The assembly of Sikorsky’s Raider X competitive prototype for the Army’s Future Attack Reconnaissance Aircraft (FARA) program is now 90 percent complete. The compound coaxial helicopter with fly-by-wire flight controls is a semi-finalist in the FARA competition. It is 20 percent larger than the 11,000-pound S-97 proof of concept vehicle Sikorsky first flew in 2015. Sikorsky recently displayed the Raider X during a media briefing at its West Palm Beach, Florida test center.
The company said the use of additive manufacturing, also known as 3D printing, digital tools, and other advanced processes has reduced lead-time for aircraft components by more than 50 percent. The maturation of this technology across Sikorsky parent Lockheed Martin and its supplier base for both metal and composite materials is producing schedule, cost, and weight savings across systems.
However, flight testing of both the Raider X and its competitor, the Bell 360 Invictus, has been delayed until October 2023 (the start of Fiscal Year 2024) at the earliest due to delays with the GE T901 improved turbine engine selected by the Army. GE attributed the delay to Covid-induced supply chain disruptions.
The T901 is designed to be used in FARA aircraft as well as being retrofittable into the existing Black Hawk and Apache fleets. GE claims that it delivers 50 percent more power, 25 percent better fuel economy, and 20 percent greater engine life than the T700 engine it will replace. The design combines the single spool architecture of its current T700 with ceramic composites found on GE’s new generation commercial jet engine models, including the CFM LEAP, in a way that lowers weight and increases performance and efficiency. The engine is being provided to Sikorsky and Bell directly by the Army.
While Bell is fielding a conventional-looking design reminiscent of the RAH-66 Comanche program of the 1990s, Sikorsky is offering one based on its X2 technology that features a pair of rigid, four-bladed contrarotating main rotors assisted by an aft-mounted thruster.
Key members of the Raider X team maintain that the Sikorsky design provides superior stealth, speed, maneuverability, survivability, flexibility, and potential for mission growth over a conventional helicopter. In addition to the 20mm nose cannon, modular weapons launchers mounted behind the side-by-side-sitting pilots can be removed, making way for the transport of up to six troops. While the Army’s FARA requirements are for an aircraft with a sustained cruise speed of 180 knots and a dash speed of 205 knots, Sikorsky believes it can greatly exceed this goal while at the same time adhering to overall program budget constraints. “We really feel that this will deliver transformational capability to the Army,” said Jay Macklin, Sikorsky business director for Army programs and innovations.
“The reason that we chose this design is that it is really about operational flexibility for the commander,” said Macklin. “The [pilot] side-by-side configuration we chose allows you to have a very large weapons bay.” Despite the aircraft’s width, he said that the overall design is a “very smooth, streamlined aircraft with very little drag. No wings or bumps or anything like that that will actually slow you down.”
Using the S-97, Sikorsky has demonstrated a variety of maneuvers that cannot be accomplished with a traditional helicopter including high agility at low speeds, level body acceleration and deceleration, a turn distance that is half that of conventional helicopters, a cruise speed of better than 200 knots, reverse propulsor to slow descent, nose-down hover for more time on target and precise weapons delivery, and disengaging the propulsor for “whisper mode” to sneak up on targets or reduce noise in cruise flight.
Macklin said Sikorsky is continuing to expand the flight envelope of the S-97 and incorporate useful data into Raider X. To date, the S-97 has flown 180 hours at speeds up to 205 knots. The aircraft also has accumulated 503 ground hours and 2,850 software integration lab hours. “We look at Raider as risk reduction for us. Every hour we fly it, some piece of data comes off of it that feeds into the design and answers a question as we build the [Raider X] competitive prototype [CP].”
Flying the S-97, “We can get answers to our questions today without having to wait a year to fly the CP,” said Pete Germanowski, Sikorsky FARA chief engineer. “It allows us to make more informed decisions earlier in the [design] process.”
The S-97, Raider X, and larger Defiant X being developed for the Army’s Future Long Range Assault Aircraft competition feature Sikorsky’s X2 technology that first flew on a technology demonstrator in 2008 and would go on to achieve 250 knots forward speed. “We wanted something that was fast, but we also wanted something that is quiet,” Macklin said. “When [the propulsor] is cut it becomes very quiet, quieter than a Black Hawk.”
Macklin also noted that Sikorsky has a “full gamut” of autonomous technology, from partial to full, including its Matrix system, that can be incorporated into the aircraft to reduce pilot workload. “The Army is going to decide what level of autonomy they want to settle on. It’s part of this whole digital network with advanced UAVs and drones to achieve that [desired] level of standoff.”
He also said the aircraft’s rigid main rotor system was designed for ease of maintenance. “There’s about half the number of parts on this rotor head than there is on a Black Hawk. We don’t have blade dampeners on an X2 aircraft,” which is the top maintenance driver on a Black Hawk. The design also eliminates one of the gearboxes required to drive the tail rotor. The propulsor itself is not critical to either forward flight or takeoff or landing. Should it fail or be shot off, the aircraft can still achieve a forward speed of 160 knots.