Why won't my plane fly?

[ouyin2000]

I know, I know. This is the thousandth time you've seen one of these threads. I've poured over the tutorials but for the life of me, I can't figure out why my plane won't lift off without ripping off the tail violently.

 

 

This should fly perfectly fine. It does in real life! I'm getting really frustrated with this...

[Vanamonde]

Sounds like you're having to pitch up so much that the tail is hitting the ground? KSP wings generate no lift at zero angle of attack. Try either rotating the leading edge of the wing up a bit, or adjusting the landing gear so that the nose sits higher. You will then generate more lift while rolling down the runway, and not have to pitch up so much to get airborne. 

[Alshain]

You appear to have no wings.  I see vertical stabilizers, and I think those are canards, but you need something to actually lift the plane.

You also appear to have no engines.  Can we get a birds eye view of this plane?

EDIT: OK, I just saw the shadow.  The wings are just deceptively hidden in that image.  A better screenshot would help.  However, I think your center of mass is a bit too far forward.  You could move the center of lift forward, but you also need to move the rear wheels up to the center of mass and that is going to make tailstrike worse.  I would remove the last fuselage and shorten the plane, see if that puts everything in the right position.

Ideally you want the CoL touching the CoM just barely, and you want the rear wheels just barely behind the CoM -OR- as Vanamonde said, angle of incidence on the wings.

Edited January 4, 2016 by Alshain

[Bandus]

I think the rear landing gear are to far forward. Maybe try moving them back a bit?

[Wanderfound]

It has very low ground clearance, a long tail and small wings. Perfect recipe for tailstrike.

Either give it more ground clearance, bob the tail, or reduce the AoA required for liftoff (by enlarging the wings and/or adding some angle of incidence).

You also have a nasty CoM/dCoM offset. The plane will become unstable as it runs out of fuel.

In general, though, see:

(FAR tutorial, but stock is close enough for the same basic ideas to work)

 

[Snark]

6 hours ago, Wanderfound said:

It has very low ground clearance, a long tail and small wings. Perfect recipe for tailstrike.

Either give it more ground clearance, bob the tail, or reduce the AoA required for liftoff (by enlarging the wings and/or adding some angle of incidence).

+1 to this.

Another option is to add a small landing gear mounted just under the tail, right at the back of the aircraft.  It doesn't even have to touch the ground when the craft is sitting on the runway.  (In fact, it's probably better if it doesn't touch, so that it doesn't hamper your rotating off the tarmac.)  When the craft rotates up on takeoff and tries to strike the tail on the ground, that extra gear will touch the ground instead and save the tail from going boom.

It's not an especially elegant solution (you're carrying around the extra weight and drag of that landing gear all the time)-- more of a band-aid than a real engineering answer.  However, it's simple in that it requires no rearranging or redesign of your plane.  Wanderfound's suggestions would be better, but if you're having trouble with those, the "extra gear on the tail" option is one more tool in the toolbox.

Edited January 4, 2016 by Snark

[Val]

Like @Wanderfound and @Snark mentions there are different ways to solve the ground handling issues you are experiencing.

I will shamelessly plug my own A-1 Pioneer which looks to have a similar mission profile and tech requirements. You can study it with regards to CoM, CoL and landing gear positions compared to your own.

Link includes flight instructions and videos.

[Rocket In My Pocket]

An early career science gathering plane I used, it's designed to take off and land in rough terrain with limited running room.

It's a good example of another way to keep your tail and control surfaces up out of harms way.

I know it looks funny, but it flies beautifully! Lol.