Basic plane design

[stormdot5]

Thought something like this might help people with some of the basic plane issues that repeatedly pop up. Tried to get as much as possible on one picture, rather than a long tutorial.

[Callmedave]

This is a good description. and will help me with my plane design (as im terrible at it!)

I thought the general rule was CoL was to be just behind CoM yours is behind and above, what affect does that have?

What would happen if it was below?

[RizzoTheRat]

Loads of info in one picture.  Nice.

 

Couple of points I'd add that are more of an issue for faster and heavier planes rather than early game:

• If you pitch the wing up slightly in relation to fuselage (front to back) you'll have a positive angle of attack on the wing when the fuselage is horizontal, this will generally reduce drag from the fuselage in flight
• Pitching the tailplane down slightly will mean it creates the downforce needed to counter the fact that the CoL is behind the CoM.  In the real world this makes your plane longitudinally stable, ie if a gust pitches you up you get more lift from the wing, but less downforce from the tail and so you pitch back down again.  As we don't have gusts in KSP this isn't much of an issue for us though. 

Re. CoM/CoL height, I believe a higher CoL should increase roll stability, as you roll the aircraft the CoM will end up to the side of the CoL, which will help pull it back level, but as you're also generating sideways lift I'm not certain how much effect this has, certainly having a CoT of a rocket above the CoM doesn't improve stability in this way.  A more effective way to achieve roll stability is with dihedral, ie the wing tips higher than the wing root, in this case as you roll the lower wing effectively has a greater lift area than the upper wing and therefore rolls you back up again.  Again with no gusts and plenty of reaction wheel torque this isn't much of an issue in KSP.

Edited April 27, 2016 by RizzoTheRat

[stormdot5]

12 hours ago, Callmedave said:

I thought the general rule was CoL was to be just behind CoM yours is behind and above, what affect does that have?

What would happen if it was below?

The Centre of Lift being above the Centre of Mass should result in a more stable aeroplane. Putting the CoL below the CoM can result in a more manoeuverable (or possibly unstable) plane.

CoL being behind the CoM is usually trimmed out once in flight to result in no net pitch moment.

[Callmedave]

Thanks for all the info.

I like that you have created this with not only stock parts, but early tech tree parts. Thumbs up for that!

 

Looking forward to putting this in to practice tonight after work!

[Callmedave]

Made a plane and had all the markers in roughly the right place, but the plane was very twitchy on takeoff, and would often skew of to the left or right and end up a fiery explosion.

Being in early career, I only had the tail fins and large swept wings available. Using the rotate tool I position the wings so they did not sweep back so much and viola! i now have a really good jet, great for the 'crew report below X at X' contracts! It flys nice and stays fairly level even with SAS off.

I discovered a nice tip using the 'deploy' feature of the tail fins to adjust the trim of the aircraft allowing it to fly perfectly horizontal. - I may make a video to show this.

 

Thanks again for the tips!