Sikorsky has completed 90% of the construction of its Raider X competitive prototype (CP) helicopter, its submission for the US Army’s Future Attack Reconnaissance Aircraft (FARA) competition, the company told FlightGlobal on 29 June.
That was the assessment of Pete Germanowski, Sikorsky’s chief engineer on the Raider X build, during a tour of the Lockheed Martin subsidiary’s test flight facility in West Palm Beach, Florida. The site, which features a 2,100m (7,000ft) private runway and flight manoeuvre course, is where Sikorsky is assembling its submission for the FARA bid.
The Raider X is a finalist for the FARA contract, going against Bell’s 360 Invictus design.
The proposal is ”like the F-35 for the army”, says Andy Adams, Sikorsky vice-president for future vertical lift. Adams notes that like Lockheed Martin’s F-35 Lightning II fifth-generation fighter, the Raider X is designed to fly and survive in a contested, near-peer combat zone.
Near-peer refers to an adversary with advanced air defences and other modern capabilities. Raider X aims to achieve survivability through speed and manoeuvrability.
It will feature a modular internal bay that can be configured to carry retractable missile pods, an auxiliary fuel tank or seats for up to six dismounted troops.
However, it will still be more than another year before Sikorsky has the chance to demonstrate Raider X. Army budget documents for fiscal year 2023 show that first flight of the FARA programme CPs has been delayed until the autumn of 2023.
The army’s programme executive office for aviation tells FlightGlobal that the shift was the result of pandemic-related delays in producing the GE Aviation T901-GE-900 Improved Turbine Engines (ITEs) that will power both FARA designs, and eventually both the Sikorsky UH-60 Black Hawk and Boeing AH-64 Apache helicopters.
Those delays are now largely resolved. Sikorsky executives say they currently have 98% of parts needed to complete the Raider X build on-hand.
Jay Macklin, FARA programme chief for Sikorsky, says the company is “closely coordinated” with both the army and GE Aviation on the ITE development process.
In the meantime, Sikorsky has been using a different, but highly similar aircraft to refine its Raider X design and gather flight data and pilot feedback.
The Raider X is based on an internally-funded experimental airframe Sikorsky calls the S-97 Raider. It is the fifth-generation in the Connecticut-based manufacturer’s X2 line; which are based around coaxial, dual main rotors.
Another Sikorsky CP, the SB-1 Defiant developed in partnership with Boeing, also shares X2 lineage and similar design features. That platform is a finalist in the Future Long-Range Assault Aircraft (FLRAA) competition, in which the army is expected to select a winner in the coming months.
The Defiant and Raider X are so similar that Macklin says there would be a high degree of commonality in everything from sustainment to pilot training; a point that he notes is a “huge part” of Sikorsky’s pitch to the army for both FLRAA and FARA.
The army currently has separate military occupational specialities for its various helicopter mechanics and most pilots are typically trained for one airframe throughout their career.
That type of commonality is not an army requirement for separate Future Vertical Lift designs.
Macklin says Sikorsky’s FARA team likes to consider the S-97 an “80% prototype” of the final Raider X design. Both feature the coaxial rotors and a rear mounted propeller for generating forward thrust, as well as very similar airframes.
Raider X is roughly 20% larger to account for army requirements like a nose-mounted 20mm cannon, but the flight characteristics are similar enough that Sikorsky has been able to use the S-97 to advance Raider X development, even while the first flight model of that craft is still under assembly.
“It’s a pretty stunning ride when you first get into it,” says S-97 test pilot Christian Corry.
A former US Marine Corps pilot of the Sikorsky CH-53E Super Stallion, Corry says Sikorsky believes the Raider and Raider X will fly very similarly.
He also notes that the coaxial-prupolsor system of the X2 line allows the Raider to fly substantially faster than traditional tail rotor helicopters, whose forward thrust and lift are limited by a physics concept called retreating blade stall.
Another Sikorsky test pilot, John Groth, says the S-97 can reach airspeeds where flying it feels more like “fixed-wing type manoeuvring”.
Groth assesses that the transition from a more traditional helicopter style of flight to the fixed-wing feel happens at an airspeed of around 80kt (148km/h).
The Raider can also fly without the rear propulsor engaged, substantially reducing the aircraft’s noise. The S-97 is noticeably quieter than a UH-60 Black Hawk, even when it flies directly overhead.
Groth attributes this to the lack of tail rotor in the design, which he says is what generates most of the in-flight noise on a conventional design.
Germanowski notes that despite the Raider’s GE Aviation YT-706 engines being less powerful than the ITEs that will ultimately power the Raider X CP, the S-97 is already meeting most of the army’s performance requirements for FARA.
He adds that Sikorsky is not moving slower because of the delay in receiving the final engines from GE.
The company is in the process of constructing a second Raider X test airframe at a facility on Long Island, New York. Germanowski says this will be used for ground testing, but can be made fully-flight worthy if required.
While a final decision in FLRAA is expected before the end of the year, FARA has a significantly longer horizon. The engineering and design phase of the programme is currently slated to run past 2027, according to army budget documents.
Such a long lead time creates risk that the army will cancel FARA altogether, as happened with the Boeing-Sikorsky RAH-66 Comanche that was cancelled in 2004, after the government had spent $7 billion and more than a decade developing the programme.
Find more flight videos of the S-97 Raider here.
