Closed wing

Abstract: Windtunnel measurements of the flow around the tip tanks of a model of a Morane-Soulnier Paris aircraft have been used to design cambered and twisted auxiliary surfaces, each only 0.4% to 0.6% of the wing area, which unwound the tip vortices formed at incidence and in so doing experienced a thrust, effectively reducing the vortex drag. Flight tests on a Paris aircraft showed that three such sails per tip tank increased the effective aspect ratio of the wing by over 40%. The increase in the overall lift-drag ratio at a lift coefficient of 0.35 was 21% and the maximum lift-drag ratio increased from 12.5 to 15.8. More recent windtunnel tests have shown that sails have a similar effect when fitted to plain wing tips. The results suggest that three or four sails spiralled round the rear half of each wing tip will give best results. These encouraging results suggest that far more windtunnel, flight and design work should be done to realise the potential savings in drag and fuel. Starting in 1946 as the College of Aeronautics, the Cranfield Institute of Technology was granted university status in 1969. In 1993 it changed its name to Cranfield University.

Abstract: This report describes a study conducted in 2010 under the NASA Innovation Fund Award to develop innovative future air vehicle concepts. Aerodynamic optimization was performed to produce three different aircraft configuration concepts for low drag, namely drooped wing, inflected wing, and squashed fuselage. A novel wing shaping control concept is introduced. This concept describes a new capability of actively controlling wing shape in-flight to minimize drag. In addition, a novel flight control effector concept is developed to enable wing shaping control. This concept is called a variable camber continuous trailing edge flap that can reduce drag by as much as 50% over a conventional flap. In totality, the potential benefits of fuel savings offered by these concepts can be significant.

Abstract: Numerical methods for the design and analysis of arbitrary-planform wings at supersonic speeds are reviewed. Certain deficiencies are revealed, particularly in application to wings with slightly subsonic leading edges. Recently devised numerical techniques which overcome the major part of these deficiencies are presented. The original development as well as the more recent revisions are subjected to a thorough review.

Abstract: A tail sitter VTOL vehicle with two pairs of propellers mounted respectively on left wing, right wing, top and bottom vertical tail stabilizers. The wing propellers and tail propellers spin in opposite directions. Full attitude control is realized in all flight phases through differential powering of the four propellers coordinated by electronic control system. Four propellers together generate sufficient thrust to counter gravity in hover mode, while the wings provide aerodynamic lift for efficient forward flight.