happens usually because of 3 things. One, imbalanced weight, usually insignificant if making replicas. Two, imbalanced lift. Three, imbalanced thrust. The last two you have to pay attention to, though number three is very rare. Two is very common either because of one wing being larger, different angles, or different airfoils.

@BogdanX Thankyou, and I found out that putting more vertical stablizers helps a lot

@Hyperloop I'm not getting it but in about an hour I can use my PC to test

El glitchio that can't be solved

@MechWARRIOR57

AG1 turn on the afterburner

Try this out
https://www.simpleplanes.com/a/19sL91/TLZ-Army-VT-90-Verti-Invader

never seen it