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Rotor Diameter Scaling Up Success The SB>1 Defiant Joint Multi-Role Technology Demonstrator challenges Sikorsky and Boeing to grow the integrated X2 technologies By Frank Colucci peed and range improvements The SB>1 Defiant JMR Technology Demonstrator scales up Sikorsky X2 rigid coaxial rotor sought by US Army Aviation drove compound helicopter technologies to achieve speed, range and agility far better than SSikorsky, Boeing and their Defiant conventional helicopters. (Sikorsky graphic) team to scale up technologies flown on the 6,000 lb (3 t) X2 and 11,400 lb The MPS summary of FVL-M teams, Sikorsky Innovations vice (5.2 t) S-97 to the 30,000 lb (14 t) class performance includes cruising president Chris Van Buiten previously SB>1 Joint Multi-Role Technology speeds greater than 230 kt (426 stated, “Raider is risk-reduction for JMR.” Demonstrator (JMR-TD). A Systems km/h), vertical takeoff at 6,000 ft/95˚F Sikorsky and Boeing teamed Integration Laboratory (SIL) for Defiant (1,800 m/35˚C) density altitude and up on the SB>1 Defiant in January came on line in December and a a combat radius of 229 nm (424 km) 2013. Boeing program co-director Transmission System Test Bed will run with four crew and 12 troops. The 250 Pat Donnelly said, “When we put in 2016. The JMR-TD due to fly in 2017 is kt (463 km/h) Defiant answers the this together, we were certainly very based on a 2013 Mission Performance specification with rigid coaxial rotors, sensitive to the scaling issues of the Specification (MPS) for a medium-size an integrated tail propeller, optimized X2 technology. Is it exactly an MPS- Future Vertical Lift (FVL) platform to composite structures, fly-by-wire flight responsive vehicle? No — our engines replace Army Black Hawks and other controls and active vibration control are not next-generation engines. The joint-service helicopters. “What we know integrated in an FVL-M-size vehicle. cabin is MPS-compatible. The speeds as MPS and the evolving requirements High lift-to-drag main rotor blades and are MPS-compatible. We’re just going to coming from Fort Rucker are a moving drag-reducing hub fairings address fall short on range.” The demonstrator target right now,” acknowledged the speed challenges of a coaxial will use two Honeywell T55-GA-714A Sikorsky JMR-TD program director Doug compound helicopter. The integrated engines like those now on the Boeing Shidler. Specifics of the SB>1 Defiant technologies enabled the single-seat X2 Chinook. FVL engine requirements are design and manufacturing, and test demonstrator in level flight to exceed yet to be determined, but the Improved plans are also guarded, but Shidler 250 kt (463 km/h) in September 2010 Turbine Engine Program (ITEP), now in added, “We have a lot of parts in flow and began flight testing on the eight- competitive preliminary design, aims at right now, and things are moving along. seat S-97 Raider armed reconnaissance/ a next-generation, 3,000 shp (2200 kW) It is quite exciting to move along with special operations demonstrator in class turboshaft with fuel consumption what’s in the art-of-the-possible for FVL May 2015. Though the S-97 and SB>1 25% better than today’s Black Hawk Medium.” are separate programs with different engine. Donnelly concluded, “We’ve also requirements and different industry 40 JMR Tech Demo Update VERTIFLITE January/February 2016 done a lot of risk reduction so far, so Revisited,” Vertiflite, everything is going well.” Fall 2009). The S-69/ An unpowered Defiant model XH-59A with auxiliary underwent testing in the United jets attained 256 Technologies Research Center wind kt (474 km/h) and tunnel in East Hartford, Connecticut, left Army pilots and the Defiant inlet design was tested enthusiastic about in a Boeing wind tunnel in Seattle, the maneuverability, Washington. Wind tunnel testing handling qualities, complements extensive computer compactness and modeling. Shidler summarized, “The other advantages of results to date have been a Defiant the ABC in low-speed design with all the performance that nap-of-the-earth and was predicted in our proposal, at a lower high-speed cruising weight-empty fraction than previous X2 flight. The ABC designs. That is, it scales as predicted. demonstrator was, “The prediction methodologies nevertheless, heavy we used to size prior X2 designs are and fuel-hungry, the same as those used for the S-97 and exhibited high Raider and are in the process of being vibration levels. confirmed by flight on Raider and Sikorsky design shortly in the wind tunnel using a teams considered Defiant powered model in the NFAC.” conventional Tests in the first half of 2016 at the helicopter, compound National Full-Scale Aerodynamic helicopter, ABC and Complex at Moffett Field, California will tiltrotor solutions use a roughly 1/5-scale powered model to Light Helicopter of the SB>1. Experimental (LHX) Neither the Sikorsky Boeing rigid requirements in rotor coaxial compound helicopter the early 1980s and nor the Bell Valor tiltrotor is an FVL-M briefed their LHX prototype, but the 30,000 lb (14 t) class teammate Boeing demonstrators will uniform government on ABC technology decision-makers on possible approaches in 1985. However, The Defiant builds on the recent flight testing of the X2 Technology to replace today’s 22,000 lb (10 t) former XH-59A Demonstrator and the S-97 Raider light tactical helicopter Black Hawk in the air assault mission: program manager and demonstrator. Both development programs were self-funded by “The Defiant requirements ask for Comanche technical Sikorsky and its suppliers. (Based on Sikorsky graphics; corrected) a 50% higher payload to be carried director Art Linden moments exacerbated by rotor loads twice as far in more stringent ambient recalled, “While all this was going on, applied in opposite directions. ABC conditions, at cruise speeds in excess the Army determined that they had blades, hubs and shafts consequently of 230 knots [426 km/h],” said Donnelly. no need for speed greater than that had to be heavier, and coaxial rotors “These requirements require a design achieved by conventional helicopters. added the weight of duplicate controls. with better efficiency than the current Additionally, they set an arbitrary gross High vibration, like that encountered fleet. The performance advantages weight limit of 7,500 lb [3,400 kg]. Since by the XH-59, today requires engineers over the current fleet extend to better the compound, the ABC and the tiltrotor to add more weight in active vibration maneuverability and agility, the ability all required additional mechanical controls. A compound tail thruster to point the nose at a target in any components to achieve their higher drivetrain and controls like those on X2, flight condition, the ability to back speeds, it became fruitless to try to meet Raider and Defiant introduces additional away from adversaries, and in general, the gross weight limit and provide the weight challenges. greater survivability throughout the ‘bonus’ of higher speeds along with “The tiltrotor presents a different mission. Defiant does this without the all the other LHX requirements. The set of problems,” said Askue. “In hover complication of reconfiguration to go LHX was confined to the conventional and at low speed, the entire weight of fast, with better reliability and lower helicopter configuration.” the aircraft, plus maneuver and safety weight and cost than other concepts.” Former Sikorsky advanced concepts factors, is carried at the wing tips.” engineer — and now Vertical Aviation Where lift loads for fixed-wing aircraft Coaxial Continuum Solutions president — Vaughan Askue are distributed across the span with eight fraction is an important noted, “Both ABC-type rotors and moderate bending loads, tiltrotor lift parameter in the JMR tiltrotors have worse weight fractions concentrates at the tips and requires Technology Demonstration. than conventional helicopters for heavy wing root structures. “In addition, W different reasons.” With no hinges and Sikorsky experience with high-speed you have to add the weight for the coaxial helicopters stretches back to extremely stiff blades, the original ABC trunnions and machinery required the 1970s with the Advancing Blade rotor had an effective offset greater to handle the huge loads from the Concept (ABC) demonstrator (see “ABC than 50%, imposing extremely high hub proprotor while rotating the nacelles Vol. 62, No. 1 JMR Tech Demo Update 41 with a bigger aircraft.” The SB>1 benefits from load. Doug Shidler composite lessons learned in the CH- summarized, 53K and other structures programs. “The “When you Defiant airframe combines a primarily compare Defiant composite structure with metallic and Black Hawk, components in an engineered structure the requirements that minimizes weight. This general issued from the construction is similar to the Raider, but BAA [Broad Area the different requirements for Defiant Announcement] result in a different structure. There are are significantly also payload differences.” different. The Defiant leverages work done on the payload is X2 and Raider rotor systems. “Overall 50% higher in rotor performance, from both figure-of- more stringent merit and lift-to-drag ratio is as good or conditions than a better than Raider,” summarized Shidler. The Sikorsky X2-coaxial Advancing Blade Concept (ABC) was originally Black Hawk… The “The Defiant blades are similar to those proven on the S-69/XH-59, flown between 1973 and 1981. It demonstrated requirement was on Raider as far as general planform 263 kt (487 km/hr) in a shallow dive. (US Army photo) 230 kt or greater. and airfoil choice. However, the Defiant We’re at 250 kt. rotor diameter is larger due to greater and all the other stuff that has to reach We’re doing that while still retaining all payload requirements, and some of the engine and transmissions such as the low-speed handling qualities of a the performance goals of Defiant are fuel, hydraulics, electrical, controls, etc.
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