After reviewing feedback from the US Army in its failed bid to provide a new long-range troop carrying helicopter, Sikorsky says it remains confident that its radical X2 line of coaxial compound rotorcraft are the right fit for the army’s needs.

SB-1 Defiant flight - 12 October 2020

While Sikorsky’s Defiant X lost in the FLRAA competition, the company is competing another X2 design in the US Army’s Future Attack Reconnaissance Aircraft programme

Speaking on 25 April ahead of the annual Army Aviation Association of America conference in Nashville, Tennessee, Sikorsky president Paul Lemmo said the helicopter manufacturer is still committed to delivering an X2 aircraft to the army – a design he calls “transformational”.

“We remain confident and excited about the technology,” Lemmo says of Sikorsky’s line of experimental aircraft.

The X2 design is characterised by a compound coaxial main rotor system to generate lift and forward momentum, augmented by a rear mounted propulsor to provide additional horizontal thrust.

Sikorsky pitched the Defiant X, which used the X2 design, for the army’s Future Long Range Assault Aircraft (FLRAA) competition to replace the Sikorsky UH-60 Black Hawk utility lift helicopter. The company ultimately lost to Bell’s V-280 Valor tiltrotor.

Although a subsequent audit of the army’s decision revealed critical flaws with Sikorsky’s bid submission, Lemmo says the service’s feedback on Defiant X flight performance has reinforced the company’s belief in the X2 design.

“We have many strengths associated with the X2, particularly with the air assault missions,” Lemmo says.

“The feedback we received from the army let us know that the agility, stability and scalability of our X2 can be extremely useful in contested areas, particularly the survivability of [the aircraft].”

While he admits Sikorsky is “disappointed” with the outcome of FLRAA, he notes the company is reviewing the army’s feedback on its FLRAA proposal, with an eye toward strengthening future offerings.

In particular, Sikorsky is now concentrating its efforts on another US Army aircraft development programme: the Future Attack Reconnaissance Aircraft (FARA).

Some 10 years after it retired the Bell OH-58 Kiowa scout helicopter, the army is finally developing a replacement in FARA – which it intends to be a substantial improvement in terms of range, speed and armament.

As in FLRAA, Bell and Sikorsky are again pitted against one another as finalists in the FARA design competition. Bell’s 360 Invictus represents a more conventional approach, using a single main and tail rotor design the company says will focus on reliability and durability.

By contrast, Sikorsky is competing another X2 design – the Raider X – that represents another attempt at the “transformational” approach that was ultimately unsuccessful with FLRAA.

Sikorsky has been flying X2 aircraft for over 15 years, with the first craft of the coaxial-style line lifting off in 2008.

The fourth iteration of the X2 design – the S-97 Raider – has a high degree of commonality with Sikorsky’s Raider X FARA prototype. The company is currently flying the S-97 as a testbed at its flight development centre in West Palm Beach, Florida.

“We know that our FARA offering is going to provide transformational capabilities, at an affordable cost,” Lemmo says.

The |US Government Accountability Office (GAO) review of the FLRAA decision confirmed Sikorsky’s bid offered a substantially lower price than Bell’s offering. However, both the GAO and the army deemed that assessment as unreliable, citing a lack of detail in Sikorsky’s design architecture.

S-97 Raider Test Flight

Source: Sikorsky

Sikorsky’s S-97 Raider testbed is similar in design to the Raider X prototype currently under construction, which the company is competing for FARA

Lemmo argues the better price is the result of a company-wide digital design and manufacturing initiative by Sikorsky parent company Lockheed Martin, known as One LMX.

“All those applications of digital technologies do save money,” Lemmo says.

Such investments allow faster and cheaper completion of development and flight testing, he says, ultimately lowering the total cost of an aircraft.

“Our pricing was reflective of that,” he notes, adding Sikorsky will apply those processes to future programmes.

Lemmo says assembly of the Raider X competitive prototype at West Palm Beach is now 96% complete. Bell has reported similar figures for its Invictus prototype.

Both companies are still awaiting the engine that will power their experimental aircraft, the delivery of which has been repeatedly delayed.

The army required all FARA designs to use the GE Aerospace T901-GE-900 Improved Turbine Engine (ITE). However, GE has struggled to complete design and production of the new engine.

In March, army officials confirmed the ITE delivery had been delayed yet again, likely pushing the first flight of FARA prototypes into 2024. Lemmo says Sikorsky expects that milestone to occur sometime in the summer of that year.

That engine will eventually be integrated into the army’s fleet of UH-60s and Boeing AH-64 attack helicopters.

Elsewhere, Lemmo says Sikorsky is focused on modernisation efforts for the US Army’s fleet of some 2,300 UH-60s and expanding sales of the combat-proven type to more overseas buyers.

While Black Hawk procurement by the army had been expected to conclude in the coming years, the service has indicated it may extend UH-60 purchases as far out as 2033. The army also plans to continue operating the type for decades to come, alongside the V-280 FLRAA.