A rotary aircraft (1;1001;1101), comprising: a fuselage; a main rotor; a tail boom (3, 301;701;1201) attached to and extending from the fuselage, the tail boom having: a first surface and a second surface; a leading edge; a trailing edge, having: a rounded corner having a radius; wherein both the first surface and the second surface extend from the leading edge to the trailing edge; wherein the rounded corner joins the second surface to the trailing edge; and a tail rotor (4;319) attached to the tail boom (3; 301;701;1201); wherein the tail boom creates a high-pressure region about the first surface and a low-pressure region about the second surface in the downward rotorwash flowing therearound, which in turn creates a lateral force in a direction opposing a fuselage torque during flight; characterized in that: the tail boom further comprises a sharp edge wherein the sharp edge: - has an angle of about 90 degrees; - joins the first surface to the trailing edge at about the 90 degree angle and - reduces drag of the tail boom (3; 301; 701; 1201) during a sideward flight motion of the aircraft (1;1001; 1101) in a direction from the first to the second surface. a fuselage; a main rotor; a tail boom (3, 301;701;1201) attached to and extending from the fuselage, the tail boom having: a first surface and a second surface; a leading edge; a trailing edge, having: a rounded corner having a radius; wherein both the first surface and the second surface extend from the leading edge to the trailing edge; wherein the rounded corner joins the second surface to the trailing edge; and a tail rotor (4;319) attached to the tail boom (3; 301;701;1201); wherein the tail boom creates a high-pressure region about the first surface and a low-pressure region about the second surface in the downward rotorwash flowing therearound, which in turn creates a lateral force in a direction opposing a fuselage torque during flight; characterized in that: the tail boom further comprises a sharp edge wherein the sharp edge: - has an angle of about 90 degrees; - joins the first surface to the trailing edge at about the 90 degree angle and - reduces drag of the tail boom (3; 301; 701; 1201) during a sideward flight motion of the aircraft (1;1001; 1101) in a direction from the first to the second surface. a first surface and a second surface; a leading edge; a trailing edge, having: a rounded corner having a radius; a rounded corner having a radius; wherein both the first surface and the second surface extend from the leading edge to the trailing edge; wherein the rounded corner joins the second surface to the trailing edge; and a tail rotor (4;319) attached to the tail boom (3; 301;701;1201); wherein the tail boom creates a high-pressure region about the first surface and a low-pressure region about the second surface in the downward rotorwash flowing therearound, which in turn creates a lateral force in a direction opposing a fuselage torque during flight; characterized in that: - has an angle of about 90 degrees; - joins the first surface to the trailing edge at about the 90 degree angle and - reduces drag of the tail boom (3; 301; 701; 1201) during a sideward flight motion of the aircraft (1;1001; 1101) in a direction from the first to the second surface.