Method of reducing a nose-up pitching moment on a ducted unmanned aerial vehicle

A method for restricting air flow into a duct of an unmanned aerial vehicle during forward flight, the unmanned aerial vehicle including counter-rotating rotor assemblies mounted within the duct, the duct extending downwardly through a fuselage in the unmanned aerial vehicle, each rotor assembly including a plurality of rotor blades, the method comprising the steps of:

• adjusting the rotor blades to have substantially zero pitch;
• rotating the rotor assemblies to produce a virtual plane across the duct, the virtual plane operative for substantially deflecting air passing over the fuselage away from the duct;
• and
• providing a plurality of pivotable deflectors on the bottom of the fuselage, the deflectors extending across the duct, the air flow across the bottom of the fuselage causing the deflectors to pivot and close off at least a portion of the bottom of the duct, thereby increasing the amount of air that passes under the fuselage, the increased air flow across the bottom of the fuselage generating a negative pressure aft of the duct on the top of the fuselage that creates a suction on the air passing over the duct.