I have a problem with the russian aircraft in the FC3 module (F-15c is fine). THe Su-27 Flanker pulls up all the time. As if there was some input on my joystick. I have a X55 HOTAS and it is not the problem.

Why are all the russian aircraft in FC3 pulling up by default?

Have you tried using trim?

I can trim it out but the weird thing is the f15c is fine.

THe default settings for the su 27 are.

Well, that's your problem right there: It's trimmed back a good part. Not sure why as I've only tried the Flanker once (not a fan of the FC3 planes), maybe it's a pre set takeoff trim?

F15 flight system trims for you while Russian aircraft do not.

Aircraft fly like the flanker does in reality. You must trim for the speed you're flying at.

Speed increases, the center of lift moves and the aircraft 'pulls up'. Speed decreases, the center of lift moves, and the aircraft 'noses down'. It will fly like this constantly, it's called a phugoid pattern.

The F-15C's flight control system tries to maintain 1g (among other, very useful things for combat), so it's trimming the aircraft for you.