A rotary-wing air vehicle comprising a main body (12) and at least two rotor devices (16a, 16b) arranged and configured to generate propulsion and thrust, in use, to lift and propel said air vehicle, said rotor devices (16a, 16b) being arranged and configured relative to said main body (12) such that the blades thereof do not cross through a central vertical axis of said main body (12) defining the centre of mass thereof, wherein said main body (12) is provided with an aperture (100) that extends therethrough to define a channel about said central vertical axis.