Boeing/Sikorsky SB-1 Defiant, A Possible Replacement for the Blackhawk

The Army is looking to replace their fleets of the aging UH-60 Blackhawk vertical lift helicopters and wants their replacements, with an eye toward possible conflict with Russian or Chinese forces to be bigger, faster and much more maneuverable.

The Army is calling this new development the Future Long-Range Assault Aircraft (FLRRA) and it is designed to go faster, over longer distances and maneuver in tight spaces against much more advanced Russian or Chinese air defense systems than what our troops are currently encountering.

This will be an added area of concern for future Special Operations troops who will be tasked with flying into much more dangerous territory behind the enemy’s main line of defenses.  

Boeing and Sikorsky (owned by Lockheed-Martin) 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.

Boeing has stated that the commonality between the attack and assault aircraft developed at 85 percent which will reduce life-cycle costs and development. The Defiant utilizes “two coaxial rotors on top that rotate in opposite directions, the extra lift from each rotor’s advancing blade balances out the diminished lift from the opposite side’s retreating blade to eliminate retreating blade stall.”

To provide the forward thrust for flight, in the aft of the aircraft, Boeing has mounted a pusher propeller, allowing the aircraft to fly nearly twice as fast and twice as far as today’s UH-60 helicopter. This system allows much greater maneuverability and agility including hover, low-speed flight, and high-speed flight.

The Defiant has retractable landing gear, reducing drag hence higher top speeds with greater fuel efficiency, increasing aircraft’s range. The twin-rotor system minimizes rotor downwash as troops embark/disembark, and Boeing is also claiming a “dramatically reduced acoustic signature”, something that the tilt-rotor aircraft don’t do well. When transporting the Defiant, the top rotors can be folded back, allowing it to be stored and transported easily on current Air Force transport platforms.

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.

The co-axial blades have already been used on Boeing’s X-2 helicopter. However, it is the rotor blades that was the slow-up in development, which the SB-1 is nearly a full year behind Bell’s VB-280 aircraft.

The rotor blades have to be extremely rigid to withstand to handle the vibration. The Army had asked Boeing to conduct a new manufacturing process called automated fiber placement. That took a while to master, and if the Army decides to buy the SB-1, this will drive the cost lower and increase the speed and efficiency of the production.  

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 Bell VB-280 flies at a top speed of 280 knots (hence the 280 name) or about 322 miles per hour. The SB-1 flies at about 250 knots or 288 miles per hour, slower by a bit for sure. The current UH-60 has a top speed of about 183 miles per hour.

Boeing, in their own press release, made a case for the Defiant with the following criteria:

• X2 Rotor System: A rigid, co-axial rotor system with pusher propulsor that provides improved mission objective capability, reduced wear on parts and systems, increased reliability and lower total lifecycle costs
• Maneuverability and Agility: Improved agility and flight control augmentation allow tight assault formations with close proximity landings to deliver embarked troops as a cohesive unit and minimize exposure to hostile threats
• Speed and Range: Twice the speed and distance of today’s conventional helicopters while increasing the overall maneuverability and agility needed for the US Military’s various missions
• Survivability: Propulsor thrust coupled with large angular rates and precision attitude control enable the SB>1 DEFIANT™ to rapidly and precisely displace the aircraft position or flight path in response to threats or evolving tactical environments
• Lethality: Rapid and precise acquisition of targets and prolonged engagement windows
• Deployability: When folded for shipboard stowage, the SB>1 DEFIANT™ fits the footprint of a folded AH-1

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.

Boeing has produced a video on what it will look like in the future:

Photos: Boeing