Large aircraft/spaceplanes made from MK3 parts tend to disassemble themselves on the runway.

[Jakalth]

I have tested 3 different, stable, aircraft made from MK3 fuselage parts and normal wings. All 3 aircraft are unable to be launched from the runway due to the MK3 parts simply detaching themselves from each other during taxiing, and sometimes even earlier during the moment the physics are turned on before launch. All 3 craft were able to survive hard landings prior to the 1.0 release and in the SPH, and show no errors or suggestions from the new helper, meaning they should be completely fine.

Any craft I have, that are made from MK1 or MK2 fuselage parts, have no issues flying in version 1.0 other then having far too much thrust now, if using the turbo ramjet engine(which they already had equipped prior to the changes), due to the new engine settings(not a bug).

Not sure why this issues has arisen, unless it is due to the changes in part physics breaking the craft saves??

[Supernovy]

A screenshot of the crafts in question would help diagnose the issue.

Mk3 parts do have lower breaking tolerances than expected, but your choice of landing gear may exacerbate the problem. A screenshot would clear this up.

[Laie]

If they still break so easily as in 0.90, this is a bug and should be reported as such. Same with the harsh physics onset.

[Jakalth]

Ok partly solved the problem with the MK3 parts. Was tied to 3 different things which made it difficult to spot initially.

1: Landing gear: Old craft files used small landing gear bay as their landing gear. Only they used a lot of them. This was the cause of one of my craft disassembling on the runway.

2: Engine thrust: The changes too the Turbo Ramjet engine have made it far more powerful then it used to be. At full throttle, which was needed just to get the aircraft off the ground in 0.90, was causing the airframe and wings to Overspeed. Instant disassemble was a result of too much aerodynamic forces being applied to them. Taking off at reduced throttle, before reducing the number of engines used, resulted in successful flight.

3: Takeoff angle: Three of the craft I tested required inefficient landing gear placement due to bomb bays(cargo bays facing down). This placement makes it hard to get initial liftoff without pulling up hard at the end of the runway. With the increased speed due to the much more powerful engines, the aircraft pitch up quicker then they used to. If allowed to pitch up to quickly, the wings receive an aerodynamic "kick" from the high angle of attack. This kick is enough to knock loose some of the wing segments which cause a domino effect on the rest of the craft causing unexpected disassemble. Keeping tighter reigns on the stick and risking a bump and go takeoff, prevents high angle of attack on liftoff and keeps the craft intact. But that aerodynamic kick is really deadly for large multi segmented wing aircraft....

I also ended up with the game crashing when the craft was unable to make a smooth landing on the runway and was destroyed. The moment the craft flew apart, the game locked with the sound of the explosion playing in a loop and stopped responding. Had too alt tab out and force close it. There is no error report given for this crash... wish there was, would make it a bit easier...

My effective bomber for a challenge, most of it is cargo bays. Was rock solid in 0.90. Harder to fly in 1.0

Edited April 29, 2015 by Jakalth

[Claw]

The game always creates a log file, even if it doesn't crash. In the windows version, it's located in KSP_Install/KSP_Data/output_log.txt

If you want to toughen up the joint strength on those Mk3 parts, you can try my stock bug fixes for now: http://forum.kerbalspaceprogram.com/threads/97285

Cheers,

~Claw