— Sikorsky (@Sikorsky) June 20, 2017
The new Sikorsky Raider, testbed for some exciting new technology, is the epitome of a long development.
From the 1930’s, aircraft manufacturers have developed (hybrid) designs that attempted to answer the challenge of the need for a landing strip. The first practical helicopter design was the Focke-Wulf Fw 61, which flew in 1936. It looks nothing like the present archetypical idea of ‘helicopter’. This idea is heavily influenced by Sikorsky. It was their 1942 design of the R-4 that influenced the post-war development of the helicopter.
And now, Sikorsky’s new design, the S-97 Raider, for the American Army’s Future Vertical Lift (FVL) program as shown in the clips above, has one difference that quickly catches the eye: a second top rotor. Now, a second top rotor is not a new design in itself.
Existing helicopters already feature it, with the Russians having done extensive research into dual-rotor designs and fielding the, at the moment, fastest attack-helicopter using this technology, the Kazmov Ka-52, NATO codename ‘Hokum’.
It is the rotor on the back of the Sikorsky design that makes the difference. The Sikorsky Raider is the prototype for new development for the FVL-program. The FVL-program is the US Army program to design a series of replacements for all current helicopters it uses. This includes the OH-58 Kiowa, UH-60 Black Hawk, CH-47 Chinook, but also the AH-64 Apache. Like its predecessor the X2, the Raider isn’t a true helicopter design. It is actually a Gyrodyne.
In a Gyrodyne, there are other sources for propulsion than just the rotors, as in a ‘pure’ helicopter. But unlike in a Gyrocopter, the rotors are not just for generating lift. A Gyrodyne combines the vertical lift-off and landing of the helicopter with higher speed made possible by the extra engine and less stress on the rotor mount that negatively affects the maximum speed of helicopters.
This in itself is not new either. The first Gyrodyne flew in the late 1940’s. Airbus Helicopters, for example, broke the world speed record for rotary aircraft with a Gyrodyne-design.
There are other designs that try to solve the speed and range problem of helicopters, by taking a far more conventional design and just tilt the engines so vertical take-off and landing is possible: the tiltrotor design.
Each of these solutions have their strengths and weaknesses, but the interesting thing about the new Sikorsky design is the integration of multiple developments into one design. It is essentially a Gyrodyne with a dual rotor. It looks far more like our archetypical idea of a helicopter, while it is actually very different. Interestingly, the tiltrotor design is very like the first successful model helicopter, but with a twist. Both at least look good and competition of ideas never hurt anyone.