During the X2 Technology Demonstration, the S-97 Raider performed a flight display to show the capabilities the X2 technology.
On Feb. 12, 2025, during the second day of the X2 Technology Demonstration event at the Sikorsky Development Flight Center, the S-97 Raider flew a display to show its capabilities, which differentiate it from traditional helicopters. As mentioned in the first part of this report, The Aviationist was among the outlets that were invited to attend the event and see the S-97 demonstrator in action.
The flight display was preceded the day before by a simulator session and a briefing with Sikorsky’s experimental pilot Bill Fell, who also flown the S-97 in the demonstration. The briefing allowed a better understanding of the maneuvers demonstrated in the simulator and the ones of the actual flight display.
A great emphasis was put on the acoustic signature and the pusher propeller. The sound is already much lower than a traditional helicopter, as we had the chance to experience the day before when an S-92 departed from the facility for a test flight.
To give a better idea, the helicopter was on the ramp while we were walking around the static S-97 in the hangar, about 50 meters away, and it was difficult to hold a conversation. While the S-97 was hovering in front of the attendees at the same distance, the problem was not as prominent, and we could easily continue to conversate and hear Sikorsky’s officials describing the demonstration.
During the various maneuvers, the sound of the S-97 was audible only once the aircraft started coming into sight, giving only a few seconds of heads up to look for it in the sky. For an instance, many attendees noticed the S-97 sneaking up at high speed from behind the audience only when it was directly overhead.
The pusher propeller can allow multiple different uses, in addition to simply providing higher speed. As it was demonstrated throughout the demo (and explained here in the next paragraphs), the propeller can be used to change the attitude of the helicopter during the hover, to push it at higher speed or to slow it down, acting as a brake.
A notable example worth mentioning would be the ridge crossing during a terrain following flight, or nap-of-the-earth as it is called. Usually, while climbing over a ridge to cross it, the pilots have to carefully manage their kinetic energy to avoid ballooning up high above the ridge and exposing themselves to threats.
By using the pusher propeller with a negative pitch while closing in on the ridge, the helicopter can dissipate the excess energy and make sure to stay as close as possible to the ridgeline. Also, while descending on the other side, the prop can be used to slow down and keep a constant speed, which allows to stay as much as possible close to the grounds. The one just described was one of the maneuvers we tested in the simulator.
Let’s now describe the main maneuvers demonstrated during the flight display.
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Precise Low-Speed Handling
The S-97 has demonstrated during testing the ability to fly at 50 knots in sideward flight, while during the demo the aircraft performed the maneuver between 30 and 40 kts. This type of maneuver can also be performed by traditional helicopters, but there is a difference.
Instead of relying on tail rotor for yaw control, the Raider utilizes the torque differential between its coaxial main rotors to achieve the same effect. In conventional helicopters, tail rotor effectiveness varies based on flight direction and wind conditions, leading to different handling characteristics. In contrast, the X2 technology maintains consistent yaw control regardless of direction, improving maneuverability in low-speed operations.
Level-Body Acceleration
The pusher propeller enables acceleration in level flight. Initially, when starting to move forward, the aircraft tilts its rotors forward to increase airspeed, using the main rotors for initial thrust before engaging the pusher propeller. This way the S-97 can get “a bigger bite of the air” until airflow is established through the propeller, allowing to add power and bring the nose up, so that the aircraft transitions smoothly to forward flight, maintaining a level attitude.
“It’s just using the machine in the best possible way,” said Fell. “When you’re in a hover, you’re using this big rotor to grab a big bite of the air and accelerate quickly. It’s a good feeling in the aircraft because you can start asking for the prop and you feel that inflow build, almost like a turbo kicking in, and you can start flying more like an airplane.”
The X2 is designed with a clutch-controlled pusher prop, allowing the pilot to engage or disengage forward or reverse thrust as needed. The system allows the pilot to apply forward or reverse thrust throughout the flight envelope.
This way, the aircraft can accelerate from a hover like a conventional helicopter, engage the pusher prop at 100 knots, and continue forward flight efficiently. It’s up to the crew to decide how they want to operate the aircraft, without having restrictions on the usage of the pusher propeller.
During flight testing, an issue with the pusher prop required its temporary removal. The prop was replaced by a ballast and the S-97 continued testing, reaching 150 knots without problems. This further demonstrates how the presence of the prop does not restrict the operation of the aircraft, except for the maximum speed achievable.
High Turn Rate Maneuverability
To achieve tight turns, the S-97 can add reverse thrust on the pusher prop to decelerate while maximizing load factor, close to 3G, with a bank angle of 60°. As the aircraft exits the turn, forward thrust is reintroduced to regain speed efficiently. This method allows to reduce the turn radius as much as possible while still exiting the turn at high speed.
Such feature would be particularly useful for evasive maneuvers when a popup threat requires a quick change of direction even when flying at higher speeds. In fact, usually, the higher the speed, the higher the turn radius.
200 kts High-Speed Cruise Flight
The X2 can maintain a sustained cruise speed of 200 knots at low altitude while retaining responsive maneuverability. The aircraft’s roll control and agility allow it to navigate obstacles easily.
“I’ve flown the aircraft at treetop level at 200 kts and maneuvered around and below the trees. The X2 technology has an amazing roll response and maneuverability to be able to react to any obstacles coming at you quickly” said Fell. “I feel that if you get to like 250 kts you’d better be 50 ft or 100 ft off the ground because you need a little bit more clearance from the terrain.”
Speed performance depends on engine power, payload, and propeller configuration. When reaching 100 knots in the S-97, as this Author has experienced himself in the simulator, the collective is programmed to go down, resulting in 90% of the power being directed to the pusher propeller, with the remaining 10% is allocated to the main rotors.
This might seem a bit counterintuitive for pilots, explained Fell, as in traditional helicopter the collective stays up at higher speed. In the S-97, with the Advancing Blade Concept, the helicopter can reduce rotor pitch while flying at high speed and rely primarily on the pusher prop for thrust.
Dive on Target
A maneuver simulated during the demonstration was a target engagement. For that, the S-97 assumed a 20–30° nose-down attitude throughout the dive while maintaining a constant speed by using the pusher prop as a brake, adding negative pitch.
This is particularly beneficial for attack missions utilizing unguided weapons, as a steeper dive reduces dispersion and increases accuracy, said Fell. Also, the ability to control the descent rate without accelerating allows not only for improved targeting precision, but also for more time on target before having to break off the dive.
Level-Body Deceleration
The X2’s ability to decelerate while maintaining a level attitude can enhance operational safety. When landing in traditional helicopters, the deceleration requires raising the nose, which can reduce visibility in one of the most critical phases of flight, particularly when approaching an unfamiliar landing zone at night or with low visibility. The X2 allows pilots to slow down while maintaining an unobstructed view of the landing area, improving situational awareness and reducing risk, whether in military or civilian applications.
“You’re coming in a landing zone in the middle of the night, you may be browning out, you have not been there before, if you’re lucky you got some satellite imagery of that place, there could be wires that you couldn’t see, and it would be nice to keep looking at that place while you’re coming in to land and insert the assault force,” said Fell providing an example. “In a traditional helicopter you have to raise the nose and, if you’re lucky, you can still see something through the chin bubble or you’re able to peek over the dash a little bit, while with the X2 you can slow down and look out the entire time without raising the nose.”
Such a feature can greatly improve the safety of flight regardless of military or civil aviation. Another great example provided by Fell was a MEDEVAC (Medical Evacuation) helicopter having to land on a highway to rescue the victims of a car crash. Not only the highway could be considered as a confined space, and it could also include many obstacles like light poles, wires, signs, so having a good visibility during the landing is fundamental.
Nose-Down Hover
The X2 technology allows to hover in either a nose-up or nose-down attitude by adjusting the pusher propeller’s thrust. This feature, for an instance, can enhance reconnaissance and observation missions by providing better visibility of a target area. Currently, these adjustments require manual control through cyclic, collective, and propeller inputs, but future developments could introduce an automated function to simplify operation for the pilot and reduce the workload.
Hover with propeller disengaged
By disengaging the pusher prop, the -97 significantly reduces its acoustic signature. In fact, similar to how a tail rotor contributes to noise in conventional helicopters, the pusher prop is a primary source of sound in the X2 technology. When declutched, the propeller rotates at low speed, reducing the noise in what Sikorsky calls the “Whisper Mode”. Also, the coaxial main rotors operate at reduced RPM compared to a single main rotor, further decreasing noise levels.
This reduction in acoustic signature is advantageous not only in military operations, where stealth is a priority, but also in civilian applications, particularly in heavily populated urban environments, where lower noise emissions can improve operational viability.
