Getting planes off the ground?

[Jokurr]

So I’ve been experimenting with a variety of different planes lately that serve different purposes, and I find that a lot of my larger designs (but not THAT large) have a hard time getting off the ground. Once they are in the air they control just fine, but for some reason they are reluctant to become airborne. What usually happens when I take off at the KSC runway, is that I pitch up the whole time with nothing happening, and then at the end of the runway, there is a little bump in the ground that gets me a few feet off the ground and from there I never have an issue getting into the air (assuming the tail of my plane doesn’t smash into the ground, which has been known to happen).

Is there some trick to generating lift while you’re on the ground? Realistically I know large airplanes rely on flaps to generate the required lift, though I’m not sure how to design this in game or if it is even necessary. Seems silly to have to rely on bumps to get planes into the air, so some tips are appreciated.

[SecondGuessing]

An image would be handy.

It sounds like you issue is the angle of attack when on its wheels. Try setting it up so that it rests on its landing gear with the nose up slightly, that may help.

[BobTheYoungFish]

Messing around with the place of the landing gear can help. As SecondGuessing said having the nose up a bit can help. Having the rear gears not too far back seems to help as well.

[Jokurr]

Thanks, I'll try moving landing gear. I guess an ideal place would be just behind the C of M / C of L, just enough so the plane doesn't tip over when it's on the ground?

[katateochi]

with rockets it's MOAR boosters, with planes it's MOAR wings! Also getting the right balance of COL and COG counts for a lot, but with larger things, they just need more lift. Having some control surfaces toward the front can help, depends really on just how big the thing is.

Largest plane I made was this, just had to keep extending the wings till I got enough lift. There prob is a more elegant solution, but this was the brute force method of MOAR that eventually worked.

[Qumefox]

The more 'elegant' solution would have been to reduce weight instead of adding more wings. Generally being unable to get a plane off the runway usually means you have insufficient lift for the plane mass. You have two options. Add more wings, like you did, or make the rest of the plane lighter.

[Pulstar]

It's because landing gear becomes massless when you're airborne. While it's touching the ground it has the 0,5 tons of mass each as listed in the VAB/SPH. So it becomes lighter and thus it can actually fly.

[gompasta]

A tip is to place your rear landing gear as far forwards as possible, to allow for it to pull up easier.

[Brotoro]

It's because landing gear becomes massless when you're airborne. While it's touching the ground it has the 0,5 tons of mass each as listed in the VAB/SPH. So it becomes lighter and thus it can actually fly.

That would be a very strange behavior... Why does it do that? Do rocket landing legs behave the same way?

[UmbralRaptor]

It's because landing gear becomes massless when you're airborne. While it's touching the ground it has the 0,5 tons of mass each as listed in the VAB/SPH. So it becomes lighter and thus it can actually fly.

I'm fairly certain that the smallgearbay part is massless in all situations outside of the VAB/SPH. ...though this seems like it would be easy enough to test...

edit:

That would be a very strange behavior... Why does it do that? Do rocket landing legs behave the same way?

As best I'm aware, it's something about the part type (compare with struts, fuel lines, and 0.10 - 0.17.1 RCS blocks). Landing legs have normal mass.

[katateochi]

It's because landing gear becomes massless when you're airborne. While it's touching the ground it has the 0,5 tons of mass each as listed in the VAB/SPH. So it becomes lighter and thus it can actually fly.

I'm fairly certain that the smallgearbay part is massless in all situations outside of the VAB/SPH. ...though this seems like it would be easy enough to test...

Yeah, just tested. I was so surprised by what Pulstar said I had to check it out.

As UmbralRaptor says, they have a mass in the VAB/SPH, but loose it as soon as you get outside. Lifting them off the ground does not cause a change in weight.

Made this silly craft, without wheels it was 5ton. with 4 wheels it was 7 ton.

Launched it and straight away its mass was back to 5 ton. Lifted wheels off the ground, still 5 ton.

(science is great)