I'm almost done with the needles. But the calculations to work out the rotation of the needle has me stumped. I've got it to almost match the texture scale, but not quite. Also, I was using the speed shown on the hud as a guide. But it turns out the speed on the hud was the wrong value. It showed world z velocity, so basically how fast an object is moving through the 3d world, unaffected by air, or any other physics. Once I changed that to use indicated airspeed, I got further.

I'll need a maths guru to help understand, or try and work out what the calculation is doing. I read this guide, and it helped a bit.