Glide speed generally provides sufficient windmill RPM on the engine(s) to
provide sufficient hydraulic power so that the controls (they don't have to
be fly-by-wire, any irreversible hyd flight control system is effected) have
sufficient pressure and volume to operate normally with moderate control
inputs.

R / John

"Charles Talleyrand" wrote in message
oups.com...
Suppose a smaller airplane with it's fly-by-wire controls goes runs out
of fuel. All the engines quit. On a larger jet a ram air turbine
would drop into the airstream and power the controls. How does it work
on smaller planes like the Dassault Falcon or the F-16?

Alternatively, I've always wondered if one could not keep a special
reserve tank for the APU. When the engines quit, the APU
automatically starts to power the controls. Would such a system be
safe and would it be certifiable? Would it weigh less than the
existing system?

-Charles Talleyrand