After decades of Pentagon neglect punctuated by false starts on several helicopter projects run by the Army and one each by the U.S. Navy and Air Force, U.S. military vertical-lift aviation is poised to achieve historic advances.
Over the next two years, at least five manned and unmanned advanced vertical-lift technology demonstrator aircraft for the military are scheduled to fly, each offering far more speed and other capabilities over conventional helicopters. Production contracts could follow.
And while so far largely confined to civilian aviation, a flurry of experimentation and development by NASA and the private industry with the emerging breed of electric-propulsion aircraft has begun to attract interest and possible future investment from the Pentagon.
“The Pentagon’s recent upturn in investments in developing new rotorcraft has been a welcome change from the past two decades,” said Michael Hirschberg, executive director of the American Helicopter Society International. “Since the Apache and Black Hawk first flew in the mid-1970s, the only all-new vertical flight aircraft to be developed and fielded by the U.S. military has been the V-22 Osprey.”
The Marine Corps put the Osprey into service in 2007.
The military has long invested far more money in fixed-wing aircraft than rotorcraft — and still does. But in the war years that followed the terrorist attacks of September 11, 2001, leaders in the Pentagon, the military services and Congress awoke to how vital rotorcraft can be. Some also realized that while U.S. military rotorcraft are the best in the world, they are largely based on decades-old technology — and perform accordingly.
That realization took a while to arrive. The first decade of war saw the Army cancel development of the Boeing-Sikorsky RAH-66 Comanche, a stealthy armed reconnaissance helicopter, and use the estimated $14 billion remaining in that program to upgrade existing aircraft instead.
Two projects to replace the Army’s 1969-vintage Bell Helicopter OH-58D Kiowa Warrior scouts were then started and abruptly canceled — the Armed Reconnaissance Helicopter and the successor Armed Aerial Scout. The latter was canceled in 2013 in light of budget cuts and the promise that the Pentagon’s Future Vertical Lift initiative (FVL), a project to develop advanced VTOLs, would ultimately fill the Army’s lightweight armed scout need. In 2009, meanwhile, Defense Secretary Robert Gates canceled the Navy’s VH-71 presidential helicopter program and the Air Force’s CSAR-X program to build new combat search and rescue helicopters.
Against that backdrop (admittedly an easy act to follow), here’s why the future of military vertical lift is looking bright.
Joint Multi-Role Technology Demonstrator Program
The Army-led FVL’s goal is to provide the military with next-generation VTOL aircraft in three sizes — light, medium and heavy — built to perform five “capability sets.” The new attention being paid to advancing military VTOL capabilities is reflected in how the Pentagon and Congress have treated an FVL program to build two Joint Multi-Role Technology Demonstrator (JMR TD) aircraft.
Under JMR TD, Bell Helicopter Textron and a team formed by Lockheed Martin’s Sikorsky Aircraft and Boeing’s Phantom Works are to fly new, faster, more agile manned VTOL aircraft late next year or early in 2018. Bell’s is the V-280 Valor, a tiltrotor smaller than the V-22 that incorporates lessons learned from that Bell-Boeing helicopter-airplane hybrid transport. The Sikorsky-Boeing team is building the SB>1 Defiant, a compound helicopter with coaxial rotors and a pusher propeller derived from Sikorsky’s speedy X2 Technology Demonstrator, but weighing about six times more. Both are expected to be in the 30,000-lb empty-weight range.
“We’ve made a lot of progress in the last year and a half because resources came to bear,” said Dan Bailey, the U.S. Army’s JMR program director. “Congress plussed my line up by about $14 million last year, Congress plussed my line this year by $10 million, and I’m hopeful that they’ll continue to plus us up in the next year.” Those additions brought the JMR TD budget to $56.7 million in fiscal 2015 and $61.3 million in fiscal 2016. The administration has requested $50.9 million for fiscal 2017.
After the JMR TD commenced, the FVL program began writing capability sets specifying performance and other requirements for the different aircraft ultimately to be built. Capability set 1 most closely matches the small, armed reconnaissance aircraft the Army still needs to replace its OH-58Ds. The Bell and Sikorsky-Boeing JMR TD aircraft come “very close” to capability set 3, Bailey said, but are not designed against it “because we didn’t have a defined capability set 3 when we began the design of these aircraft.”
Among its many specifications, capability set 3 calls for a VTOL aircraft that cruises between 230 and 310 kt with a full payload, has an unrefueled combat radius of 229 to 450 nm with payload and can stay on station at least 30 min in a troop-carrying variant. Capability set 3 also requires the ability to hover out of ground effect (HOGE) at 6,000 ft on a 95-deg F day while at the edge of the mission-range radius.
Bell mated the Valor’s wings and nacelles with its fuselage last spring at the company’s factory in Amarillo, Texas, and later added a V-shaped tail, flaperons and “ruddervators.” Vince Tobin, vice president for Advanced Vertical Lift Development, said that after the aircraft underwent stress tests during August in an I-beam structure nicknamed “The Red Iron,” workers were to begin installing the Valor’s gearboxes, engines and rotor blades.
Unlike the Osprey, which has a rear ramp, the V-280 will have side doors like Army helicopters and engines fixed horizontally, rather than swiveling with the rotor nacelle. Those features will allow troops to get in and out safely or fire weapons out the sides of the aircraft after landing, Tobin said.
Scheduled for first flight in September 2017, the V-280 will cruise at its namesake 280 kt, Tobin pledged, and meet capability set 3’s 6,000 ft/95-deg F HOGE requirement – 2,000 ft higher than most military helicopters.
Doug Shidler of Sikorsky and Pat Donnelly of Boeing, program managers for the SB>1 Defiant, said in a joint interview that parts for their aircraft were still being fabricated and tested.
“Assembly will be starting up the latter part of this year,” Shidler said, at Sikorsky’s West Palm Beach, Florida, plant. “Our target is to be flying by the end of the year in 2017.”
Donnelly said the companies are building the Defiant to carry 12 troops in a cabin slightly larger than a Black Hawk’s. “We have speed projections of 250 kt, which is over the 230-kt original spec requirements,” Donnelly said. Shidler added that analysis projects the Defiant will be able to hover out of ground effect at as much as 8,000 ft on a hot day – 2,000 ft higher than the capability set 3 requirement.
The only requirement the Defiant might fail to meet, Donnelly said, is the 229 to 450 nm range with payload. “The only reason that we’re not meeting the range requirement is that we are using a pair of T-55 engines from Honeywell, and their fuel consumption is bigger than the projected fuel consumption for FVL,” said Donnelly. But he said the companies are designing a power system that can meet the range requirement using a more efficient engine.
Bell and Sikorsky-Boeing aren’t the only players in the JMR program. Bailey said he is also funding further research on technologies by two other companies that competed to build technology demonstrator aircraft but weren’t chosen — AVX Aircraft Co. of Benbrook, Texas, and Karem Aircraft of Irvine, California. AVX offered its Coaxial Compound Helicopter and Karem its TR-36 Optimum Speed Tiltrotor.
The JMR program is funding wind tunnel testing of a 1-to-10 scale model of AVX’s design, which features a forward wing or canard, ducted fans on a rear wing and no vertical tail, but vertically angled winglets on its rear wing.
“With those aerodynamic interfaces of ducted fans and multiple moving surface lifting forces, the flight control laws for that aircraft are very complex,” Bailey said. The wind tunnel tests are helping engineers collect data “to verify and validate our engineering tools,” he said, and “facilitate flight control law development that would be useful probably on any other kind of complex multi-lifting surface aircraft.”
Bailey said he hopes to have enough funding to later build a model of the AVX design close to a 1-to-2 scale and test it in NASA’s full-scale wind tunnel at Ames Research Center in California.
Karem Aircraft has JMR funding to fabricate and test an innovative rotor hub that uses electromechanical actuators instead of swashplates to control individual rotor blades. The actuators are powered by rotating generators within the hub. Bailey said he hopes to have funding enough for Karem to build a full-scale rotor and test it on a stand by late 2018.
Other companies, though not participating, are monitoring the FVL program, the schedule of which calls for creating a separate “program of record” beginning this month to develop an aircraft able to perform to capability set 3 specifications. The plan is to send out a request for proposals (RFP) to the industry in early fiscal 2019.
Steve Mundt, a retired brigadier general and former director of Army aviation now with Airbus Group as SVP for government strategy and development, said that while his company sat out the JMR TD competition, Airbus might respond to an FVL RFP.
“You’re not out if you don’t participate in the tech demos, because the tech demos are exactly that — it’s to learn,” said Mundt. “What we’re trying to do is develop independently as much as we can.” Airbus is developing a successor to its X3 technology demonstrator, known as the “X-cubed,” which combines a wing and propellers with coaxial rotors to reach a top speed of 255 kt. “We want to stay attuned as much as we can to what is emerging from the tech demos, and where the U.S. Defense Department will ultimately go with requirements,” Mundt said.
DARPA VTOL X-Plane
A third VTOL technology demonstrator scheduled to fly within two years is an avant garde, hybrid-electric aircraft being developed by Aurora Flight Sciences of Manassas, Virginia, under an $89.4 million Defense Advanced Research Projects Agency (DARPA) contract. The odd-looking LightningStrike, as Aurora calls it, is a 12,000-lb, unmanned craft that will use a 6,150-shp Rolls-Royce AE1107C gas-turbine engine — the same used by the V-22 — to power three 1-MW electric generators. Those generators in turn will power 24 individually controlled ducted fans, 18 of which are embedded in a tilting wing and six in a tilting forward canard used to transition the aircraft from vertical to horizontal flight.
DARPA selected Aurora from four competitors to build this VTOL X-Plane, as it’s called, which must take off and land vertically, hover with greater agility than any helicopter and fly at sustained speeds of 300 to 400 kt. Forty percent of LightningStrike’s weight is to be useful load — fuel and payload in an unmanned aircraft — with payload accounting for at least 12.5% of total weight. Aurora flew an all-electric 1-to-5 scale model last April.
DARPA Aerial Reconfigurable Embedded System (ARES)
Another DARPA VTOL technology demonstrator in the works and expected to fly next year is a 7,000-lb unmanned aircraft that would carry modular “plug-and-play” payload pods for cargo, personnel, weapons, sensors or even a tactical wheeled vehicle. Lockheed Martin is the prime contractor with Essington, Pennsylvania-based Piasecki Aircraft building the aircraft for the ARES, which uses tilting ducted fans to convert from vertical takeoff to horizontal cruise. The idea of ARES, a Piasecki-patented concept, is to vastly increase the mobility and range of small military units.
DARPA/Office of Naval Research TERN
A fifth VTOL demonstrator slated to fly by the end of 2018 is DARPA’s Tactically Exploited Reconnaissance Node (TERN), a drone as big as the Air Force’s 10,500-lb maximum takeoff weight General Atomics MQ-9 Reaper. The fixed-wing unmanned Reaper typically carries sensors, four AGM-114 Hellfire air-to-surface missiles and two 500-lb guided bombs.
The TERN program aims to provide small Navy ships with their own long-endurance drone for intelligence, surveillance and reconnaissance and other missions. Northrop Grumman last year won a $93 million contract to build what DARPA’s website describes as “a tailsitting, flying-wing aircraft with twin counter-rotating, nose-mounted propellers” that would lift the aircraft from a ship deck, orient it for horizontal flight and provide propulsion to complete a mission. “They would then reorient the craft upon its return and lower it to the ship deck,” DARPA said.
The TERN and other VTOL drones are candidates for a new Marine Corps requirement for a shipboard drone called MUX, an awkward acronym that stands for “Marine Air Ground Task Force Unmanned Expedition Capabilities.” But Lt. Gen. Jon “Dog” Davis, deputy commandant of the Marine Corps for aviation, is keenly interested in a competing Bell concept for a new unmanned tiltrotor smaller than the V-280, called the V-247. The number is derived from “24/7,” the time on station the Marines want one or more MUX to be able to provide.
Davis said he wants the MUX to “do everything a manned airplane does — fires, electronic warfare, airborne early warning, protection missions.”
The Marines also want a drone helicopter along the lines of the unmanned K-MAX, the intermeshing-rotor helicopter they experimented with in Afghanistan for cargo delivery to remote bases, Davis said. He added that he envisions using such a craft for a variety of missions — including troop transport or casualty evacuation. Davis doesn’t flinch at the idea of automated or remote-control aircraft carrying passengers.
“I’ve always said before I retire I want to strap myself to the side of that K-MAX and have it take me for a ride,” Davis said. “I’m not joking. I’d do it tomorrow.”
The deputy commandant’s enthusiasm for unmanned aircraft extends to the V-280, he said. “I’ve told Bell I would like it to be manned/optionally unmanned, based on the value of the cargo when I want to fly it,” he said.
Others in the Pentagon are also thinking creatively about VTOL. A new rapid-contracting office called Defense Innovation Unit Experimental, known by the acronym DIUx and designed to help the military connect with Silicon Valley entrepreneurs and their rapid development style, has shown an interest in electric propulsion. NASA, Airbus and a host of small companies such as Joby Aviation and Zee.Aero of California are investing millions in new and revolutionary concepts for electric aircraft.
So far, electric aircraft projects are mostly aimed at civilian missions and exotic ideas such as “urban mobility on demand” — automated electric vehicles providing air taxi service. But DIUx recently issued a request for “solution briefs” describing how to build both an unmanned “persistent heavy-lift drone” to transport cargo and a “manned or unmanned electric-powered vehicle capable of vertical takeoff and landing” to transport passengers or an equivalent payload mass. Remote piloting would be required, DIUx said, “with both autonomous and manual flight control desirable.”
“That was pretty neat,” said Chris Van Buiten, VP of technology and innovation for Sikorsky, who said the company has responded to some DIUx requests for solution briefs, but declined to reveal which ones.
Van Buiten said Sikorsky has set aside an experimental electric helicopter the company developed in 2010 called Firefly but is focusing on automation, including a system to let even nonpilots operate helicopters. But he offered, “Essentially every change and leap in aerospace has been accompanied by, or enabled by, a fundamental shift in propulsion.”
Whatever the future of electric propulsion, the world of military vertical-lift aircraft at last is clearly advancing. At long last.
Sidebar: US Army Awards Contracts For Improved Engine
The U.S. Army on Aug. 22 awarded contracts to General Electric and the Honeywell-Pratt & Whitney joint venture known as Advanced Turbine Engine Company (ATEC) for preliminary design reviews of new-technology, centerline concepts for its Improved Turbine Engine Program (ITEP).
That program aims to put much more capable engines on the Army’s Boeing AH-64 Apaches and UH-60 Black Hawks. GE’s contract is worth $102 million; ATEC’s $154 million.
Both are two-year deals and fixed-price-incentive. After preliminary design review, the Army plans to select a supplier to complete the development and qualification of the ITEP engine. ATEC said that the Army would select from competing design reviews in 2018 and then proceed with a sole developer of the new engine.
A service official said last September ITEP would not be hindered by a continuing funding resolution, a scenario the Defense Dept. again faces as fiscal 2016 winds down. ITEP is not a new start program and thus is not impacted by a stopgap spending measure, which typically prohibits money for new starts. — Rich Abott, Defense Daily R&WI