"Jim Vincent" wrote in message
...
I understand that that is the limiting factor to helicopter forward
speed.( and why 'Airwolf' could never have worked ) At around 400 kph the
forward going blade starts to overcome the amount of control input
available

I thought it was because the forward blade is approaching supersonic.

A one-off special version of the Westland Lynx has the record for
world's fastest conventional helicopter; it did 249 mph (401 kph),
albeit with special experimental rotor blades. Supersonic flow on the
advancing blade is a problem.

However a compound helicopter like the Lockheed Cheyenne AH-56
(stub wings and pusher prop in addition to main rotor blade)
or the XH-51A (pusher jet engine) could unload the main rotor and
do 250-300 mph.

I think the fictional Airwolf helicopter used pusher jets in
"supersonic" flight. IOW it was a compound helicopter, although
this wasn't clearly stated in the TV show. The Bell 222 it was modeled
on had stub wings for landing gear.

I don't know what the theoretical speed limit is for a compound
helicopter, but it's clearly faster than 400 kph.

But considering the difficulty of getting a winged plane to efficiently fly
supersonic, even if a supersonic compound helicopter was theoretically
possible, it's unlikely to be practical. There are better approaches, such
as tiltrotor up to about 350 mph (570 kph), and beyond that V/STOL
winged aircraft.

-- Joe D.