How to fly an airplane

[MetricKerbalist]

Hi KSP colleagues,

I doubt that I want to spend much time flying airplanes or spaceplanes with KSP.  I would like to try it at least once or a few times, however.

I am confused on how to even get started.  I am in the hangar, and I click launch.  For a rocket, after activating your engines and SAS, you hit the space bar and off you go.

But what do you do with planes, please?

Thank you.

Stanley

[MetricKerbalist]

Hi KSP colleagues,

OK.  I guess I figured it out.  Don't start in the VAB but in the SPH.

Well, let's see how well I do.

Stanley

[jimmymcgoochie]

1.  Apply the brakes to stop your plane rolling anywhere.
2. Start the engines, they’re usually the first stage.
3. Throttle up, let the jets spool up a bit.
4. Apply SAS to just hold attitude, then release the brakes when the engines have spooled up.
5. Wait a while until you reach a good speed- this varies very widely from plane to plane, but a typical jet should be able to fly at 100m/s- then carefully pull the nose up and the plane should rotate and begin to climb; don’t pull up too hard or you could smash the tail end of your plane off the runway and crash horribly.
6. And you’re flying!

Keeping a plane in the air is a balance of lift and gravity, but unlike in real life KSP’s wings generate lift solely by their angle relative to the air they’re moving through. You’ll probably want a few degrees of angle on your wings so that the front edge is slightly higher, this generates  ore lift at low speeds but will eventually produce more drag at very high speed. You need to keep going forwards to stay airborne, but turning a plane is relatively easy- bank the wings using roll controls and it’ll tend to turn on its own- and going up or down is even easier- just pitch up or down and keep an eye on your speed, too slow and you run out of lift, too fast and you could pull the wings off if you pitch up too sharply.

Landing can be tricky even for an experienced pilot, so the best way to land a small plane is to stick some parachutes on it and pop those open when you’re near where you want to land . But if you want to do it properly…

Vertical speed is what differentiates a landing from a crash, keep an eye on your vertical speed gauge beside the altimeter and set that altimeter to display altitude above ground level. The land around KSC is almost entirely flat so aim there rather than at the runway until you get the hang of landings; throttle the engines down, reduce your speed and altitude gradually and once you’re just above the ground kill your vertical speed with a ‘flare’- pull the nose up a bit and keep raising it as your speed drops to maintain altitude, then drop gently to the ground and apply the brakes carefully to avoid skidding, spinning, crashing, exploding…

[MetricKerbalist]

Hi @jimmymcgoochie,

Thank very much for the detailed explanation.

I will keep it handy for all my KSP plane-flying experiences.

Stanley

[herbal space program]

Some more advice on building a plane that will actually fly:

1) get to know the center-of-mass (CoM), center-of-lift (CoL), and center-of-thrust (CoT) indicators in the SPH.  A good plane will have the CoL indicator on or just behind the CoM indicator, both when the tanks are full and when they are empty.  Achieving this balance is not trivial, and I highly recommend using wet wings  rather than just tanks to help you with that.  Trying to mount at least some of your engines further forward along the sides rather than having them all in the back helps as well.  If your CoL is too far behind your CoM, your plane will keep trying to nose down. if it is in front of your CoM, your plane will flip over and try to fly backwards the second you go off prograde.

2) Don't forget to put control surfaces! You'll need both horizontal stabilizers and a tail fin of some kind near the back, and sometimes a canard on the front can be quite helpful as well.  Also, surfaces that are meant to control your pitch should be either well forward or well aft of your CoM. 

3) Put most of the weight on the rear wheels, but don't have your tail sticking out too far. Takeoff and landing are much easier if your rear wheels are relatively widely spaced and just a little ways behind your CoM, while your nose wheel is as far out in front of your CoM as you can put it. This also puts quite a bit more weight on your rear wheels, so they should often be one notch beefier than the nose wheel.  The front and rear wheels should also be mounted so that your plane is pitched slightly up on the runway, so that your wings generate lift as soon as you get rolling. As was mentioned before, tilting the wings slightly up in the SPH is often a good idea as well, as it allows you to generate lift while your fuselage is pointed directly prograde, which minimizes drag in flight. Having said all that, make sure your tail section doesn't protrude so far behind the rear wheels that it will hit the runway when you pitch up for takeoff!

4) Familiarize yourself with "absolute" vs. "local" mode when using the "rotate" tool in the SPH. You should  make sure all your wheels and  control surfaces are absolutely horizontal/vertical with respect to your fuselage before taking off, or else you could see some bad behavior.

5) Consider turning off the steering on some or all of your wheels, at least for takeoff/landing. I generally find that they respond too aggressively to control inputs in these situations, greatly increasing the probability of disaster.

Happy flying!

 

 

[Blaarkies]

If your plane behaves unruly in the sky, I would highly recommend reading this post

 

[herbal space program]

6 minutes ago, Blaarkies said:

If your plane behaves unruly in the sky, I would highly recommend reading this post

 

This is a very nicely written tutorial, just keep in mind that it is so old that it says stuff about the  KSP aero model that is no longer true.

[herbal space program]

1 hour ago, jimmymcgoochie said:

1. You’ll probably want a few degrees of angle on your wings so that the front edge is slightly higher, this generates  ore lift at low speeds but will eventually produce more drag at very high speed.

If you do it to the right degree, it actually produces less drag at high speeds, because it lets you keep your fuselage pointed directly prograde while your wings still have some angle of attack. Adding more rather than less wing area can also somewhat counterintuitively reduce drag at high speeds/altitudes, because it lets you keep your fuselage pointed more prograde up where the air is really thin.

Edited June 23, 2021 by herbal space program