I wouldn’t want to be the pilot.
There’s pics of the model and specs of the proposed design. Even today, I don’t really think such a chopper would be feasible.
The rotor-tip lifting system thing - jet engines attached to the end of the blades to make them revolve faster - sounds pretty effing cool, though.
The Fairey Rotodyne had something like that. Colossally noisy.
Which makes me doubt he aero-cred of that author. He mentions a tail rotor on the Hiller, but the Rotodyne (with the main rotor also powered by tip jets) had no need of a tail rotor.
The seventh engine was probably for forward thrust, not anti-torque.
It may not need a tail rotor to counter act the high torque of conventional helicopters, but it would need a tail rotor for yaw control.
The Rotodyne controlled yaw with the engines mounted on the wingtips. The propellor pitch was independantly controlled with rudder pedals.
I’m still gobsmacked by the idea of the rotors approaching the speed of sound. :eek:
Well, you have to think about the size of the rotor. If each blade is 450’ long, the tips would be traveling at 800 MPH at just 25 RPM.
I wonder what the rotor speed would be to hover.
I think each rotor blade would be about half that long, since the diameter was about 400 feet.
I understand the combination of forces that result in that… I’m just trying to imagine a helo where the rotors are approaching a sonic boom… And the material science to build the silly things.
The more I think about it the more it boggles my mind. Not only would those rotors have to withstand the stresses of near supersonic speeds, but also support the weight of two jet engines, plus fuel delivery systems.
In the air, the inner portion of each blade would have to support one-third of the helicopter and Saturn V first stage; so I wouldn’t be real worried about a couple of jet engines.
From the OP
The diameter was greater than 300yds -> 900’
Shh… don’t remind me of that. 
But further down in the article, it says "It would be a monster. The rotor diameter would be over 120 meters (400 feet). " Maybe someone got their feet mixed with their yards.
“The rotors would not have to turn very fast by helicopter standards, only about once per second. But even that would result in the advancing rotor tip approaching the speed of sound.” It’s not clear if that is hover speed or transport speed.
FWIW, a football field is only 100 yards long, not 300. I think that’s the source of the confusion.
Yup. The diameter would be over 300’, not 900’. But what a fucking spectacle that beast would be, huh? I bet it’d sound like the wrath of God.
Let’s do it! 
Ya know, I double checked my numbers after I was called on it too. I watch football. I know that the middle of the field is the 50 yd line and that there’s 10 yds of endzone at each end. So yeah - 120 yds = 360’
So, 6.4 MPH for every RPM - which is about 110RPM for the tips to approach mach one in a hover.
But, if the heli wanted to be able to fly forward, the rotor speed would have to be less so the advancing tip wouldn’t break the sound barrier.
Tuckerfan: “Only two V-12 prototypes were built, yet despite its amazing size and lifting power, the design was considered a failure by its manufacturer and Soviet authorities.” – sounds like something Bruce McCall would draw. Ever seen his art work (Natl Lampoon, New Yorker)? I think he drew something like this, called the “Zud”. A crease in the blueprints caused a crease in the fuselage because no line manager wanted to admit to a mistake.