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 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 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 . <EOS>