Defense Media Network

UCAVs: Considering the Next Step


Unmanned combat air vehicles (UCAVs) first came to prominence in the United States during the attack on Afghanistan, when Predators armed with Hellfire missiles were used to attack particular insurgent leaders. The unmanned Predator offered considerable endurance, so it could loiter, waiting for, say, a vehicle carrying known targets to appear, then attack on command. Predator was a remotely piloted attack airplane. It and its successors are now widely used in Iraq and Afghanistan, and the Israelis have used equivalent aircraft in places like Gaza.

In each case, the airplane has relatively low performance, hence can loiter for a long time, and it can also observe a particular area on a protracted basis. No human pilot would want to do anything that hazardous (not to mention that fatiguing). The remote operator’s ability to remain alert (through replacement if necessary) for a protracted period may be quite as important as the airplane’s ability simply to remain in the air for a long time. Any aircraft loitering in a limited area is vulnerable to enemy fire, but the loss of a UCAV is not nearly so serious as the loss of a manned airplane. To date, then, UCAVs have been attractive both because they offer something manned aircraft do not (protracted endurance over a target area) and because they do not hazard pilots. The great question is whether future UCAVs can offer more.

In December 2008, Northrop Grumman rolled out the first X-47B, the air vehicle of the U.S. Navy’s Unmanned Combat Air System – Demonstrator (UCAS-D). X-47B is expected to fly some time in 2010. Unlike Predator and its various derivatives, X-47B is a relatively high-performance attack bomber, comparable to the Navy’s Hornet (but subsonic rather than supersonic). It has a stealthy airframe and internal space for two large guided bombs. Although the prototype lacks additional external hard points, presumably they can be added. Like a Hornet, X-47B has a radar (in its case, a multi-role fixed array) as well as some electro-optics. It is about the size of a manned carrier attack bomber, and in production quantities, it would probably cost about as much. All of that makes it a potential competitor with the emerging F-35 Joint Strike Fighter (JSF). How (and whether) that competition is resolved depends on whether UCAS-D performs as hoped, and also on whether the new potentials associated with its unmanned status are worth the radical change in policy involved in replacing some or all planned JSFs with unmanned aircraft.

Northrop Grumman UCAS X-47B Air Vehicle-1. The Navy plans to test the aircraft’s carrier suitability in 2010. Northrop Grumman photo by Chad Slattery

The UCAS-D designation emphasizes two vital features of the program: that the aircraft is part of an integrated system and that it is intended to demonstrate something not previously done. Unlike a Predator, X-47B is intended to be semi-autonomous, as are several other current unmanned aerial vehicles (UAVs). It is assigned a flight plan and an objective, and it flies itself from waypoint to waypoint. If something goes wrong, or if the situation changes, the operator can assign a new flight plan, but he never actually flies the airplane. X-47B is conceived as one unit of a swarm of such aircraft, which would be tasked collectively. The whole swarm might orbit waiting for orders. The swarm operator would assign it an objective. Communicating among themselves, the aircraft of the swarm would decide which one (or ones) should attack. As aircraft of the swarm used up their fuel and weapons, they would be replaced, the swarm itself operating for an extended period (not least because it would not be affected by pilot fatigue). The idea of such a swarm, operating under broad instructions, seems to be more and more accepted within the naval command and control community. It applies to many kinds of unmanned platforms, not only to aircraft.

This kind of operation is radically different from the way the U.S. Air Force currently operates its Predators. The Air Force argues that each individual UAV, or at least each UAV operating in the same air space as manned aircraft, needs its own dedicated pilot. Over the past few years, for example, it has devoted considerable resources to developing a special ground cockpit for UAVs. UCAS-D and other semi-autonomous UAVs require an autonomous means of detecting and evading nearby aircraft, or else they must operate well away from manned aircraft. Advocates of autonomous UAVs claim that they are very close to such capability, and in any case, that pilots may not prove to be very effective UAV operators. For example, a Predator crashed in Afghanistan because its remote pilot-operator tried to recover from a stall the way he would have in his previous manned airplane, an F-16. Predator was so different that the pilot’s technique made the problem worse.

The demonstration issues are successful UAV operation on and around a carrier flight deck and successful air-to-air refueling. Both are very

One of the major challenges to operating a UCAV from a carrier will be deck handling, such as loading the aircraft onto a catapult, as depicted here. Image courtesy of Northrop Grumman.

important, and both present some difficulties. A crowded carrier flight deck is a very demanding environment, and a carrier pilot responds to numerous fairly subtle cues by flight deck personnel as he maneuvers his airplane. That is aside from the skill involved in landing the airplane on the carrier as it pitches and rolls. Unless UCAS-D can accomplish both deck handling and landing, it is useless to the Navy.

In both cases, there is some reason for optimism. For deck handling, a simple but inelegant solution would be to install a rudimentary set of controls under a fold-down panel atop the UCAV; a deck crewman would climb aboard as soon as it landed and was arrested, and control it on the flight deck. The problem for any other solution is that the same carrier must operate both manned and unmanned aircraft, so however the UCAV operates on deck must be compatible with the method now used to control manned aircraft. If the price of admission for UCAS is to redesign the flight deck control system used by the majority of naval aircraft, UCAS will not be adopted. Solutions commonly discussed require UCAS to interpret standard hand control signals autonomously or semi-autonomously.

As for landing on the carrier, carriers currently have automatic landing systems. Pilots dislike them, but better ones have evolved over the years, and it seems likely that some version of the current system, in which a computer on board the carrier is linked to the flight control computer of the approaching airplane, will work.

Then there is air-to-air refueling. One of the great advantages offered by a variety of unmanned aircraft is long endurance, unlimited by pilot fatigue. In fact, endurance may be the only unique advantage such aircraft offer. Really long endurance would, for example, allow a carrier to maintain a swarm within striking distance of enemy targets while the carrier herself remained far away, beyond the range of most or all enemy anti-carrier weapons. The stealthy design of the X-47B would make that swarm survivable despite proximity to enemy air defenses. The United States already exploits long UAV endurance in its use of Predator UCAVs, and also in many reconnaissance UAVs, such as Global Hawk. There is already a project to demonstrate aerial refueling of a Global Hawk. Presumably much the same technology would apply to X-47B. The X-47B design provides internal plumbing that would allow the aircraft to carry fuel instead of bombs in the internal bays, so the aircraft could buddy-refuel. Without aerial refueling, X-47B would still have a longer effective endurance than a manned airplane (simply because it would have no tired pilot aboard), but the difference from a manned bomber would be far less striking.

A DARPA/NASA effort demonstrated the first autonomous in-flight probe and drogue refueling in 2006. Note the pilot and co-pilot are both “hands off” as the F/A-18 flies its own probe into the drogue. Photo courtesy of NASA Dryden Flight Research Center.

If both carrier operation and refueling are demonstrated, X-47B or a successor will be a candidate naval attack aircraft, but that will hardly ensure that it is adopted. Will it be worthwhile? There are really two questions. One is whether the pilot of such an aircraft performs vital functions that the unmanned system cannot match, in which case some or all attack aircraft should be piloted. The second is whether there is some economic reason that would impel the Navy to make the radical shift. Military organizations tend to be conservative because they know that they have to pay in blood for mistaken innovations. Not all new attractive ideas turn out to be very good once subjected to the stress of combat. Theoretical attractiveness may be deceptive.

Readers may be surprised that the United States already relies relatively little on the judgment of attack pilots. That is not to say that we have moved to some kind of robotic warfare, but rather that the vital element of human judgment has moved largely to the data fusion centers that assign targets – typically by their coordinates rather than by the appearance that pilots can use for targeting. This evolution began in the late 1980s, and it is associated with the dramatic rise of GPS-guided bombs – i.e., of bombs that fly to preassigned target positions. There are, of course, exceptions. In Afghanistan, aircraft are routinely ordered to attack those firing on them. The logic is that such tactics uncover enemy forces. The drawback, revealed when two Air National Guard pilots bombed some Canadian troops, is that the pilots are rarely aware of the precise positions of those they attack, hence cannot know whether they are inside or outside free-fire zones. It probably takes a ground controller to know that. The evolution toward assigned targets is also due to the kind of war we are now fighting, in which targets that matter are quite difficult to distinguish from the air, but may be quite evident from intelligence and sensor data.

Even when the character of the targets may be obvious from the air, as in distinguishing tanks from, say, school buses, pilots may mistake their positions and attack the wrong targets. The one kind of mission that does not fit the preassigned category is armed reconnaissance, but it can be argued that splitting roles between hunting UAVs reporting back to controllers and attacking UAVs striking on the basis of their data would be acceptable.

On the other hand, human judgment applied on the spot is very important for fighter pilots in the frequent situations that are not quite war but also not quite peace. Is that airplane approaching the fleet a hostile bomber or an innocent airliner? If an airliner does not seem to respond to a challenge, are the pilots otherwise absorbed (as in the recent incident in the Midwest where commercial pilots unwittingly overflew their destination by 150 miles) or has the airplane been hijacked, and is it intended to crash into a city? Pilots don’t always get it right, but this is not the sort of judgment call to be assigned to a machine or to a distant controller (whose communications may fail at a crucial moment).

Even so, why switch from manned aircraft, which work reasonably well, to unmanned ones? The crucial argument is probably financial. Manned

While there are many challenges associated with operating UCAVs in non-permissive airspace, the benefits of a swarm of UCAVs that could attack targets without risking a human pilot are obvious. Image courtesy of Northrop Grumman.

aircraft seem less and less affordable, which really means that we can afford fewer and fewer of them. Equivalent unmanned aircraft would cost about as much to buy, but that is only part of the financial story. Most of the money spent on a manned airplane during its lifetime is spent after the airplane is bought. It has to fly frequently, whether or not it is needed for combat, to keep its pilot proficient. The need to maintain proficiency also considerably increases the number of airplanes of any given type that have to be bought in the first place. For example, the Navy operates a given number of carrier air wings but plans to operate a smaller number simultaneously – say, 10 air wings to maintain the ability to deploy six at any one time. The total of 10 is needed to make sure that all operational pilots are proficient.

If the Air Force is right, and every unmanned airplane needs its own pilot, there is not all that much difference between a manned and an unmanned force. The pilots of the unmanned aircraft still must maintain proficiency. They may not have to be forward deployed (the Air Force controls its Predators from a base in Nevada, although the aircraft themselves operate over Iraq and Afghanistan), but they are still needed in considerable numbers. However, if the aircraft are semi-autonomous, as seems increasingly to be the rule, then proficiency flying is pointless. In the Navy case, not only are 10 operational carrier air wings needed, many additional aircraft are needed for pilot training. Switching to something like UCAS might save more than half the money normally spent buying aircraft (or, conversely, about twice as many might be available for combat), plus a larger sum that would normally go for proficiency, as opposed to combat, flying. The cost of maintaining a large carrier force would be cut dramatically – which would be quite attractive, as carriers offer the United States some very important advantages.

There is another way to look at this choice. How much difference is there between a swarming UCAS and a loitering missile like Tactical Tomahawk? The main difference may be that the missile is not recoverable. Like the missile, a UCAS is sent to a designated target. Both are assigned flight plans, but neither is controlled by a full-time pilot. Another difference is that the missile is difficult to transfer at sea, which is why U.S. missile ships typically fire off all of their Tomahawks and then withdraw to a base to reload. By way of contrast, carriers can take both their aircraft and their weapons on board at sea, hence can be kept in action over a protracted period (the key for weapons is that the carrier takes on her weapons horizontally, through her side elevator openings; missile ships have no similar facilities for their vertical launchers). In effect, UCAS aircraft would be cross-decked like missiles if there were not enough for every ship capable of operating them.

In the past, radical changes to military organizations have been accepted because existing methods and weapons proved inadequate and because existing ones were no longer affordable. Existing manned aircraft work (though not always), but pilot fatigue seems to be a more and more important factor as targets are more difficult to distinguish and as decisions concerning whether to attack hinge more and more on a mass of information not really easily accessible by a pilot. One reason the Joint Strike Fighter is becoming so expensive is the insistence on providing the pilot (as decision-maker) with so much information. The story of the JSF may actually be read to say that manned strike aircraft are no longer the affordable bargain that they seem to be. Conversely, as new attack aircraft cost more and more, we may find ourselves forced to look at alternatives. We already rely heavily on missiles, and it may be that the only barrier to greater reliance is that the missiles are not recoverable. If – a major if – UCAS-D works as advertised, we may be at the point at which manned strike aircraft are no longer as attractive as unmanned ones, and the UCAV revolution may take off.


Norman Friedman is an internationally known strategist and naval historian. He is the author of...