An update on Boeing Sikorsky SB-1 Defiant experimental multi-mission helicopter was published at the end of June 2018. The helicopter is offered to US Army for the FVL-M (Future Vertical Lift-Medium) program. Final preparations for test flight are currently underway in Palm Beach, Florida. Flights are to start in 2018.

Common elements of the SB-1 Defiant transport and assault variants are, for example, propulsion, active vibration control, composite body and control system /Graphics: Boeing

Common elements of the SB-1 Defiant transport and assault variants are, for example, propulsion, active vibration control, composite body and control system /Graphics: Boeing

SB-1 Defiant is to lift off for the first time after the ground tests are finalized, stress levels are calculated and the key components are checked at the testing station. Coaxial, 2-rotor design with opposite, rigid rotors and a pushing propeller is to be more effective than solution used in a tiltrotor crafts.

The only competitor of the Boeing – Sikorsky in the FVL-M program (Previously known as JMR TD – Joint Multi-Role Technology Demonstration), is the Bell V-280 Valor tiltrotor craft. It`s prototype is currently in the advanced stage of flight testing. The service commencement of the FVL-M is planned for the 2030. Newly designed aircraft is to replace the UH-60 Blackhawk helicopters.

Another participants of the FVL program are the AVX Aircraft with their tail-less, coaxial JMR helicopter and the Karem Aircraft with TR36TD OSTR (Optimum-Speed TiltRotor) craft. USA`s Department of Defense also has plans for procurement of a heavy helicopter for the FVL-H (Future Vertical Lift – Heavy) program. Due to planned modernization of the CH-47F Chinook fleet the FVL-H program won`t happen until 2060.

Analysis
The SB-1 Defiant in transport variant was unveiled in 2014 and was based on experiments with the Sikorsky X2. On the 10th of April 2017 an assault version’s concept was presented. It would replace the AH-64 Apache and has a tandem-style cabin, armament pylons and a cannon in the front of the craft`s body.

Common elements for both variants include propulsion, transmission, fly-by-wire system, folding main propeller, pushing propeller, active vibration control system, tail, control surfaces and a composite hull. Transport variant will have a compartment for additional passengers, side-gunners’ stations and an optional medevac equipment.