Abstract: A computer system 20 provided in an aircraft 1 includes, as a module of a computer program to be executed, an approach determination section 31 configured to determine whether the aircraft 1 is approaching a landing site. The approach determination section 31 includes, as a condition for determination of approaching, establishment (C1) of one or both of a condition (C11) that a first absolute altitude A1 obtained by an radio altimeter 21 mounted on the aircraft 1 is low relative to a first approach altitude AA1, and a condition (C12) that a second absolute altitude A2 that is obtained by subtracting an altitude AL of the landing site from a pressure altitude Ap determined by a barometric altimeter 22 mounted on the aircraft 1 is low relative to a predetermined second approach altitude AA2.

Abstract: A computer system 20 provided in an aircraft 1 includes, as a module of a computer program to be executed, an approach determination section 31 configured to determine whether the aircraft 1 is approaching a landing site. The approach determination section 31 includes, as a condition for determination of approaching, establishment (C1) of one or both of a condition (C11) that a first absolute altitude A1 obtained by an radio altimeter 21 mounted on the aircraft 1 is low relative to a first approach altitude AA1, and a condition (C12) that a second absolute altitude A2 that is obtained by subtracting an altitude AL of the landing site from a pressure altitude Ap determined by a barometric altimeter 22 mounted on the aircraft 1 is low relative to a predetermined second approach altitude AA2.