[question] How to reduce lateral slip?

[SteevyT]

So I made an aircraft using c7's flight mod. It flies fairly well, I can control it most of the time. However, it likes to slide sideways through the air. I know that putting more vertical fins on it should help, are there any other tips on how to reduce slip?

[Herra Tohtori]

Set control forces to zero in the command pod's cfg file, and fly the aircraft with control surfaces only.

Then make sure that the centre of gravity is ahead of the centre of pressure in both horizontal and vertical plane.* That should make the airflow itself automatically straighten out your ship - although you'll need to dampen any harmonics such as dutch roll manually with control inputs.

*Centre of pressure means the centre of the sum of aerodynamic forces acting upon an object as it flies through the air. If the centre of pressure is behind centre of gravity, the object is dynamically stable and will right itself after being deflected from a straight path through air.

Practically this means: Yes, you need to put vertical stabilizer to the rear or the craft, typically as far rear as you can to achieve best results. If you need more yaw control force, then you might want to use two vertical stabilizers, each with their own rudder. That will stabilize the craft in relation to yaw axis.

Same principle applies to pitch stability and, to some extent, roll stability. Roll stability is achieved by putting the wings above the centre of gravity with means of dihedral angle or simple wing placement such as in Cessnas and many other general aviation designs.

However, pitch and yaw stability are far more important in my opinion than roll stability.

[Tiberion]

What causes the snapback on pitch control? Like when you pitch up and it bounces back halfway when you release?

[Herra Tohtori]

What causes the snapback on pitch control? Like when you pitch up and it bounces back halfway when you release?

That exactly. Stability. You're using control forces to deflect the ship from the position it wants to be at in relation to airflow. When you release the control forces, it starts to swing back, and it enters a harmonic oscillation around the balance position unless you prevent that.

This is why analog controller > digital controller in atmospheric flight. And in flight general.

Get a joystick or gamepad, then when you use elevators or rudder, gradually let it move to centre position which prevents the craft from entering a pilot-induced oscillation (which is what happens when you try to correct the 'snapback', but you overdo it, and it swings back to another direction). This is easiest to prevent with analog controller, and smooooth hands with control inputs.