[gurps] Autogyro performance

[Onno Meyer]

> Minimum speed for 30 mph, take-off run of 30 yards,

v = speed
a = accel
t = time
d = distance

So we have roughly v = 13 m/s after d = 27 m.

v = a*t <=> v/a = t
d = 0.5 a t^2 <=> d = 0.5 a (v/a)^2 <=> d = 0.5 v^2/a <=> a = 0.5 v^2/d
a = 0.5 * 169 m^2/s^2 / (27 m) = 3.12 m/s^2

Assuming constant acceleration, the autogyro would need
an acceleration of roughly 7 mph/s for that takeoff run.
Not surprisingly, Vehicles agrees.

> landing roll of 3 yards.

decel 70, or roughly 3.5 Gs. That is way beyond anything
Vehicles would allow, unless it was below 30 mph prior 
to the landing.

To get the stall speed (i.e. minimum level flight speed) 
down to 30, what about larger rotor area in proportion 
to the body? Take a flimsy structure and cloth armor, 
and the weight shouldn't be prohibitive. Drag goes up, 
but then autogyros were not exactly noted for speed. 

The C30 would need a rotor area of 400 sf, which is a 
notional volume around 100 cf, but then volumes in VE
were always a little artificial - streamlining should
increase the area for a given volume, not the volume
itself ...

That could also help to explain the low stall speed of 
modern designs. They're little toys, with a better 
area to weight ratio.