For developers of unmanned aerial vehicles (UAVs), combining sufficient speed, a high payload, maneuverability, low fuel consumption, high endurance and minimum takeoff and landing distances is a dream scenario. Italian company Nimbus is trying to make this proposition a reality with its Metaplane.
At its base in Lombardore, close to Turin, the company started flight tests of the preproduction version of the Metaplane in May 2006, having flown prototypes for the previous three years. Its conceivers intend to combine the positive aspects of airplanes and airships.
The Metaplanes are made of a hard structure, which carries the horizontal and vertical stabilizers, the engine and ancillary equipment, as well as the payload. Its “wing” is an aerodynamic helium-inflated structure that provides static lift to allow very low takeoff and landing speeds with very short runs. During flight, the wing generates aerodynamic lift.
The wing’s delta shape ensures maximum efficiency at low incidence, while at high incidence (up to 40 to 50 degrees), the Metaplane does not stall and will hover thanks to the combination of limited dynamic lift, static lift and propeller thrust. The aircraft architecture provides, moreover, an intrinsic stability on the roll axis.
Another major advantage of Nimbus’ design is the high payload versus maximum takeoff weight obtained combining static and dynamic lift. Two different Metaplanes have been developed–NBS20 and NBS35. The numbers indicate maximum takeoff weight (in kilograms) with 9- and 15-kg payloads (for sensors and fuel, respectively), around 20 and 33 pounds, representing more than 40 percent of the overall weight.
Both aircraft have the same wingspan–just under 20 feet–although the wing shape and volumes are different. Their speeds are also similar, varying between 10 and 25 knots. The service ceiling varies considerably, at between 500 and 1,000 feet for the NBS20 and between 1,000 and 3,280 feet for the NBS35.
The endurance of the two Metaplane models also varies. For the NBS20 this is 2.5 hours with a 4-kg (8.8-pound) sensors payload, while the NBS35 can fly for more than six hours with a 6-kg (13.2-pound) payload. Both aircraft are powered by an eight-horsepower, two-cylinder engine that drives a two-blade ducted propeller.
The NBS35 has a longer takeoff and landing run than the NBS20. However, its impact on operations is limited as the larger aircraft needs less than 15 feet to take to the air, while the smaller requires about 12 feet.
The Metaplane’s flight control systems allow the pilot on the ground to execute the mission using a number of automatic features that allow the aircraft to stay on the correct path with minimum effort. The planned flight path is verified continuously by the UAV using GPS data, and the system corrects the deviation imposed by external forces such as wind gusts.
The secure datalink between the aircraft and the ground control station allows for transmission of data and imagery and employs an antenna system to reduce power consumption. A fail-safe mechanism takes control of the UAV in case of failures such as the lack of GPS signal, a sudden decrease in altitude, engine failure, electrical shutdown or the loss of communication between the aircraft and the ground control station.
Given their flight performance, the Metaplanes may answer many operational needs in the homeland security and civil fields. Other possible applications for the UAVs would include reconnaissance over powerlines and pipelines, monitoring major events and providing radio relay in case of emergency. Nimbus is already thinking about bigger models, and makes no secret of its dream eventually to produce future short-haul air transport platforms.
