The SB-1 Defiant coaxial compound helicopter prototype, built by a Sikorsky [LMT]-Boeing [BA] team, broke contact with the ground on March 21 for the first time.
Neither company released much information about the flight, although a video of the event at Sikorsky’s West Palm Beach, Florida, flight test facility shows the aircraft in a low-level hover over the runway, in slow forward and backward flight and pivoting around its main rotor mast before making a gentle landing.
The video shows off Defiant’s coaxial, rigid-rotor design in detail. It has eight rotor blades, four each on two counter-rotating main rotors. An eight-bladed pusher-propulsor — basically a backwards propeller — is affixed to the aft fuselage to provide forward thrust. The blades’ pitch is variable to maximize thrust and perform quietly at high speed.
Defiant is designed to fly at twice the speed and range of today’s conventional helicopters and offers advanced agility and maneuverability. It will help inform the next generation of military helicopters as part of the U.S. Army’s Future Vertical Lift program.
Its maiden flight comes as a better-late-than-never moment for the Defiant, which is participating in the U.S. Army’s Joint Multirole Technology Demonstration(JMR-TD) program. Prototype aircraft were originally scheduled to fly by the end of 2017. The Defiant team then set a goal of flying in 2018, but scrapped plans near the end of the year. Its direct competitor, Bell’s V-280 Valor advanced tiltrotor, celebrated a year of flight testing on December 18.
Sikorsky has been flying Defiant’s smaller cousin, the S-97 Raider, for nearly three years. That aircraft, which has the same basic configuration as the SB-1, is aimed at satisfying the Army’s need for a Future Armed Reconnaissance Aircraft (FARA) that would fill the void left by retiring the OH-58D Kiowa Warrior armed scout.
“Defiant is designed to fly at nearly twice the speed and has twice the range of conventional helicopters while retaining the very best, if not better low-speed and hover performance of conventional helicopters,” said Dan Spoor, vice president, Sikorsky Future Vertical Lift. “This design provides for exceptional performance in the objective area, where potential enemy activity places a premium on maneuverability, survivability and flexibility. We are thrilled with the results of today’s flight and look forward to an exciting flight test program.”
Data from Defiant will help the Army develop requirements for new utility helicopters expected to enter service in the early 2030s. This flight marks a key milestone for the Sikorsky-Boeing team and is the culmination of significant design, simulation and test activity to further demonstrate the capability of the X2 Technology.
The Army has cut the budget for JMR-TD to just $10 million in its 2020 funding request to Congress, down from more than $140 million in the current fiscal year. Army budget documents, which realign all Future Vertical Lift development efforts under a single funding stream, state that the service considers JMR-TD effectively complete as of Oct. 1, though Defiant has only just flown.
With so much flight testing under Bell’s belt, company officials have suggested they will curtail further test and demonstration without future funding from the Army.
“The design and development of Defiant has revealed the capability advancement that is truly possible for Future Vertical Lift,” said David Koopersmith, vice president and general manager of Boeing Vertical Lift. “Clearly, the performance, speed, and agility of Defiant will be a game changer on the battlefield and we look forward to demonstrating for the U.S. Army the tremendous capabilities of this aircraft.”
Defiant, like the V-280, is aimed at satisfying the Army’s requirement for a Future Long-Range Assault Aircraft, or FLRAA, that would be about the size of a Black Hawk but with superior range and speed.
Sikorsky maintains its X2 Technology is “scalable to a variety of military missions such as attack and assault, long-range transportation, infiltration and resupply.” Defiant is the third X2 aircraft the company has built in less than 10 years. But Defiant’s unique composite rotor blades production process proved a more difficult than anticipated nut to crack. During runs of the ground-based engineering test bed, engineers also found that some of the transmission gears were not sufficiently hardened to perform as expected.