[gurps] Autogyro performance

[Onno Meyer]

> I've known for quote some time that the formulas in
> VE2 didn't work for autogyros. They results in stall
> and top speeds too high and takeoff and landing runs
> too low. Anyone found a solution?
> 
> Brandon

The formula for the takeoff and landing runs is based 
on stall speed and acceleration/deceleration. I would 
not change that formula, so that leaves three rules:

* Deceleration is an extremely simple formula, but it 
  tends to be much higher than acceleration, so it is 
  a secondary question.

* I have the (unverified) gut feeling that gAccel for 
  light prop aircraft is way too high and hence their 
  takeoff runs are too low. So boosting gAccel would 
  be a bad idea.

* That leaves the stall speed formula. Using the VXii
  rules, you could change the lift area multiplier 
  for rotors without side effects for other aircraft
  (since helicopters have stall speed 0 anyway). 

What data do you have on autogyro stall speed?