Yet another landing gear issue thread

[stormdot5]

Hi guys, I've been having trouble with runway rolls using non-stock landing gear.

I've been trying out the early game avoiding rocket launches. To do this I'm using FAR, spaceplane plus, and some firespitter landing gear. This lets me build some planes without having to go to space first for loads of science.

The issue is that when my planes get up to speed they veer off/tip and clip a wingtip resulting it rapid unplanned disassembly. I've experimented with different configurations but I can't work out the problem.

Here's a pic of an example plane I think should work fine:

It uses firespitter landing gear with skids at the back. The gear is mounted the the top of the fuselage for rigidity and low centre of mass. The tail skids provide some steering ability and give about 10 degrees resting angle of attack.

The takeoff run is generally problem free up until about 50m/s where it either tips sideways or rolls a wing into the ground. Trying to use the rudder to correct is ineffective, probably due to it lifting off around then. Roll controls have not much effect. I expect a no input liftoff about 55-65m/s.

I'm thinking it's to do with one wheel lifting and the drag from the other wheel spins it around but I can't work out how to avoid it.

It's possible to brute force it off the deck with thrust but then landing is impossible. Even a perfect landing touchdown results in the same result when brakes are applied or even if left to roll.

Any help would be greatly appreciated. This has been causing me problems for ages!

p.s. I experimented with a canard configuration aswell, although it was not as good to fly. It was able to roll safely at high speeds due to the front gear being held off the ground by the front lifting surfaces, and the centre of mass ahead of the rear gear. It was possible to brake to a stop but it was still very sensitive to misalignment and seemed to be more down to chance whether a wheel would dig in or not.

[Heagar]

What you described has a simple reason:

If the landing gear in front of your plane is at the same heigt or more than your landing gear in the rear, your plane will "dance" while accelerating.

To avoid it, your landing gear in the front must be slightly lower than the rear. A space (thickness of a wing) is enoungh for that to acomplish.

• You can for example use the Mk1 cockpit and mount a gear - witch is rotated 180 degrees - at the nose. Because the nose isn't at that level than the main body of your plane, that trick works.
  
• Or mount a wing beneath your plane on witch you place your rear landing gear.
  
• Or use a "small hardpoint" under your conventional mounted wing, on witch you place your landing gear. That has the same effect.
  
• You can even mount a "Tail Fin" under your wing (if that is mounted on top of the plane), witch you can use (with a small "control surface") as mount point for your landing gear and vertical stabilizer at the same time.
  

BTW: Your link refers to the main forum page. So i was unable to see your plane.

You can refer to a certain thread by opening it. Copy the text of the adress-bar in your browser (on the top of your screen) and use it for your link, like:

http://forum.kerbalspaceprogram.com/threads/71015-BSC-Aeris-4a-AND-THE-WINNER-IS?highlight=BSC

To refer to a certain post you open the thread and go to the page of your post. Search in the source-code of the page for a line like this:

<a name="post1020609" href="threads/71015-BSC-Aeris-4a-AND-THE-WINNER-IS?p=1020609&viewfull=1#post1020609" class="postcounter">#292</a><a id="postcount1020609" name="292"></a>

Then put the following lines together (replace in httx the x with p):

httx://forum.kerbalspaceprogram.com/

threads/71015-BSC-Aeris-4a-AND-THE-WINNER-IS?p=1020609&viewfull=1#post1020609

Then you should have the following (replace in httx the x with p):

httx://forum.kerbalspaceprogram.com/threads/71015-BSC-Aeris-4a-AND-THE-WINNER-IS?p=1020609&viewfull=1#post1020609

- a perfect link to your post in a certain thread.

In this case an example of a plane with under the wings mounted landing gear.

Edited September 7, 2014 by Heagar

[Daveroski]

Try moving your wings back a little to get the centre of lift further back or slightly angle the tail wings so that your centre of lift is lowered closer to the level of your centre of mass pushing the tail down.

In my opinion your aeroplane wants to lift more from the tail end and as you burn fuel the tendency will increase as centre of mass shifts back. While control at very low speeds will be good, as you increase speed, your aeroplane will want to flip.

[Pecan]

To do this I'm using FAR, spaceplane plus, and some firespitter landing gear. This lets me build some planes without having to go to space first for loads of science.

A much simpler way to avoid having to grind for science is called "sandbox". You might like to practice with stock parts before complicating everything with those mods.

[Geschosskopf]

In my experience, those big single "biplane wheels" in Firespitter are unusable. They never quite line up correctly when attached to the fuseflage, so the plane will always pull 1 way and then the other. I recommend not using them. Instead, use the small, double biplane wheels which, IIRC, are available on the same tech tree node.