Planes just sink into the ground...

[Zorlond]

I've been having trouble with landing some of my planes. Not all of them, mind you, just some of them.

Imagine this: I'm about 2k above the ground (MechJeb, so I know where the ground is), I flatten out, cut the throttle, and start my descent. I tug upwards now and then to keep my descent sane, yank hard when I pass 500m to flatten out and check the area ahead for surface oddities. Lower landing gear, hit the lights if I'm still not sure of the landing area, then ease my way down while keeping my nose up. My wheels come down and kiss the dirt...

No, wait, they sink right into the dirt, followed by my entire plane, which then explodes in one ball of fire when the cockpit passes the surface. From wheels touching to explosion takes 3-4 seconds. That's how gentle I'm coming down. It literally looks like a 'hole in the world' bug, right before I go boom.

I quickload to the same spot I just described above. Try again. Boom. Try again. Boom. Turn a few degrees to the right, try again. Boom. Turn a few degrees to the left. Boom. Power up, U-Turn, try again. BOOM.

My last flight like this, I was coming back to base after a couple survey missions. I just kept crashing into the ground outside the base, no matter how gently I tried to touch down, both vertically and horizontally. It's like the ground and my wheels just couldn't meet.

Here's the kicker: In desperation, I tried the one thing I tend to avoid. I aimed for the landing strip at base. I've always been terrible at lining up for landing strips, but I figured if any part of ground HAD to exist, that'd be it.

I hit the landing strip harder, faster, and more crazily than I'd hit any ground in all my other landing attempts, with engines screaming trying to pull out of a kamikaze dive (I told you I was terrible at aiming at strips). I actually landed. Wobbling back and forth, brakes screeching for half the runway trying to stop before taking a swim. Managed to stop. Perfectly intact, in a landing that was the worst I'd ever attempted.

The ground doesn't exist for my most gentle of landings, but the strip takes a terrible landing in stride and lets me go without a scratch. *grumph* >:(

[Roadkill]

This is pretty much why I designed a rover to do things on the ground, then built a detachable delivery system to it. Get to where I need to be, shut off the jet engine, then cut it loose while activating the parachutes for the jet portion, then parachute the rover to the surface to do what I need to do.

Landing sometimes can be a nightmare, especially after you've flown for 30+ minutes just to have something happen on landing. Of course, what you're describing seems to be something different altogether.

you may want to try adding parachutes to the back of your jet and testing it that way. place at least 2 chutes on your place at equal distance from center of mass and see if it still does it.

Out of curiosity, how fast are you moving when you hit the ground?

[Zorlond]

Originally posted by Roadkill Eatin' Hick:

Out of curiosity, how fast are you moving when you hit the ground?

Horizontally, about 50-60m/s, vertically, not sure when wheels actually touch ground, but I try for as low single-digit as possible.

[Toastie Buns]

Do me a favour, copy/paste your ship into a new save and see if the problem persists. I have a feeling you got unlucky with your world generation and it decided to be a proceedural ♥♥♥♥♥♥♥ to you.

[Zorlond]

Alright, copied the design over to a sandbox game I use for testing mods. Flew around a bit, had very hap-hazard results again. Sometimes I sink into the ground, sometimes I land, sometimes the game 'changes it's mind' and has my plane sink into the ground right after my wheels successfully touch down. Had MechJeb take a turn landing at the Island Runway, it managed it with minimal trouble, couldn't tell MechJeb to land at random spots on the map, though.

So now I'm thinking something's wrong with the plane design that I can't see. So, take a look:

http://steamcommunity.com/sharedfiles/filedetails/?id=390489980
http://steamcommunity.com/sharedfiles/filedetails/?id=390489963

[Toastie Buns]

Can you upload the file please? I'll throw it in the SPH and see what I can do. I have a theory that it's the wheel angle coupled with some other things but I'd need to experiment (ie; crash repeatedly)
Merely building it myself may lead to differences.
Dropbox, sendspace, any file uploader will do.
(Your files are located in KSP>saves>SPH just in case you didn't know)

[Zorlond]

Think I *might* have found the problem. I did mention I try out mods from time to time? I keep a backup copy of vanilla KSP on hand, just in case I bork something up with mods. Apparently I did. I took a plane up, did a quicksave near a land survey site and tried to land. Obviously, I crashed when my wheels wouldn't touch ground. So, leaving that quicksave intact, I exited and copied all the backup files over the play files, overwriting when needed. (note that I did previously attempt a Verify Cache with Steam and that did nothing for the issue)

Went back in, loaded the quicksave, and successfully landed on the very first try. Might've been a fluke, I admit, and I'll probably come back here if it turns out to have been a fluke.

I tried out some realism mods a while back, wasn't wild about them, and took them out. They might not have come out as clean as I had hoped.

[Toastie Buns]

Well, at least the women and children escaped safetly. Now at least we can rebuild the town!
Huzzah!
Good luck with the rest of your planes, OP. I noticed you were the poster who made the sideways flying jet, maybe just stick to rockets?