UAVs are often categorized based on performance (linked often to size). There are several categorizations from producers, users and researchers. UAVs can be classified according to the way their flight is controlled, of which there are three methods: pre-programmed; remote control; self-thinking (which can be combined). Each means of control provides both challenges and opportunities.
1. The most basic control is by pre-programmed flight. This is simple, does not need technically difficult and disturbance-sensitive data-links for control, and gives ranges beyond the line-of-sight. However, the system is inflexible. Once airborne the UAV follows a fixed path. It cannot ‘take a second look’ at something that seems interesting. If the UAV needs to fly as low as possible, it is also dependent on good information of the terrain.
2. Remote-control is the most common control system for UAVs. By radio, the operator receives flight data from the UAV and sends flight commands back. The weak points of this system lie in the vulnerability of the continuous radio links, which reveal the positions of both the controller and the UAV, and the fact that radio links limit the UAV’s range. More advanced, less vulnerable radio links and indirect radio links (e.g. via satellites or relay UAVs) are a partial solution.
3. Self-thinking UAVs are still a futuristic option. The technical challenges to develop a fully autonomous UAV are still insurmountable. Nevertheless, an element of self-thinking has been achieved in as much as UAVs are able to react to threats, for example, when attacked by an air-defence missile.
UAVs and UCAVs are themselves just ‘aircraft’ with onboard systems. However, they are usually linked to additional equipment outside, such as the remote-control and launching equipment. In addition, UAVs often have an interchangeable ‘mission package’, which includes the sensors and, if necessary, the link for transferring data collected by the sensors. Together, this equipment forms the UAV system7, the main components.
A UCAV is a sub-category of UAVs. It is basically nothing more than an armed UAV. The border between UAV and UCAV is a thin and grey one. Generally, all UAVs have an inherent combat capacity – one just has to replace a non-deadly payload with a deadly one. The US Predator was modified from a reconnaissance UAV to a UCAV by simply adding Hellfire missiles. UCAVs have evolved, experimentally, when normal aircraft have been modified to operate without a pilot. Iraq is reported to have modified L-29 trainer aircraft into remote-controlled chemical weapon sprayers.
The term UCAV, however, is generally used for a high-performance vehicle, capable of high speed, long range and heavy weapon load – more or less the equivalent of a manned ground-attack or bomber aircraft. The armed Predator, therefore, would not really count as a UCAV, while the Iraqi L-29 modification would be a borderline case.
The first successful use of armed UAVs in combat operations was the attacks carried out by the US against ‘terrorist’ targets in Yemen and Afghanistan in 2002 and 2003. These attacks were carried out with Predator (MQ-9) reconnaissance UAVs modified to carry one or two Hellfire missiles. The use of armed UAVs resulted from the failure of the US to ‘take out’ terrorists, and specifically Osama bin Laden, with cruise missiles. While the cruise missiles worked more or less as advertised, the time lag between identifying a mobile target such as Bin Laden and the actual impact of the missiles was too great.
Ruling out the use of manned reconnaissance and attack systems, the only solution was to combine the detection and surveillance capabilities of a UAV with a weapon. This could either be done by relaying surveillance data to a platform carrying weapons or by adding weapons to the surveillance system. The first option has already been used by Israel in actions against targets in Gaza and Lebanon: UAVs would patrol and identify targets and manned aircraft would fire stand-off guided missiles to attack the target. Since the platform (usually an aircraft) carrying the missile was further away from the target than the UAV, there still remained a gap between target identification and the missile hitting. It also meant that a manned platform would have to be within missile range of the target.
The US, however, chose to arm the UAV itself, thereby further closing the gap between target identification and a missile hitting it, and providing the option to do all this from a distance of up to several hundred kilometres. Adapting a rather large UAV, such as the Predator, to carry a light armament did not prove too difficult. The Predator was modified, tested and brought into action within months. It gave the US new options to identify and attack time-sensitive targets without having to risk manned aircraft over ‘enemy’ territory or in politically sensitive airspace. The armed Predator proved so successful that a new version was ordered almost at once. This much improved version - Predator-B (MQ-9B) - is now being acquired, capable of carrying up to 450 kg of missiles or bombs as well as air-to-air missiles to defend itself against interception. This new Predator has an endurance of almost two days.
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