[SOLVED] Plane bounces and either: i) explodes on runway during spawn or ii) Blows up as I gain speed

[Unit 45]

I'm going head over heels as to why these happen and I've even watched some tutorials.

http://steamcommunity.com/sharedfiles/filedetails/?id=842782241

http://steamcommunity.com/sharedfiles/filedetails/?id=842782298

http://steamcommunity.com/sharedfiles/filedetails/?id=842782439

http://steamcommunity.com/sharedfiles/filedetails/?id=842782503

http://steamcommunity.com/sharedfiles/filedetails/?id=842782586

http://steamcommunity.com/sharedfiles/filedetails/?id=842782732

Thanks to all those that helped but this thread solved.

[Zantonny]

The engine you're using is a rockt engine. The thrust given out is just way too muc for te small weight of the plane. Switc to one of the jet engines (That requir intake air)

Do your wings have elevons on? If not, be sure to attach them, then pull your wings slightly forward so your centre of lift is inside, but slightly further behind the centre of mass.

[Unit 45]

Originally posted by Zanton:

The engine you're using is a rockt engine. The thrust given out is just way too muc for te small weight of the plane. Switc to one of the jet engines (That requir intake air)

Do your wings have elevons on? If not, be sure to attach them, then pull your wings slightly forward so your centre of lift is inside, but slightly further behind the centre of mass.

Does that explain why it bounces on the Runway? Also, the rear wheels, not sure what they're called, are quite long and may not be leveled with the front steering wheel. Is that the problem?

[Zantonny]

It bounces on the runway because youve no manner of controlling drag, your relying on the engine completely. I am actually suprised your plane doesn't just launch, do a flip and crash into the ground.

[Unit 45]

Originally posted by Zanton:

It bounces on the runway because youve no manner of controlling drag, your relying on the engine completely. I am actually suprised your plane doesn't just launch, do a flip and crash into the ground.

No I mean bounces on the runway when stationary, directly after spawn. Even with the brakes on it just bounces like crazy. As I start the engine and increase throttle it just face plants and explodes :D

[George Kerman]

There are many things to point out, obviously what Zanton said is correct as well so I wouldn't repeat that.
1) I think the front wheel is not aligned with the back wheels, the front one looks to be higher. When the plane spawns on the runway, it is slightly dropped from the air. If you have improperly aligned wheels at different heights, then this bouncing is more pronounced. You should also rotate the back wheels so that they actually touch the ground at a 90 degrees angle. Did you see how those wheels look? Image those wheels and how they look on a real car/plane/ whatever.
2) Don't use the level 1 runway. It sucks, just steer left or right and take off from the grass. The level 1 runway has many bumps that can affect your take off.
3) Add some wings in the front of the plane if you have significant issues taking off. That same wing type that you used as tail fin can be used as canard in the front of the plane. Obviously you'd have to adjust your center of mass and its alignment with the center of lift afterwards.
4) Don't add a very big amount of fuel. For example, 800 units of fuel on a plane with 2 Juno engines can get you at least halfway around the planet. If you add a very big amount of fuel you might not be able to take off properly. This wasn't it in your case, because you had a Swivel or Reliant engine.

P.S.: By the way, I didn't see the SAS activated in your screenshots! Dude, press T and activate SAS before every launch!

[George Kerman]

Anyway, the most important thing is, keep trying! I assume this is your first aircraft model. My first try was completely unsuccessful, then returned a few times and finally I got a plane to take off. All those initial issues had to do with wheel alignment and the symmetry mode (I saw in your screenshots that yours is OK), so focus on getting them wheels aligned. First you have to be able to reach 30m/s (ish) on the ground without any explosions/ without any uncontrollable steering so that you can take off. Then you gotta have sufficient lift to actually take off. Focus on the first step and then add some canards/ lose some fuel to actually reach flight.

[Zantonny]

My planes are stupid, but they work!

http://steamcommunity.com/sharedfiles/filedetails/?id=842235301

[Zantonny]

Originally posted by RoofCatA:

your plane is too heavy for first wheels. Up to 5t recommended. Get next wheels.

Funny thing is sometimes the wheels go crazy while sometimes on a very similar plane they won't. There are just a few bad things in KSP. Wheels and Runway are two of them. When they meet, uncool things happen.

Don't make planes with rocket engines. It won't work well. Too wastefull for anything.

My runway has a hole in it..

[Zantonny]

Originally posted by RoofCatA:

your plane is too heavy for first wheels. Up to 5t recommended. Get next wheels.

Funny thing is sometimes the wheels go crazy while sometimes on a very similar plane they won't. There are just a few bad things in KSP. Wheels and Runway are two of them. When they meet, uncool things happen.

Don't make planes with rocket engines. It won't work well. Too wastefull for anything.

http://steamcommunity.com/sharedfiles/filedetails/?id=842866919

Literally.

[Mr. Fusion]

Building airplanes is super finnicky in KSP, I kinda hate it, TBH. Moving parts around on the plane just literally by a few pixels can mean the difference between a plane that flies and one that does things real life physics would probably shake its head in disdain at.

While others have pointed some of these out already, still:

- Rocket engines + rocket fuel tanks are just too heavy for the landing gears you are using. They are likely to get overstressed and explode, if not right on vessel load, then when you start accelerating.

- Too much vweight on a wheel can result in uncontrolled oscillation/bouncing. You can offset that somewhat by experimenting with the spring and dampener values in the right click menu of the wheel.

- The "CoL should be aligned with CoM" rule you find in airplane building guides doesn't always apply. In fact, I found that most planes fly stable when the CoL is set to... wherever it needs to be set for that specific design, which can be pretty much anywhere. The only way I found to find the right spot is trial and error, adjust it in tiny steps by moving lifting surfaces around and test the plane until you find the position/configuration that actually works for that specific one.

- Wheel physics are still bugged, especially when using the smaller wheels. I've gotten wheels randomly doing all sorts of stupid things on airplanes which other times were behaving as expected.

- The starting runway is useless, it's so bumpy that it'll cause smaller wheels to overstress and explode. Even if that doesn't happen, all the bouncing your plane will do while trying to gain speed will likely destabilize it to the point where it becomes uncontrollable and crash. Just roll off the runway to the left, move away a little, then point towards 90 deg (same heading as the runway) and take off from there. Do the same for landing too, don't use the runway, it's near impossible to keep a plane intact.

- SAS can sometimes be more hindrance than help. Depending on the plane design, sometimes having it turned on will actually prevent the plane from taking off, as SAS will do its best to keep it on the ground (thinking that's the desired stable position it needs to maintain) until it explodes. Other times, if the plane has enough starting AoA to overcome SAS, it'll "panic" when sensing that the plane started tilting up and immediately faceplants it into the ground. You have to experiment with SAS both turned off and on with each plane design to see which case is it for that specific plane. Once you are in the air, no part of the plane is touching the ground and you have a positive RoC, SAS behaves better and should be safe to turn on even in cases where it would sabotage the takeoff.

[Docsprock]

Your rear(Main) landing gear needs to be spread more. They are cambered inwards too far.(use rotate tool).Then move them forward a half-meter to be just a bit behind COM. The nosewheel is backwards.

RoofcatA may be correct about the weight, but I think I was able to launch a very similar craft. The bouncing on spawn is normal, but it shouldnt destroy your craft. So, remove a bit of fuel to take the weight down.

[howardsheard]

http://steamcommunity.com/sharedfiles/filedetails/?id=840322252

http://steamcommunity.com/sharedfiles/filedetails/?id=840322079

http://steamcommunity.com/sharedfiles/filedetails/?id=840322233

you need to make your plane v light using just the basic engine in the first picture note:

1. the two central tanks are empty
2. how the centre of lift is just behind the centre of mass
3. i have put 2x2 small liquid full size 0 fuel tanks full on the end of each wing
4. i have put a small air intake also on each wing
5. the tail fin only controls yaw, the outer flap roll and pitch and inner flap just pitch

edit if the runway is too bumpy it is worth it driveing slowly off and using the grass

http://steamcommunity.com/sharedfiles/filedetails/?id=840327442