Story ID: 462
S-97 Raider Highlights Sikorsky Advances
By: David Donald
Caption: Sikorsky’s 210-knot compound helicopter appears in Paris
Word Count: 516
Sikorsky’s S-97 Raider compound helicopter is making its international debut this week at the Paris Air Show. The type embodies the company’s X2 technology, which was first tested on a technology demonstrator of the same name that first flew in 2008. The S-97 formed the basis for the company’s S-102 Raider X, which was proposed for the U.S. Army’s Future Armed Reconnaissance Aircraft (FARA) requirement.
Although the FARA program was canceled by the Army in 2024, with Sikorsky having built a single unflown prototype, the two S-97s have continued to be used as development tools. These helicopters fly on average once a week to trial new technologies for the continued advancement of the X2 concept and for applications to other Sikorsky types such as the S-70 Hawk family.
Sikorsky’s X2-based proposal for the Future Long Range Assault Aircraft (FLRAA) Black Hawk replacement, the SB-1 Defiant developed in partnership with Boeing, lost out to Bell’s MV-75 tiltrotor design.
At the heart of X2 technology is a short-diameter, variable-speed coaxial main rotor layout employing highly rigid blades that offset the risk of retreating blade stall. A tail-mounted pusher propeller provides most of the thrust in forward flight, giving the S-97 a top speed of around 210 knots, while other X2 family members have reached 250 knots. Flight control is by fly-by-wire, and the propeller is variable pitch, including reverse, and can be used for deceleration.
For the pilot, this feature is very useful, as the helicopter can be brought to hover or land with no need to raise the nose, which greatly reduces the pilot's forward hemisphere visibility at a critical stage of flight. Other flight characteristic advantages provided by the propeller are the ability to make tight turns and accelerate out of them, making the helicopter less vulnerable over the battlefield. The S-97 can fly sideways at up to 50 knots.
Despite the loss of the FLRAA competition and the cancellation of FARA, Sikorsky views X2 technology as having a key part to play in future rotary-wing projects. A major opportunity is NATO’s Next Generation Rotorcraft Capability, for which Lockheed Martin/Sikorsky was awarded a concept study in July 2024. That is due to be delivered in the fourth quarter, along with those from Airbus and Leonardo.
Rotor Blown Wing is another technology that Sikorsky is actively developing and testing as part of a DARPA program. The first 115-pound demonstrator began flight trials last year, paving the way for a 330-pound vehicle to fly next year. The rotor-blown-wing concept is for a tail-sitting UAV that takes off and lands vertically on the thrust from wing-mounted propellers, before transitioning to wing-borne flight. The small-scale demonstrator reached 86 knots during initial trials.
Harnessing the advantages of both fixed- and rotary-wing air vehicles, but without the need for complex mechanisms such as tilting wings or rotors, frees the vehicle from runway independence and facilitates maritime operations. However, the rotor-blown-wing concept does require new control laws, as well as advanced autonomous systems.