For the last decade, the U.S. Department of Defense has been developing helicopter UAVs, but so far, there has been little enthusiasm to buy a lot of them. The basic problem is that the ability hover, while useful, is not as important as being able to stay over an area for hours and hours, passing on video of what is going on down there. Fixed wing UAVs can do that more cheaply and reliably than can helicopter UAVs. That said, there are plenty of helicopter UAVs to come out of this decade of Department of Defense effort.
Most impressive is the RQ-8A Fire Scout, which is a helicopter type UAV that can stay in the air for up to eight hours at a time (five hour missions are more common). In addition to having an official RQ designation, the RQ-8A is being developed for use on smaller navy ships, as well as with army combat units. The U.S. Army version will be particularly useful supporting combat operations in urban areas. Both versions carry day and night cameras, GPS and targeting gear (laser range finders and designators). It has a top speed of 230 kilometers an hour, and can operate over 200 kilometers from its controller (on land, or a ship.) The RQ-8 is based on a two seat civilian helicopter (the Schweizer Model 333), and has a maximum takeoff weight of 1.5 tons. Each RQ-8 UAV costs about $8 million (including a share of the ground control equipment and some spares.) The flight control software enables the RQ-8 to land and take off automatically.
The slightly larger A160T is built for endurance. It is able to fly under remote control or under its own pre-programmed control. The two ton vehicle has a top speed of 255 kilometers an hour, and was originally designed to operate for up to 40 hours carrying a payload of 300 pounds. Maximum altitude was to be about 30,000 feet, and its advanced flight controls were to be capable of keeping it airborne in weather that would ground manned helicopters.
The U.S. Army has successfully tested a miniature helicopter UAV, called the MAV (Micro Air Vehicle), in Iraq. The 17 pound vehicle can fly as high as 500 feet, and carries day and night cameras. The MAV is most useful in urban environments, where it can quickly flit around buildings and other obstacles. The MAV has its blades contained within a cylindrical enclosure, and uses software control to keep it stable in flight. All the operator has to do is tell it where to go. Endurance, as with helicopters, depends on altitude. At sea level, the MAV will stay in the air for about 60 minutes, before it has to be refueled (it uses the same fuel as military vehicles.) But at 10,000 feet (typical in Afghanistan) it can stay in the air for only about 20 minutes. The MAV and control equipment can be carried in a special container which, when loaded weighs about 40 pounds. It can be backpacked. The MAV costs about $35,000.
The latest helicopter UAV is the Vigilante 502, which is a half ton aircraft based on a manned helicopter. It can carry 300 pounds, and has a cruising speed of 80 kilometers an hour (and a top speed of 171 kilometers an hour). This UAV can stay in the air for about six hours per sortie.
While these helicopter UAVs can carry weapons, this can be done more economically with fixed wing UAVs. Another problem with helicopter UAVs is greater vulnerability to ground fire when they hover. This is a problem with all helicopters, which are also more complex mechanically and more time consuming and expensive to maintain..