Yaw � how to use it?

[Geschosskopf]

I'm not saying you can't do it with a keyboard, but the keyboard is so overly sensitive (On or Off, nothing in between) compared to an analog control that you can just barely nudge to get a nice smooth turn. Even tapping I'd imagine it's a bit shaky. Does that matter? Well it does to me, but I may not be the best one to ask

I find the keyboard perfectly responsive and totally adequate for fine control. See, it takes some amount of time for the control surface to move to its full deflection position. If you don't want full deflection for what you're doing, you hold the key down only long enough to get the control surface to the angle you want, then release. The control surface then starts moving back to neutral at the same speed it deflected. So very shortly after release, you tap the key again. This gets it moving back towards deflection, then it starts back again, and by repeatedly tapping you can keep the surface at any arbitrary deflection you need.

[DancesWithSquirrels]

Comments from a not terribly expert pilot (um, me):

The best turns are 'coordinated' turns, where the nose tracks the path of the plane through the air. The utter vast majority of aircraft won't do this under roll/pitch maneuvers, either sliding out (more common, nose pointing less than the turn angle) or into (tail swinging out) of the path. This is less efficient, and if you're not paying attention can lead into nasty bank angles or stalls. One major reason for this adverse yaw is that when you, for example, bank left, the right wing is lifted by the aileron producing more lift and induced drag, pulling the nose out.

The most common use of the rudder is to coordinate the yaw with the pitch/roll turn so that you point along your trajectory. You can force a turn with the rudder alone (I used to do that in QuickSilvers), but it's really sloppy.

Note that there are some interesting variations on this: Uneven aileron deflection up/down (inner aileron rising and dragging more than outer drops) can greatly reduce adverse yaw. The Ercoupe (2-axis controls) interlinks ailerons and rudders to avoid adverse yaw, and IIRC the Piper Colt has bungee interconnects so that if you don't touch the pedals they will track ailerons in a similar manner. High dihedral (upwards angled wings) increase stability and help by somewhat coupling roll inputs and yaw, although I don't know if that's going to be properly simulated in KSP. There are small and slow(ish) two-axis planes with rudders but no ailerons, such as the old ultralight Weedhopper or the Flying Flea, where the aerodynamics or just the difference in speed between inner and outer wing induce a bank - those generally don't fly in a very coordinated fashion, but they don't (they can't) diverge enough to be a risk.

This is probably far more than anyone actually wanted to hear, but it's an interesting subject for me - uncoordinated flight where the rudder and ailerons are moved out of unison are a significant cause of low-speed stall/spin accidents and crashes; I've always considered 2-axis control a significant safety feature.

---

General rule of thumb - It's nice to fly coordinated, but you don't need it most of the time. If it's causing problems, just put a fixed stabilizer on the plane. You can wreck a plane with far less extreme maneuvers by accidentally crossing controls than you can with just 2-axis control surfaces.

---

Edit: SAS can really be a pain for maneuvering a plane - I bank to turn with Q/E, and the reaction wheels in the pod try to maintain heading instead. Adding yaw with A/D is needed, and that's not smooth. I try to get the trim tuned far from the ground to fly (mostly) hands off and disable SAS long before landing.

Edited August 14, 2015 by DancesWithSquirrels
Added SAS bit

[FlyingPete]

IRL, yaw keeps the G-indicator in the middle. Basically, when you bank turn, you don't need to bank 90 (or close to) degrees. Theoretically, one might think so (and yes if flying a fighter jet or so), but because of earths gravity and whatnot you dont bank that much - hence yaw to keep you turning nice.

You'll notice this whenever you're on an airliner. Even though you're rolled by up to about 30 degrees in a turn, your sense of 'down' is still directly towards the floor. Too little rudder input, and the plane slips into the turn ('down' shifts towards the lower wing), too much rudder, and you skid out of the turn. Neither are very efficient.

One thing that's quite useful is if you're going for a runway landing and are off-target, you can keep the nose pointed at 90 degrees (or 270) with the rudder input, while rolling the plane left or right to slip sideways in order to line up.

[LN400]

Yaw, or rudder would also be the primary control for lining up with the runway for landing. You don't want to bank a lot near stall speed.

[cantab]

For what it's worth, most of my planes have pretty much "self-coordinated". Maybe not perfectly, but well enough that I'm happy to turn using bank and add a little pitch to keep the nose up and not touch the rudder at all.