Have 3 buttons on the outer part of the handle. One each for the pinky, ring and middle fingers.
Why? Modifiers are very important on an advanced HOTAS and personally, I find a minimum of 3 are required which I know is more than most use. They of course don't have to be used as modifiers. But with three, you can easily map all 20 OSB buttons of a MFCD (those small in-cockpit screens with 5 buttons on each side) to a single hat switch.
The reason they should be placed next to each other on the outer part of the handle is because the pinky, ring and middle fingers are not as dexterous as the index finger or thumb making them a better choice for simple buttons and leaves the index finger and thumb for more complex controls like POV/Hat switches, thumb-sticks, rotaries, etc.
Instead of a split 2-lever throttle, have a single lever and a "balance" control.
I know this bucks the current trend of twin-lever throttles. But, here is why I don't think two is a good idea:
- The vast majority of the time the two levers are locked together. Usually only split if there is an engine failure.
- If you DO split their positions (perhaps because you're using the second lever for a control other than thrust) then the controls on each lever no longer line up! As your hand can't be in two positions at once, it makes it very awkward to reach all the controls.
- The "balance control" could be a simple knob or left-right slider. The output of the joystick would still show 2 independent axis, e.g. Slider1 (left) and Slider2 (right). It's just that their values would be calculated from the position of the physical throttle lever AND the position of the balance knob.
For example, if the balance control is in the middle, both Slider1 and Slider2 would get 100% of the throttle position. This is like having the throttles locked together. However, if the balance control was 1/2 to the left, then the Slider1 would get only 1/2 the value of the throttle position while Slider2 would get 100% of the throttle position. This would allow balancing throttle output just like you could with two physical levers, except done with a separate balance control.
Why bother? Well, because by making the throttle a single lever design, the handle can be one larger part rather than two smaller ones. This allows more room inside for the electronics. Possibly allowing for more ergonomic design, perhaps a bit like the F-16. It also solves the problem mentioned above where the controls would get offset if two levers are in different positions.
For specific index/thumb controls, I offer only general thoughts:
- Always use 4way+push hat switches (like on the MCG) rather than 2way. Always give as many options as possible and I'd suggest a minimum of 3 hats.
- Mini-joysticks are great but not always a good replacement for hat switches even if they can be emulated in software. They lack tactile feedback which is very important. I'd suggest only including a single one and using hat switches for the balance.
- Rotary controls aren't seen often anymore but would be a nice in addition.
tl:dr Don't be afraid to buck industry design trends and innovate! Allow many modifiers for those who need them (it won't hurt those who don't) and consider the possible benefits of a single lever + balance knob for engine output.
I realize that design is a very subjective topic but hope that even for those who prefer things otherwise, the reasoning provided will add to the discussion and be helpful, even if not adopted.
Thanks for the ear and good luck with the development!