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  • Old VTOL Ideas Never Die
    Posted by Graham Warwick 9:17 PM on Feb 15, 2010

    American Dynamics Flight Systems, a small US firm based in Maryland, is developing a VTOL unmanned aircraft with a mix of private equity and state funding in the hope of interesting the US Marine Corps in its design, the AD-150, for the planned Group 4 expeditionary UAS, formerly called VUAS.

    Video: American Dynamics Flight Systems

    AFDS makes no secret of the fact its design is not entirely new - the AD-150 is very similar in concept to the Doak VZ-4, the first tilt-duct VTOL aircraft, which first flew in February 1958 and completed more than 50 hours of flight testing.

    Video: Discovery Channel, via Wikipedia

    The two-seat VZ-4 had a gross weight of 3,200lb and an 860shp Lycoming YT53 turboshaft in the fuselage powering a pair of shaft-driven 48in-diameter propellers in tilting ducts on the wingtips. Variable inlet guide vanes in the ducts controlled propeller thrust for roll while vanes in the turboshaft exhaust provided pitch and yaw control in the hover and transition. Speed was 200kt.

    The unmanned AD-150 has a design gross weight of 2,350lb and a modern turboshaft, like the Pratt & Whitney Canada PW200, driving a pair of 38in-diameter fans inside 45in-diameter nacelles. Design speed is 300kt, with a 500lb payload. Low-speed pitch and yaw control is the same as in the VZ-4, but AFDS's patented "high-torque aerial lift" ducted fans can also independently tilt laterally to provide directional control.

    The company has so far windtunnel-tested the AD-150 airframe - without wingtip nacelles - at the University of Maryland and later this year will return to UMD to windtunnel-test the ducted fan. This will involve running a scaled, powered ducted fan at different tunnel speeds, fan velocities and duct angles representative of transition between vertical and horizontal flight - the key VTOL phase.

    AFDS is also building a full-scale "iron bird" ground rig to test the propulsion system. This will include the engine, transmission, drive train and ducted fans, laid out as if in the aircraft. The rig is scheduled to run before the end of the year. Ironically, the iron bird will use a Lycoming T53 turboshaft - the same type as flown in the Doak VZ-4.

    Tags: AWT, VTOL, VZ-4, UAV

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