How to make a stable plane

[SapphireDragon]

Hi I was wondering if yall could provide me with some help as to how to make a plane that is easy to fly and is stable, ive messed around with planes once or twice, and have made some smaller examples to get to understand how planes function, but they have been plagued with unusable handling

[superosh]

https://www.youtube.com/watch?v=K0fQ-xiDtUw&list=PL4BURbFo2Ihp0u_5hD7k6K0EmjpAkVt4F&index=6

[Bacnsnaxx]

Try adding a togglable gyroscope. Connect player inputs to the gyroscope (roll for banking/ailerons, pitch for elevators, and yaw for horizontal stabilizer) and the stabilized outputs to the control surfaces.

Connect a button or toggle key to turn on/off the gyro, you should be able to turn it on for enhanced stability at the cost of freedom of movement.

I recommend downloading a small, basic trainer plane, and practice flying if your piloting skills are lacking or study the design if your building skills are lacking. Planes require a lot of fine tuning to work well, so try to find what's wrong and change the plane or the controls.

For example, if the pitch stability is terrible and the plane keeps flipping out, make it longer, mess with wing or weight placement, or adjust the sensitivity of the pitch controls.

[superosh]

It's much better to make the plane natural stable as best as you can, before using the gyro.
The gyro(if still neded) should be just a small helper to make flying more comfortable.
Building a unstable plane, and let the gyro try to sort this out is a bad design.

If pitch is going crazy, then the engine is not aliigned(enough) to the center of gravity.

[AdmiralTigerclaw]

Originally posted by SapphireWolf:

Hi I was wondering if yall could provide me with some help as to how to make a plane that is easy to fly and is stable, ive messed around with planes once or twice, and have made some smaller examples to get to understand how planes function, but they have been plagued with unusable handling

In general, aircraft can be best described as a set of levers working around one of two fulcrums.

The first, and foremost is Center of Mass (CoM). Everything your aircraft does requires knowing this. There is a button on the building screen to turn it own and view it as a purple box.

The second is your aft landing gear. Please see the following KSP image I made years ago:

https://imgur.com/ELgSaxI


Additionally, when building an aircraft, you must also consider a behavior known as 'shuttlecocking'. If you've played badminton, that's the birdie's behavior when you hit it. The heavy mass of the base travels in the direction its struck, and then the cone-like area, the feathering, catches drag from the air around it, dragging it backwards. This forces the birdie to 'point' in the direction of travel, lead by the center-mass.

In an aircraft, the CoM is like the base of the birdue, and the center of lift (CoL, not shown in Stormworks) acts like the feathering. As a rule, your CoM MUST be kept in front of your CoL, or your aicraft will become more and more prone to departures from control. If the CoL is fully in front of your CoM, your aircraft will in fact have a strong desire to flip around backwards.


After all this, the next important factor is your line of thrust. For the most stable experience, your line of thrust must pass through your CoM. Diversions to the side result in thrust-induced leverage, or torque. And the further offset, the more extreme it becomes. In normal aircraft, things such as your tail section can counter-act your line of thrust's torque. You also get more leeway from propulsion that pulls rather than pushes. Propeller planes with engines on the front tend to be more stable since the leverage of the line of thrust is all the way out on the leading end of the aircraft, like if you were trying to crank something but pulled it all the way to one side.

The main takeaway is this: Don't offset your engines too far above, or below your CoM, or you'll experience nasty pitch behaviors just by throttling.

This KSP visualization shows you what having the engines slightly high does to torque.

https://imgur.com/PCXgA5d


As you can see, the program predicts a pitch down behavior from the engines looking straight forward, but ABOVE the CoM. Think of it as if you drew a line up from the CoM, and out from the engine, and where they intersect, is where the lever is being pushed.



Helicopters and VTOLs are also governed by CoM, but I won't confuse you with how those work.