Boeing and Sikorsky have joined forces to develop the SB-1 DEFIANT for the next generation of military forces. The SB-1 is supposed to answer the Army’s need for a new attack/assault helicopter, as well as the Marine Corps long-range transportation, infiltration and resupply missions.
The design will have a cruise speed of 250 kn (460 km/h), but less range due to using the “old” T55 engine. A new engine, the future affordable turbine engine (FATE), is to meet the range requirement of 229 nmi (424 km).
Compared to conventional helicopters, the counter-rotating coaxial main rotors and pusher propeller offer a 185 km/h (100 kn) speed increase, combat radius extended by 60%, and performs 50% better in high-hot hover performance.
Sikorsky-Boeing Defiant Begins Ground Runs
Sikorsky–Boeing states the SB-1 will be quick and nimble, with fast acceleration and deceleration, side-to-side movement, and hovering with the tail up and nose down. The Defiant demonstrator will be powered by the Honeywell T55, which powers the CH-47 Chinook. It will be slightly modified to better operate at slower speeds down to 85% rpm.
In the assault configuration, the Defiant has a crew of four and a cabin equipped for up to 12 combat-loaded troops or eight medevac litters.
It is a vastly different design than the Bell VB-280 which features the tilt-rotor design that they’ve used on their V-22 Raptor aircraft that are currently in use with the Marines and Air Force Special Operations troops.
The Boeing design with the dual coaxial rotors makes it much more agile and maneuverable at low speeds and in tight spaces, where the vast majority of aircraft accident crashes and shoot-downs occur. The theory is, (the tests have still not been validated by the Army), is that with the propulsor in the rear, the pilot can maneuver easily close to the ground without tilting the entire aircraft as they are forced to do with traditional vertical lift helicopters.
The tilt-rotor type like the V-22 was designed to fly long distances with excellent fuel efficiency, not be as agile. However, Bell has stated that the scaled-down version that they are trying to sell the Army handles like a race car.
The Defiant, if chosen by the Army will be a common sight for Special Operations troops in the future, and it is believed its lifespan will reach into the 2030s and possibly beyond.