Speed Vs. Cost
A version of this article appears in the August 25 issue of Aviation Week & Space Technology.
Proving affordability is the biggest challenge facingas well as the / team as they build and fly advanced rotorcraft demonstrators aimed at the U.S. Army’s requirement to replace its Black Hawk helicopters from the mid-2030s.
The two teams have been chosen to fly high-speed rotorcraft in 2017 under the Joint Multi-Role (JMR) technology demonstration, a precursor to the planned Future Vertical Lift Medium (FVL-M) program to replace first the utility UH-60s and later the Army’s Boeing AH-64 Apache attack helicopters. FVL-M could also replace the Navy’s Sikorsky MH-60 Seahawks and the Air Force’s Black Hawk variants.
Between them, the three companies supply most of the’s rotorcraft. For Boeing and Sikorsky, winning one of the two JMR “X-plane” contracts and an FLV-M “Y-plane” fly-off planned for the mid-2020s is crucial to protecting their incumbency with the Army. For Bell, FVL-M would keep the company in the Army business after the OH-58D Kiowa Warrior is phased out.
They faced competition for the demonstrator contracts from two companies offering a “small prime, big team” approach to JMR/FVL—AVX Aircraft and Karem Aircraft. But ensuring the teams had the capability to accomplish the demonstration was a key part of the Army’s evaluation, and the “Big Three” and their suppliers brought significant engineering resources and cost-sharing to the table. Both AVX and Karem are waiting to hear if the Army will fund them to continue some technology development work on their designs.
Agreements in place with all four bidders called for 50:50 cost sharing, but both Bell and Sikorsky/Boeing say industry is investing much more than the government. The reason is the program’s importance to the rotorcraft manufacturers. JMR/FVL will “reinvigorate industry with an opportunity to design an aircraft from the ground up,” says Pat Donnelly, director of the Sikorsky/Boeing JMR team, noting that winning FVL-M would be “a significant continuation of the industrial base built up for Black Hawk and Apache.”
But FVL-M is not a done deal for the JMR winners. The technology demonstration is intended to ensure that advanced rotorcraft capable of at least 230 kt.—50% faster than the Black Hawk—are viable candidates for procurement. However, the Army has yet to decide whether and when to launch a program, or if it will be an advanced rotorcraft, a new conventional helicopter or another upgrade to the UH-60.
“The timeline is a government decision. The best we can do is execute the [demonstration] program well, show the Army the realm of the possible by 2017 and make it more likely they will want to commit,” says Chris Gehler, director of military program operations for Bell. “Affordability is critical.” Cost-prohibitive leap-ahead performance is not a solution, he says. “Everything we are doing is focused on bringing an affordable vehicle to the game. We have to give them a reason to continue.”
For Bell, proving its 280-kt.-cruise V-280 Valor tiltrotor is affordable is crucial because theOsprey has established the tiltrotor’s reputation as capable, but costly to produce and maintain. “With tiltrotor you get inherent performance, but the question is affordability,” says Gehler. “The V-280 is a clean-sheet third-generation tiltrotor. Our focus is on reducing cost and weight, increasing reliability and performance, and making the aircraft come together in the most affordable way.”
The main driver of cost is weight, Gehler says, so the V-280 makes extensive use of composites in the wing, fuselage and V tail. Wing skins and ribs are of honeycomb-stiffened sandwich construction with large-cell carbon cores for fewer, larger and lighter parts. Skins and ribs are paste-bonded together, eliminating fasteners. Costs are reduced more than 30% compared with a scaled V-22 wing, Bell says.
For Sikorsky/Boeing, the 230-kt.-plus SB-1 Defiant is a scale-up of the rigid coaxial-rotor compound helicopter configuration already flown at smaller size with Sikorsky’s X2 Technology demonstrator and being built at a larger size with two industry-funded S-97 Raider light tactical helicopter prototypes, the first of which is to fly by year-end. In addition to affordability, the team will have to demonstrate the utility of the SB-1’s rigid rotors and tail-mounted propeller in the Black Hawk’s transport missions.
“Our hingeless coaxial rotors provide better maneuverability and handling, and allow us to reduce the height between the rotors for lower drag,” says Donnelly. “The goal is long range and high speed without compromising low-speed maneuverability. The Defiant will operate like a helicopter in the landing zone, but have the speed and range of a tiltrotor.” The variable-pitch propulsion will provide acceleration and deceleration, nose-up/-down pitch pointing and can be declutched for safety and quietness in the landing zone, he says.
In the phase just ended, each contender produced two rotorcraft designs, for the air vehicle concept demonstrator (AVCD) and for an objective aircraft meeting the model performance specification (MPS)—the Army science and technology community’s best guess at the FVL-M operational requirements, which will not be set for several more years. “The AVCD is a fully representative, full-scale flight demo of the MPS design to provide the Army with an accurate reflection of what to expect in a future medium-class aircraft,” says Gehler.
The AVCD designs used available technology, including legacy engines:T64s for Bell’s V-280 and T55s for Sikorsky/Boeing’s Defiant. The MPS designs were not limited to what is available now, and could be designed around the Army’s planned fuel-efficient Future Affordable Turbine Engine, for which GE is building a demonstrator. “Composites use in the AVCD fuselage is similar to the V-22, with carbon skins and aluminum stringers. MPS has a completely composite fuselage,” says Gehler.