Another little something different
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Another little something different
I could swear I posted this already, oh well, anyway...
I'm pretty sure this one's already out there, but...
Dual rotors - intermesh, interleave or side-by-side. Rigid rotor system(s). Drive the rotors as usual, cross-connected via a gearbox, sprag clutch, engine. Also driven by the engine from a second output shaft , through a engaging clutch and constantly variable transmission with lockup, is a ducted fan for forward thrust.
The aircraft flies like a helicopter, with all power going to the rotor system, allowing hovering, maneuvering and entry into cruise. When going to cruise, the ducted fan is engaged and takes the job of providing forward thrust. As more and more power is shifted to the fan, the rotors go into autorotation and all forward thrust comes from the fan.
Pitch stability, altitude control, and rotor RPM control is accomplished by combining cyclic/collective feathering and a trimmable horizontal stabilizer. Bank is controlled via differential rotor pitch and trimmed with vertical stabilizer control. Alternately (or in conjunction), the fan thrust could be vectored.
Using advanced rotor controls, the rotor could be slowed and the retreating blades could be "reverse" feathered to eliminate retreating blade stall.
The fan thrust could also be used to augment maneuverability (and the longitudinal CG envelope) in the hover.
OK there it is.
I'm pretty sure this one's already out there, but...
Dual rotors - intermesh, interleave or side-by-side. Rigid rotor system(s). Drive the rotors as usual, cross-connected via a gearbox, sprag clutch, engine. Also driven by the engine from a second output shaft , through a engaging clutch and constantly variable transmission with lockup, is a ducted fan for forward thrust.
The aircraft flies like a helicopter, with all power going to the rotor system, allowing hovering, maneuvering and entry into cruise. When going to cruise, the ducted fan is engaged and takes the job of providing forward thrust. As more and more power is shifted to the fan, the rotors go into autorotation and all forward thrust comes from the fan.
Pitch stability, altitude control, and rotor RPM control is accomplished by combining cyclic/collective feathering and a trimmable horizontal stabilizer. Bank is controlled via differential rotor pitch and trimmed with vertical stabilizer control. Alternately (or in conjunction), the fan thrust could be vectored.
Using advanced rotor controls, the rotor could be slowed and the retreating blades could be "reverse" feathered to eliminate retreating blade stall.
The fan thrust could also be used to augment maneuverability (and the longitudinal CG envelope) in the hover.
OK there it is.
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It IS "already out there"; ~ in the minds of forward thinking rotor dynamists who are not constrained by the mindsets of the past.
There are many technical reasons why the single rotor should never have become the predominant one. However, for a different perspective, here are a couple of selections from the book by William Hunt, Igor's designer and project leader for the XR-4 and XR-5.
"By the mid 1930's Europe was more advanced in helicopter development than the USA. However, the European models that enjoyed initial success were all multi-rotor types: ....... Not one successful single-main-rotor helicopter existed anywhere. It was just the type of challenge that Igor Sikorsky needed to reactivate his thoughts regarding aircraft that did not need running takeoffs and landings."
"Another of Igor's talents was his ability to 'sell' his ideas to others." Apostrophe by William Hunt.
The single rotor became predominant because it was a challange to do something different, then sell like hell????
There are many technical reasons why the single rotor should never have become the predominant one. However, for a different perspective, here are a couple of selections from the book by William Hunt, Igor's designer and project leader for the XR-4 and XR-5.
"By the mid 1930's Europe was more advanced in helicopter development than the USA. However, the European models that enjoyed initial success were all multi-rotor types: ....... Not one successful single-main-rotor helicopter existed anywhere. It was just the type of challenge that Igor Sikorsky needed to reactivate his thoughts regarding aircraft that did not need running takeoffs and landings."
"Another of Igor's talents was his ability to 'sell' his ideas to others." Apostrophe by William Hunt.
The single rotor became predominant because it was a challange to do something different, then sell like hell????
Last edited by Dave_Jackson; 11th Sep 2006 at 20:37. Reason: Changed text format
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Re: Another little something different
Originally Posted by NickLappos
He also described the XH-59A ABC, which flew 23 years ago!
OK so looking at the "X-Wing" (not the XH-59) - it seems to have two smaller turbines driving the rotor and two turbofans for thrust. So we put "X" rotors out on the end of winglets and a big ol' turbofan (or two) inboard, like a Harrier. We steal as much power as we can away from the fan to run the rotors, duct the fan output down and laterally for hovering and slow flight, then send it aft as we transfer full power to the fan. Hey, if nothing else, it's way cooler than the V22 and better in vertical flight.
OK, well, I'll keep my day job...
