The US Army's Unmanned Combat Armed Rotorcraft will need high levels of autonomy, while collaborating closely with other vehicles - manned and unmanned

It was always just a matter of time before the US Army followed the lead of first the US Air Force and then the US Navy in exploring the virtues of unmanned combat air vehicles (UCAV). But the army's Unmanned Combat Armed Rotorcraft (UCAR) programme is no "me too" effort. At the same time, the UCAR will be required to operate more autonomously than its fixed-wing counterparts, in a more challenging environment, and collaborate more closely with other vehicles - both manned and unmanned.

Lockheed Martin and Northrop Grumman are working on the preliminary design of UCAR demonstrator systems under contracts awarded by the US Defence Advanced Research Projects Agency (DARPA), which is also leading the US Air Force and Navy UCAV demonstrations, now united as the Joint Unmanned Combat Air System (J-UCAS) programme. "UCAR builds on UCAV, particularly in command and control, but takes the capability the next step, to an increased level of autonomy," says DARPA programme manager Dan Woodbury. "The whole programme focus is on autonomy and collaboration," says Greg Zwernemann, Northrop Grumman's UCAR programme manager. "The key challenge is developing software that will enable autonomy well beyond the current state of the art for unmanned air vehicles."

The UCAR is intended to be part of a manned/unmanned team, operating alongside the army's Boeing AH-64 Apache and Boeing Sikorsky RAH-66 Comanche combat helicopters. "The key element is trusted autonomy, enabling manned assets to trust unmanned vehicles to do tasks for the group in a collaborative fashion," says Dan Rice, Lockheed Martin's UCAR programme manager.

Autonomy scale

On the US Department of Defence's autonomy scale for unmanned systems, where one is a remotely piloted vehicle such as the General Atomics RQ-1 Predator and 10 is a vehicle able to operate entirely on its own, "UCAR will be level 7-9, above the UCAV," says Woodbury. By comparison, Northrop Grumman's RQ-8 Fire Scout rotorcraft UAV, recently selected to be part of the US Army's Future Combat Systems (FCS) network of manned and unmanned ground and air vehicles, has autonomy in the level 3-4 range. "It's a significant advance in autonomy," says Zwernemann.

Exploiting that autonomy, mission planners will assign tasks to both manned and unmanned vehicles, which will have complementary performance, sensor and weapon capabilities. "They will provide top-level tasks to the UCAR, which it will execute with very limited supervision," says Woodbury. While carrying out its assigned task, the vehicle will autonomously detect and avoid obstacles and threats. Helicopters survive over the battlefield by flying nap-of-the-earth, and UCARs will have to operate alongside them, at low altitude, day or night, even in adverse weather, he says.

Mission planning will not involve pre-programming waypoints, as is the case with today's "autonomous" UAVs. "There will be very little need to preplan other than at the mission objective level," says Zwernemann. Software in the vehicle will break the objectives down into actions to be executed. The UCAR will dynamically replan its mission "on the fly" - in real time - working collaboratively with the other manned and unmanned vehicles to reassign tasks based on its condition and the fuel, weapons, and other resources available to the team. "They will not operate on their own, but will make decisions as a team on how to execute what the mission commander wants," he says.

Weapon release will be authorised by the manned assets - which could include airborne and ground command-and-control nodes as well combat helicopters - based on target image "chips" received from the unmanned vehicles' sensors. "They will keep the manned assets safe and aware, but not necessarily in the middle of the action," says Rice. The plan is for UCARs to be managed from any existing command-and-control node, including the US Army's modified Sikorsky UH-60 Black Hawk airborne command centres.

The UCAR is intended for use against camouflaged and concealed targets, rather than tanks in the open, says Woodbury. Programme goals include the ability to identify such targets at two to three times the range of current systems. The sensor suite will be modular, he says, allowing the army to configure vehicles for particular missions, and will include electro-optical, infrared, ladar and radar sensors, as well as off board sources.

Two or more UCARs will be able to co-operate to speed target location and identification. The number of vehicles is one of the variables being left to the contractors - and the teams came up with slightly different numbers in Phase I, says Woodbury - but it is likely that UCARs will operate in "packs" of four to eight. "The army will decide what [unmanned/manned] ratio to use: whether it's five or six to one, or one to one - or whether they use [the UCAR] on its own," he says. "It is like a wingman," says Woodbury.

The unmanned vehicle will be able to designate targets for its own weapons, and those of its manned team-mates of other airborne and ground platforms. Likely armament includes rockets, missiles and a gun, as well as non-lethal weapons. "We will leverage inventory and future weapons, including Hellfire, Advanced Precision Kill Weapon System and Joint Common Missile," says Rice. "We are exploring the possibility of a gun, but there has been no firm decision. A gun has advantages against soft targets, but it adds weight and integration complexity."

While flying autonomously at low level, the UCAR will use onboard sensors to "see and avoid" threats, obstacles and other aircraft. Obstacle avoidance will be a unique capability of the UCAR, says Woodbury, adding: "There will be lots of air vehicles and lots of obstacles, including terrain and wires." And, as Zwernemann makes clear, "it's not only obstacles on the ground, it's collision avoidance too. It's a real challenge."

Second phase

The eight-year UCAR programme entered the second of its four planned phases in July, with Lockheed Martin and Northrop Grumman being selected over Boeing and Raytheon to proceed into preliminary design of the demonstrator system. Lockheed Martin's team includes Bell Helicopter, which has overall responsibility for the air vehicle, while Northrop Grumman is working with helicopter manufacturers Kaman and Sikorsky. Lockheed Martin's Owego, New York-based systems integration division is leading a UCAR effort that includes the company's Skunk Works for multi-spectral survivability, its Advanced Technology Laboratory for sensor data fusion, and its Missiles & Fire Control unit for the sensor and weapon payloads. Owego is Lockheed Martin's "helicopter centre of excellence", responsible for the US Navy MH-60R multi-mission helicopter programme.

The Northrop Grumman team is led by the company's Integrated Systems sector - developer of the RQ-4 Global Hawk UAV - with Electronic Systems responsible for sensors, Mission Systems for mission support and Information Systems for information fusion, while BAE Systems provides mission management and L-3 Communications datalink expertise.

A wide range of air-vehicle concepts were considered by all four teams during the 12-month first phase, says Woodbury. "There were no specifications on the vehicle except VTOL [vertical take-off and landing]. That left a lot of flexibility," he says. "They looked at fan-in-wing, tilt-rotor, helicopter and hybrid. The two winning teams came up with rotorcraft." The vehicles are in the same size range as the Bell OH-58D scout helicopter, Woodbury says, with a "relatively sizeable" internal payload of 230-460kg (500-1,000lb).

UCARs proposed by the two teams are distinctly different, although both share the same hallmarks of stealth design. Lockheed Martin is pursuing a compound helicopter for high speed and survivability. The vehicle has a four-blade main rotor, swept wing and a thruster in place of the tailrotor, for propulsion and anti-torque control. Rice says the design offers "survivability features" and allows the UCAR to fight effectively alongside manned platforms like Apache and Comanche.

"Speed is an important attribute, also agility at relatively gross weight versus a conventional helicopter or tiltrotor. It's a nice balance," he says.

Intermeshing rotors

Northrop Grumman's air vehicle has two intermeshing two-blade rotors, eliminating the need for a tailrotor. Intermeshing-rotor helicopters like Kaman's own K-MAX are known for hover efficiency, and not for speed. But Zwernemann says the design is capable of speeds similar to coaxial-rotor helicopters, which can exceed 200kt (370km/h). "The intermeshing-rotor concept is very flexible, and offers the performance we need to execute the mission," he says, citing its "excellent payload capability".

In an effort to ensure the UCAR is affordable, DARPA has set the goals of a procurement price 20-40% that of the Comanche, or around $4-8 million, and operating and support costs 20-50% those of the Apache or Comanche. "Both teams came within range," Woodbury says. Key to operating costs will the peace time balance between flying the vehicles or storing them and the extent to which simulation can be used to train for manned/unmanned team operations. "We see the UCAR being used on a regular basis, but virtual training is an option," says Zwernemann.

The key challenge for both teams will come well before either of the air vehicles flies. Simulations planned towards the end of the current phase will determine whether UCARs will increase the effectiveness of manned helicopters, or simply increase the workload of their crews. "They will write the software and demonstrate manned/unmanned teaming capability," Woodbury says. "The demonstration will be a big step in deciding what the offloading will be," says Woodbury. "We will put the pilot in the cockpit, fly the UCAR and see what the workload is, how he reacts. The goal is for the manned platform to do everything it was put on the battlefield to do, and for the UCAR to take away from, and not add to, his workload."

The demonstration will involve one simulated AH-64 or RAH-66 and one simulated UCAR, and will be extrapolated to larger ratios. "As the number of UCARs increase, so do the options available. We have to weigh that against the ability to control the vehicles. We will really delve into that in Phase 2," says Zwernemann. At the end of the 15-month second phase, in October next year, DARPA plans to select one team to build and fly two demonstrators, with a first flight in 2006.

If the demonstration is successful, the programme will move into the fourth phase involving "B-vehicle" prototypes with 60-80% of the capability planned for the operational UCAR. This fourth phase is unusual for DARPA, says Woodbury, because it is intended to mature the system so that it can be transitioned to the US Army in 2010 at a technology readiness level (TRL) of 7. Normally the research agency hands over programmes at a TRL of 5-6, he says, but the fourth phase is designed "to effect a successful transition" and a low-risk entry into system development and demonstration.

The UCAR is expected to enter service with the US Army in 2015. By then the J-UCAS programme should have paved the way for the introduction of unmanned combat air vehicles. But achieving the autonomy levels planned for the UCAR poses a challenge that UCAV developers will not have to face.

Source: Flight International