Under the Hood

The Predator UAV is a medium-altitude, long-range aircraft that operates much like any other small plane.

Photo courtesy U.S. Air Force An airman works on the Predator's Rotax 914 engine.

A Rotax 914, four-cylinder, four-stroke, 101-horsepower engine, the same engine type commonly used on snowmobiles, turns the main drive shaft. The drive shaft rotates the Predator's two-blade, variable-pitch pusher propeller. The rear-mounted propeller provides both drive and lift. The remote pilot can alter the pitch of the blades to increase or decrease the altitude of the plane and reach speeds of up to 135 mph (120 kts). There is additional lift provided by the aircraft's 48.7-foot (14.8-meter) wingspan, allowing the Predator to reach altitudes of up to 25,000 feet (7,620 meters). The slender fuselage and inverted-V tails help the aircraft with stability, and a single rudder housed beneath the propeller steers the craft.

The fuselage of the Predator is a mixture of carbon and quartz fibers blended in a composite with Kevlar. Underneath the fuselage, the airframe is supported by a Nomex, foam and wood laminate that is pressed together in layers. Between each layer of laminate, a sturdy fabric is sandwiched in to provide insulation to internal components. The rib work of the structure is built from a carbon/glass fiber tape and aluminum. The sensor housing and wheels are also aluminum.

The edges of the wings are titanium and are dotted with microscopic weeping holes that allow an ethylene glycol solution to seep out of internal reservoirs and breakdown ice that forms on the wings during flight.

The Predator UAV uses run-of-the-mill mechanical systems. A 3-kilowatt starter/alternator supplies the craft's electronics with power; this is supplemented with auxiliary battery power. Forward and aft fuel tanks house rubberized fuel bladders that are easy to fill through gas caps located at the top of the fuselage. An operator starts the engine by attaching the umbilical cord of a Starter/Ground Power Cart to the aircraft's starter-control connector, located in the ground panel on the outside of the plane. An operator stops the engine by hitting a kill switch just behind one of the wings on the side of the plane.

For the Engine The Predator's two fuel tanks combined carry up to 600 pounds of 95-octane to 100-octane reciprocating aircraft engine fuel. The Predator uses 7.6 liters of standard motor oil for lubrication. In addition to venting, conventional automotive antifreeze is used to cool the engine. Two 8-pound, 14-amp-hour Ni-Cad battery packs are housed in the fuselage for backup power in case the engine or alternator fails.