The Sikorsky-Boeing team behind the SB-1 Defiant demonstrator is pressing on with additional flight tests, five months after submitting to the US Army a proposal for the Future Long Range Air Assault (FLRAA) programme.

During one flight, on 31 January, the SB-1 Defiant demonstrated three capabilities: the ability to fly with one engine; carry a 1,542kg (3,400lb) external sling load at speeds approaching 100kt (185km/h); and ADS-33 Level One flight performance, the Sikorsky-Boeing team says on 17 February. Flight tests took place at Sikorsky’s West Palm Beach, Florida facility.

SB-1 Defiant sling load test c Sikorsky

Source: Sikorsky

The SB-1 Defiant sling load test was flown at 100kt

The SB-1 demonstrator is a co-axial helicopter with a pusher propeller. The aircraft is based on the Sikorsky X2 experimental helicopter that first flew in 2008.

In September, the Sikorsky-Boeing team submitted a rotorcraft design, the Defiant X, based on the SB-1 for the FLRAA competition. FRLAA is a US Army effort to find a next-generation rotorcraft replacement for the Sikorsky UH-60 Black Hawk utility helicopter.

The Defiant X is competing against Bell’s V-280 Valor, a tiltrotor that wrapped up 3.5 years of flight testing in June. The SB-1 did not fly until 2019, due to issues with its composite rotor blade manufacturing process and transmission gears.

The SB-1 demonstrator is powered by twin Honeywell T55 engines. In the recent test flight, to show that the rotorcraft could fly despite the loss of an engine, Sikorsky chief test pilot Bill Fell placed one engine in idle, flew the aircraft at 100kt, made an approach to a hover and then landed.

Hovering with one engine was “a real scenario our troops could face if an engine sustained combat damage”, says Fell.

The Sikorsky-Boeing team announced on 10 February that it had chosen a new 7,500shp (5,600kW)-class turboshaft engine from Honeywell for the Defiant X. That powerplant, the HTS7500, borrows improvements made to the new -714C variant of the T55 engine for the Boeing CH-47 Chinook cargo helicopter, Honeywell said.

In addition to single-engine flight operations, the Sikorsky-Boeing team says that the SB-1 achieved “ADS-33 level one tolerances” by flying slalom manoeuvres at three different speeds between 60kt and 100kt. Aeronautical Design Standard–33 (ADS-33) is a flight performance standard used by the US Army.

The helicopter also used a cargo hook to carry a 1,542kg sling load while reaching speeds near 100kt and at a 20-degree angle of bank.

“This capability will allow Army units to move equipment or build forward operating bases with Defiant like they do today,” Fell said. “These sorties will however be faster as the return trip for the next load will happen at X2 speed – twice the speed of a Black Hawk.”

Separately, Jay Macklin, director of business development for Future Vertical Lift at Sikorsky, told Defence IQ’s International Military Helicopter conference in London on 15 February that the “competitive prototype” of its Raider X helicopter that is being built for the US Army’s Future Attack Reconnaissance Aircraft (FARA) contest is around 70-80% complete. FARA is a US Army programme aimed at replacing the retired Bell OH-58 Kiowa Warrior scout helicopter.

“We are continuing to work really closely with the army to get to the first flight of the aircraft in the next year or so,” says Macklin. “It is coming to life right before our eyes,” he says.

Sikorsky is working with the service to understand “what they are looking for on the competitive prototype programme”.

“The army has certain goals they are setting for us,” he says.

The co-axial compound Raider X will face competition from Bell’s 360 Invictus helicopter in the FARA contest.

While the FARA has always been envisaged as having no personnel on board other than the pilots, Macklin says the Raider X’s large weapons bay could easily be adapted to carry troops, such as special forces operators, if “that’s what the army wants”.