[gurps] Autogyro performance

[Onno Meyer]

Brandon replied to me:
> > > Minimum speed for 30 mph, take-off run of 30
> > yards,
> > 
> > Assuming constant acceleration, the autogyro would
> > need
> > an acceleration of roughly 7 mph/s for that takeoff
> > run.
> > Not surprisingly, Vehicles agrees.
> 
> So far my designs have fallen a bit short of this
> (although so far only one is an historical design).

The C30A had a 104 kW engine and a Lwt of 0.9 tons, 
so unrounded gAccel should be 8.5.

> One ability of some autogyros to briefly power the
> rotor to get it to full rotation speed, then disengage
>  the power and apply it all to the prop needs to be
> accounted for. This can radically shorten the take-off
> tun to single-digit yards. And no, this gearing isn't
> nearly as heavy or complicated as a helicopter
> transmission.

Define a new helicopter drivetrain type. Special 
effects: It provides static lift, but only for 
purposes of the stall speed calculation, and it 
does so for x seconds after power is cut.

> > That could also help to explain the low stall speed
> > of 
> > modern designs. They're little toys, with a better 
> > area to weight ratio.
> 
> I'm not sure I could call them toys -- they are just
> very light aircraft.  One YouTube video was a
> promotional film showing the advantages of a light
> autogyro over a light helicopter, including one being
> used by police for search and rescue.

Talking averages here.