A compound helicopter that extends in a longitudinal direction, a transversal direction, and a vertical direction, comprising: a fuselage that extends in the longitudinal direction from a front fuselage section to a rear fuselage section, and in the vertical direction from a lower fuselage section to an upper fuselage section; at least one main rotor that is arranged at the upper fuselage section and at least adapted for generating lift in operation, the at least one main rotor comprising: at least two rotor blades (2a, 2b) that form a main rotor disc during rotation of the at least one main rotor, wherein the main rotor disc defines a compound helicopter perimeter; and a fixed wing arrangement that is completely arranged within the compound helicopter perimeter and laterally arranged relative to the fuselage, the fixed wing arrangement comprising: a rear horizontal plane structure that extends laterally from the rear fuselage section in the transversal direction, at least one vertical fin that is arranged with a predetermined angle at the rear horizontal plane structure, at least one upper wing that is connected to the upper fuselage section, at least one lower wing that is connected to the lower fuselage section and comprises an outboard section and an inboard section, wherein the inboard section is connected to the fuselage and integrally formed with the rear horizontal plane structure, and wherein the outboard section is connected to the inboard section at a lower wing joint area, and an interconnection region, in which one of the at least one upper wing is connected to an associated one of the at least one lower wing. a fuselage that extends in the longitudinal direction from a front fuselage section to a rear fuselage section, and in the vertical direction from a lower fuselage section to an upper fuselage section; at least one main rotor that is arranged at the upper fuselage section and at least adapted for generating lift in operation, the at least one main rotor comprising: at least two rotor blades (2a, 2b) that form a main rotor disc during rotation of the at least one main rotor, wherein the main rotor disc defines a compound helicopter perimeter; and a fixed wing arrangement that is completely arranged within the compound helicopter perimeter and laterally arranged relative to the fuselage, the fixed wing arrangement comprising: a rear horizontal plane structure that extends laterally from the rear fuselage section in the transversal direction, at least one vertical fin that is arranged with a predetermined angle at the rear horizontal plane structure, at least one upper wing that is connected to the upper fuselage section, at least one lower wing that is connected to the lower fuselage section and comprises an outboard section and an inboard section, wherein the inboard section is connected to the fuselage and integrally formed with the rear horizontal plane structure, and wherein the outboard section is connected to the inboard section at a lower wing joint area, and an interconnection region, in which one of the at least one upper wing is connected to an associated one of the at least one lower wing. a rear horizontal plane structure that extends laterally from the rear fuselage section in the transversal direction, at least one vertical fin that is arranged with a predetermined angle at the rear horizontal plane structure, at least one upper wing that is connected to the upper fuselage section, at least one lower wing that is connected to the lower fuselage section and comprises an outboard section and an inboard section, wherein the inboard section is connected to the fuselage and integrally formed with the rear horizontal plane structure, and wherein the outboard section is connected to the inboard section at a lower wing joint area, and an interconnection region, in which one of the at least one upper wing is connected to an associated one of the at least one lower wing.