The usefulness of UAVs for aerial reconnaissance was demonstrated to the United States in the Vietnam War. At the same time, early steps were being taken to use them in active combat at sea and on land, but unmanned combat aerial vehicles would not come into their own until the 1980s.
History
UAVs, such as the Northrop Falconer, had been developed for battlefield reconnaissance beginning in the 1950s, but these machines saw little or no combat service. Israelis pioneered the operational use of battlefield UAVs in the early 1980s, during their operations in southern Lebanon. Very few of the technologies they used were all that new, but the Israelis finally achieved the proper formula for operational success, using their battlefield UAVs to help destroy Syrian surface-to-air missile sites and assist in other combat operations.
With the successes in southern Lebanon, international interest in battlefield UAVs picked up significantly. During the 1980s, all the major military powers and many of the minor ones acquired a battlefield UAV capability, and continue to expand that capability. These battlefield UAVs fall into two broad categories, which can be designated for convenience as "combat surveillance" and "tactical reconnaissance" UAVs.
Combat surveillance UAV
The function of a combat surveillance UAV is to observe events on a battlefield in real-time, orbiting over the battle area and relaying intelligence to a ground control station. They are generally powered by small rotary or two-stroke piston "chain saw" engines.
They are directed by an autopilot system with RC backup. The autopilot directs the aircraft from sets of waypoints programmed in before takeoff. The flight-plan is set up by displaying a map on a workstation, clicking on the desired map coordinates with a mouse or directly on to a touch-screen, and then uploading the flight-plan into the UAV. Navigation is often verified by a GPS-INS navigation system. However, combat surveillance UAVs usually use the autopilot to get to the operating area, with the aircraft then operating by radio control to find targets of opportunity. The need to stay within radio range restricts combat surveillance UAVs to ranges within a line-of-sight of the transmitter. This is usually the determining factor in "range" specifications for such UAVs. For this reason, "endurance" is a more useful specification than "range".
The UAV sensors are generally housed in a turret underneath the aircraft, and almost always feature day-night imagers. The turret may also include a laser designator to allow the UAV to mark targets for smart weapons. Other specialized payloads, such as SIGINT packages, or new lightweight synthetic aperture radar (SAR)sensors with all-weather imaging capability, are now being fielded as well.
The larger combat surveillance UAVs have landing gear, usually fixed, and can take off and land on an unimproved airstrip, with an arresting hook to snag a cable for short landings. Such UAVs may also be launched by a RATO booster, and recovered by parachute, parasail, or by flying into a net. Smaller combat surveillance UAVs may be launched with a pneumatic, hydraulic, or electric catapult, with the very smallest launched by an elastic-bungee catapult.
Tactical reconnaissance UAV
The tactical reconnaissance UAV is usually larger, jet powered, with longer range and higher speed. Like a combat surveillance UAV, it has an autopilot with radio control backup, but it relies more on the autopilot than on radio control, since its primary mission is to fly over predesignated targets out of line of sight, take pictures, and then come home. The tactical reconnaissance UAV will usually not loiter over the battle area, and real-time intelligence is less essential.
A tactical reconnaissance UAV usually carries day-night reconnaissance cameras, rather than a sensor turret, though SAR can be carried as well. They are generally launched by RATO booster and recovered by parachute, though they can be launched from aircraft as well.
The dividing line between combat surveillance and tactical reconnaissance UAVs, as well as between them and other classes of UAVs, is fuzzy. Some types of UAV may be usable for both missions. The distinction between a combat surveillance UAV and some kinds of "endurance" UAVs, discussed later, and between a tactical reconnaissance and a strategic reconnaissance UAV, as discussed earlier, is also very thin.