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System and method for improving transition lift-fan performance

  • US 10,427,784 B2
  • Filed: 12/05/2011
  • Issued: 10/01/2019
  • Est. Priority Date: 12/05/2011
  • Status: Active Grant
First Claim
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1. A vertical takeoff and landing (VTOL) aircraft having reduced peak power requirements during a transition flight between a hovering flight and a wingborne forward flight, the VTOL aircraft comprising:

  • a wing to provide lift during the wingborne forward flight and to provide an increasing amount of lift as airspeed increases during the transition flight;

    a fuselage coupled with the wing, the fuselage being positioned to define a first wing portion on a first side of the fuselage and a second wing portion on a second side of the fuselage that is opposite that of the first side, wherein the first and second wing portions are substantially equal in length;

    a forward thrust propulsion system coupled to said fuselage to produce a desired horizontal thrust during said wingborne forward flight and to accelerate the VTOL aircraft forward during said transition flight;

    a first plurality of ducted lift fans positioned on the first wing portion to generate, in aggregate, a first desired total vertical thrust during said hovering flight, each of said first plurality of ducted lift fans having an axis of rotation that is fixed and substantially vertical, each of said first plurality of ducted lift fans being configured to be independently controlled between three throttle states, the three throttle states including a substantially full throttle state, an intermediate throttle state, and a substantially zero throttle state;

    a second plurality of ducted lift fans positioned on the second wing portion to generate, in aggregate, a second desired total vertical thrust during said hovering flight, each of said second plurality of ducted lift fans having an axis of rotation that is fixed and substantially vertical, each of said second plurality of ducted lift fans being configured to be independently controlled between the three throttle states,wherein, during said hovering flight and said transition flight, the VTOL aircraft is configured to independently control each of said first and second plurality of ducted lift fans,wherein, during said transition flight from said hovering flight, the VTOL aircraft is configured to switch a throttle state of (1) at least one of said first plurality of ducted lift fans to generate a third desired total vertical thrust as a function of momentum drag upon the VTOL aircraft, and (2) at least one of said second plurality of ducted lift fans to generate a fourth desired total vertical thrust as a function of the momentum drag, andwherein a number of ducted lift fans is maintained at the intermediate throttle state in each of said first and second plurality of ducted lift fans during said transition flight from said hovering flight is less than, or equal to, the sum of the ducted lift fans of each respective plurality of ducted lift fans operated in the substantially full throttle state and the substantially zero throttle state.

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