Aircraft Flight Dynamics Troubles

[nabeav]

Hi all

I recently started dabbling in KSP aircraft. However, the flight dynamics are frustrating me to say the least. I'm an aerospace engineer irl and all of the things that /should/ contribute to aircraft stability seem to have no effect.

I built an aircraft with the following characteristics:

- Main Wing on top of fuselage. Slight positive dihedral angle. This should give inherent roll stability.

- Horizontal tail with negative angle of attack in conjunction with COL behind COG should give inherent pitch stability.

- Vertical tail of ANY KIND even with no control surface should give inherent yaw stability.

However, after I takeoff, my aircraft starts randomly yawing/rolling. This should NOT be happening. Everything is symmetric, and I'm using winglets for my empennage (tail) control surfaces to make sure the control surfaces aren't off-centered.

Is this just the nature of KSPs flight engine? Or am I missing something obvious?

[OdinYggd]

KSP's implementation of aerodynamics is very minimalistic and horribly flawed- such as control surfaces being capable of producing infinite thrust in the so called infiniglide phenomena.

You'll probably be much more comfortable flying using the Farram Aerospace Research (FAR) mod, which revamps the stock drag model and aerodynamic behaviors with one that is much more realistic.

Center of lift behind center of mass usually works, although the control surfaces are too aggressive and lack of good feathering support means the craft will usually overcorrect and show symptoms of a fugoid cycle when flying- although this disappears on heavier craft because the increased mass helps dampen it out.

I've yet to notice any benefits from diehedral on my craft, but KSP does seem to respond best to canard and delta type wings over conventional arrangements.

Biplanes and triplanes fly well in KSP too.

[Eric S]

Correct. The current aerodynamics model is a placeholder that is intended to be replaced at some point.

A few months ago, "at some point" was looking like we'd see the first pass in 0.19, but the devs changed their development cycle to something a bit more agile (more updates, but smaller updates) and we didn't get any of it then. I'm still hoping to see it soon, as I didn't want to start experimenting with spaceplanes until we got the new model so that I didn't have to relearn everything when it all changed.

[TheHengeProphet]

If default aerodynamics bothers you, I suggest using the Ferram Aerospace Research mod.

Link:

http://kerbalspaceprogram.com/ferram-aerospace-research/

Good luck!