I've spent the past three hours committing a genocide of historical proportions against my Kerbals, and it's making me quite sad.
Valentina would really appreciate if I could get my airplane off the ground, but it keeps exploding on the runway by the exact same failure mode: The plane veers to one side or another, either I or SAS correct it, which starts a left/right wobble, which builds until one of the wings hits pavement, at which point the craft quickly brings Valentina to her untimely end.
I've covered all my bases, as far as I can tell:
- All three wheels (one steerable in front, two fixed in back) are mounted with angle snapping, symmetrically
- Wheels are mounted to the fuselage, rather than to the wings (which flex under load)
- Wheel base is wide
- Center of lift is behind center of mass, and slightly raised
- Rear wheels are in front of tail, but not enough to make tail strikes easy
- The two engines have been mounted every imaginable way with the same result: Over the wings, on the fuselage, on girder segments, on the wingtips, etc.
- Wings have been flown both with and without struts
- Wheel friction was even decreased to 0.3 for front wheel and increased to 2.0 for rear wheels, as per a tip found online
It seems if I turn off SAS, I can prevent the oscillation from starting as it's initiated by some control input, whether from me or SAS, but then the plane veers off the runway until it hits something. Intriguingly, there is one thing I've found that does prevent the wobble from starting, and that is to use a single engine mounted directly on the back of the fuselage, which prevents using a tail and is ultimately a fairly significant restriction to build around.
I've spent some time scouring the internet for ways of solving this problem, and found a number of pieces of advice on preventing wobble and improving planes in general, some of which made it into the above list, but Valentina's still dying, and I'm tired of Kerbal funerals.