Warplanes: UAVs That Hover


May 26,2008: For the last eight years, the U.S. Department of Defense has been developing a helicopter UAV designed to stay in the air for over twelve hours at a time. The most recent test had this A160T Hummingbird staying in the air for 18.7 hours, at altitudes up to 15,000 feet, while carrying a 300 pound load (to simulate a typical sensor package). This set a record for unmanned UAVs weighing between half a ton and 2.5 tons. When the A160T landed, it still had 90 minutes worth of fuel left. The first flight test of the Hummingbird Unmanned Aerial Vehicle took place six years ago.

The A160T is a small helicopter, 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 A160T uses a commercial 300 horsepower automobile engine. This enables better control over speed, since turbines must run at nearly the same speed all the time. A piston engine can idle at 50 percent power. That control made the UAV better at what helicopters do best, just stay in one place. But in addition, that long endurance was to translate into 4,500 kilometers range. After the first flight test, it was believed the aircraft might be ready for production by 2006. That was too optimistic. Helicopters are complex beasts, and things take longer.

Currently, a production decision is not expected for another year. If the Hummingbird does get into production, it will make a very useful UAV for stakeouts, watching for the enemy to make a move. The Hummingbird will also be armed, and one has been configured with stubby wings, capable of carrying eight (hundred pounds each) Hellfire missiles. The U.S. Navy is interested in the A160, because it can operate off any ship with a helipad.

The A160 has some competition in the RQ-8B Fire Scout, which can stay in the air for up to eight hours at a time (five hour missions are more common), 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-8A is being developed for use on smaller navy ships, as well as with army combat units.

The U.S. Army version of the RQ-8A will be particularly useful supporting combat operations in urban areas. Both the RQ-8A and the A160T carry day and night cameras, GPS and targeting gear (laser range finders and designators). 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. With its rotors folded (for storage on ships), the RQ-8 is 23 feet long and 9.4 feet high. Max payload is 600 pounds, meaning it would probably carry hundred pound Hellfire, or 44 pound Viper Strike missiles. 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 A160T is expected to have similar features, but cost at least 20 percent more.




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