The US military is showing increased interest in vertical take-off and landing (VTOL) unmanned air vehicles (UAV), going beyond current helicopter-derived UAVs such as the Northrop MQ-8 Fire Scouts ordered by the US Navy.
The most dramatic innovation to date is the Bell 247 Vigilant UAV, first announced on September 22, which adapts the company’s advanced tiltrotor technology to an unmanned design: a single-engine 29,000lb (13,150kg) tiltrotor that builds on Bell’s earlier Eagle Eye tilt.
Bell Helicopter has recently announced an unmanned tiltrotor, the V-247 Vigilant. The manufacturer says the design will combine long endurance and speed with the ability to operate without a runway
(such as in maritime environments or in contested areas with no secure runways). It said the V-247 is “designed to address the evolving demands of the military and transportation sectors for unmanned aircraft for a shipborne UAS platform”. The aircraft is being designed for electronic warfare, intelligence, surveillance and reconnaissance, escort, C4 (command, control, communications and computer), persistent fre, and tactical distribution. Bell Helicopter says the design, which could be ready for production in 2023, will satisfy the spectrum of capabilities outlined in the 2016 Marine Corps Aviation Plan, and that it will leverage the experience of the V-22, UH-1Y/AH-1Z, and V-280 Valor for the V-247’s development.
The V-247 will have a 65ft (19m) wingspan and a 30ft (9m) rotor diameter. Its cruise speed will be 250kts (462km/h), endurance speed 180kts (333km/h) and maximum speed 300kts (555km/h) at maximum continuous power. It will offer a 29,500lb (13,380kg) maximum gross weight and be able to carry 13,000lb (4,535kg) of fuel, sensors and armament. Range will be 450 nautical miles (833km) and time on station 11 hours.
Folding blades will ensure compatibility with hangars on DDG ships, and two V-247s will be able to be transported in a C-17. The aircraft will have a modular payload system, a redundant flight control system, and an electro-optical and targeting system. The bays on the aircraft will be able to carry sensors, fuel, sonar buoys, LIDAR equipment, radar, a Mk50 torpedo or Hellfire missiles.
Designed as a company-funded independent research and development effort and capable of operating from ships, the V-247 is intended for the US Marine Corps, providing greater UAV capability than its current RQ-7 Shadow UAVs.
The US Marine Corps has budgeted the Marine Unmanned Experimental (MUX) programme for a VTOL UAV to start in FY2018. MUX is required to have performance (including armament) comparable to the US Air Force General Atomics MQ-9 Reaper. In addition to the V-247, MUX competitors are likely to include the Northrop Grumman Tactically Exploitable Reconnaissance Node flying wing (developed under a Defense Advanced Research Projects Agency contract) and the Karem Swift tiltrotor.
The US Marine Corps issued a request for information-(RFI) linked to an ambitious programme to deliver a ship-based, vertical take-off and landing unmanned air vehicle for use from the latter part of the next decade. As outlined on 8 March 2018, the Marine Air Ground Task Force – Unmanned Expeditionary Capabilities (MUX) activity would field an aircraft capable of operating autonomously from an amphibious assault ship and providing persistent multi-role aerial coverage from up to 350nm (648km) away.
Expected roles would include early warning defence, reconnaissance, electronic warfare, and communications relay capabilities, according to the USMC’s request, with a secondary priority being offensive air support.
The MUX aircraft will have an unrefueled combat radius of 350- 700nm, and be capable of achieving cruise speeds of 200-300kt (370-555km/h) with a full payload. This performance will complement the long-range capabilities of the USMC’s Lockheed Martin F-35B/Cs, Bell Boeing MV-22, Sikorsky CH-53K and Future Vertical Lift rotorcraft, the RFI shows.
Since revealing its MUX ambitions in August 2016, the USMC has attracted interest from four major US contractors. Bell is developing the V-247 Vigilant tiltrotor, Boeing a tail-sitting flying wing dubbed the MUX-1, Lockheed’s Skunk Works unit – partnered with Piasecki Aircraft – a tilting duct fan aircraft named ARES, and Northrop Grumman the Tern tail sitting flying wing.
Bell V-280 Pushing the envelop
Since its first flight on December 18, 2017, the Bell V-280 Valor tiltrotor Joint Multirole-Technology Demonstrator has achieved more than 125 hours of rotor turn time and nearly 45 hours of flight time in a test programme currently based at Bell’s Amarillo, Texas, facility (planned to move to Fort Worth, Texas, later this year).
To date, the V-280 has undertaken and demonstrated ground taxi, hover taxi, low altitude hovering manoeuvres, including 360 pedal turns and forward/aft/lateral repositions, 60kts (110km/h) roll-on landings, and forward flight out to 195kts (360km/h). The first cruise mode flight took place on May 11 and during July and August US Army test pilots flew the V-280 from the Amarillo facility.
By the end of the test programme, it will have demonstrated its designed maximum speed of 280kts (518km/h). Next steps include making the retractable undercarriage fully functional, developing the designed-in pilot-augmentation functions, using the Lockheed Martin Pilot Distributed Aperture System that provides 360° vision to the pilots (based on the system onboard the F-35 Lightning II) and using the head-up display and head down display.
Built as a technology demonstrator, the V-280’s design features are intended to increase performance and lower costs for production aircraft. These include all-composite wings and rotors and a straight wing design without sweepback or taper.
This is intended to lead to a unit price, in production quantities, of about $30 million in current year dollars, some 50% greater than current UH-60 versions. The improved performance of the Future Vertical Lift (FVL) rotorcraft is not going to make them cheap to buy. While price has not been identified as a major determinant, the scope of potential FVL procurements is likely to make it an important consideration.
The V-280’s two General Electric T64-GE-419 engines, as currently used to power the Sikorsky CH-53E Super Stallion, are likely to be replaced by engines with improved fuel consumption once these become available. Unlike the older Bell-Boeing V-22 Osprey tiltrotor, the V-280’s engine nacelles do not change positions between vertical take-o and cruise flight, just its rotors. This requires a sophisticated clutch and gear system and transmission. The V-280 reportedly offers improved low-altitude manoeuvrability and reduced downwash and acoustic signature.
Bell is positioned to use the technologies being demonstrated on the V-280, designed to FVL Capability Set 3, on smaller platforms. It is currently working on a tiltrotor UAV, the V-247 Valiant, intended to meet the US Marine Corps’ Marine Unmanned Expeditionary requirement (operating the Osprey has made the Marines enthusiastic about tiltrotors). A scaled-down V-280 has been mentioned as a possible Future Attack Reconnaissance Aircraft Competitive Prototype.