Tiltrotor UAV - The Bell Eagle Eye, Model 918
A tiltrotor aircraft uses tiltable (rotating) propellers, or proprotors, for lift and propulsion. For vertical flight the proprotors are angled to direct their thrust downwards, providing lift. In this mode of operation the craft is essentially identical to a helicopter. As the craft gains speed, the proprotors are slowly tilted forward, eventually becoming perpendicular to the ground. In this mode the wing provides the lift, and the wing's greater efficiency helps the tiltrotor achieve its high speed. In this mode, the craft is essentially a turboprop aircraft. Tiltrotors also provide substantially greater cruise altitude capability than helicopters. Tiltrotors can easily reach 20,000 ft or more whereas helicopters typically do not exceed 10,000 ft altitude. This feature will mean that some uses that have been commonly considered only for fixed-wing aircraft can now be supported with tiltrotors without need of a runway. A drawback however is that a tiltrotor suffers considerably reduced payload when taking off from high altitude.
Specifications
Capacity 200 lb (91 kg) payload
Length 18 ft 3 in (5.56 m)
Wingspan 24 ft 2 in (7.37 m)
Rotor diameter 10 ft 0 in (3.05 m)
Main rotor area 157 sq ft (14.6 sq m)
Height 6 ft 2 in (1.88 m)
Engine Pratt & Whitney PW200/55 Marine Turboprop, 641 shp (478 kW)
Maximum speed 225 mph (360 km/h) 200 knots.
Service ceiling 20,000 ft (6,096 m)
Endurance 6 hours