Aerodynamic Characteristics of a 4-foot-diameter Ducted Fan Mounted on the Tip of a Semispan Wing

Aerodynamic Characteristics of a 4-foot-diameter Ducted Fan Mounted on the Tip of a Semispan Wing PDF

Author: Kenneth W. Mort

Publisher:

Published: 1962

Total Pages: 38

ISBN-13:

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Power, free-stream velocity, and duct angle of attack were varied at several wing angles of attack to define the aerodynamic characteristics of the ducted fan, wing, and of the ducted fan wing together. At large duct angles of attack, the inside of the upstream duct lip stalled causing a rapid change in the duct pitching moments and an accompanying increase in the power required. At low horizontal velocities, this lip stall would probably limit the rate of descent of a vehicle with a wing-tip-mounted ducted fan. During low-speed, level, unaccelerated flight (30 to 80 knots) it appeared that a vehicle, with a configuration similar to that examined, would require less power if it were supported by a wing and ducted fans than if it were supported only by ducted fans. (Author).

Aerodynamic Characteristics of a Powered Semispan Tilting-shrouded-propeller VTOL Model in Hovering and Transition Flight

Aerodynamic Characteristics of a Powered Semispan Tilting-shrouded-propeller VTOL Model in Hovering and Transition Flight PDF

Author: Kenneth W. Goodson

Publisher:

Published: 1962

Total Pages: 52

ISBN-13:

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"An investigation of the aerodynamic characteristics of a powered semispan tilting-shrouded-propeller configuration has been conducted in the 17-foot test section of the Langley 300-MPH 7- by 10-foot tunnel. The wing had an aspect ratio of 2.67 (based on wing span of 60 inches), a taper ratio of 0.67, and an NACA 2418 airfoil section with a 15-inch-diameter shrouded propeller mounted on the tip. The test results show that large nose-up pitching moments are obtained at transitional speeds of about 40 knots and duct angle of about 70°. Decelerating flight procedures further increases in the nose-up moment. Ground proximity reduces the nose-up pitching moments. The large nose-up moments can be trimmed by use of duct-exit control vanes. The results show that unloading the duct (shroud) by flying at a wing angle of attack of 15° reduces the power required by about 30 percent at 50 knots. Duct-lip stall produces large increases in power required. The results in general show that full-scale aerodynamic simulation can be made with small-scale wind-tunnel models if duct-lip separation at low Reynolds numbers is avoided."--Summary.

An Analytical Study of V/STOL Handling Qualities in Hover and Transition

An Analytical Study of V/STOL Handling Qualities in Hover and Transition PDF

Author: R. L. Stapleford

Publisher:

Published: 1965

Total Pages: 174

ISBN-13:

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The hover analysis considers pilot attitude and position control tasks in the presence of horizontal gusts. The effects of each of the stability derivatives on the difficulty of the control tasks and on the closed-loop gust responses are determined. It is clearly shown that the handling qualities studies of control sensitivity and angular damping must consider the influences of M sub u (or L sub v) and should include gust inputs. These conclusions are substantiated by previous variable-stability-helicopter experiments. The effects of vehicle size and geometry are investigated by several approaches. The key result of increasing size is found to be a reduction in M sub u and L sub v which can, in turn, lower the requirements for control power and damping. The handling qualities during transition of two vehicles, a tilt duct and a tilt wing, which were previously tested on a simulator are analyzed. It is shown that both trim control and perturbations about the trim conditions must be considered. In fact, part of the increased difficulty in landing transitions, in comparison with takeoff transitions, is due to more difficult trim control; the much more stringent position control requirements in landing are also a contributing factor.

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