Patent ID: 8511602

Claim:
A ducted fan air-vehicle comprising: an air duct; a fan located within the air duct; a center body attached to the air duct and the fan; a plurality of groups of adjacent control vanes located within or downstream from the air duct, each group comprises at least two vanes; and a control device configured to control each vane, wherein the vanes of at least one of the groups of adjacent control vanes are deflected in the same direction, a first vane of the group deflected at a first angle of attack (AOA) and a second vane of the pair deflected at a second AOA different from the first AOA and exceeding a tandem threshold angle; wherein the first AOA is selected to allow the second AOA to exceed the tandem threshold angle without generating a stall condition; wherein the tandem threshold angle is an angle at which a stall condition occurs if exceeded by all vanes of a group operating at approximately a same AOA.