Method and device for vertical guidance of an aircraft

A method for guiding an aircraft (A) in a vertical plane in order to join and follow a prescribed flight path (T) which is defined in said vertical plane and is formed by successive straight segments (S1, S2), wherein the following operations are performed repeatedly:

• the straight segment (S1) which belongs to said flight path (T) and relative to which said aircraft (A) is to be guided, is determined;
• the vertical distance he, between said aircraft (A) and the guidance segment (S1) thus determined, is determined;
• the velocity difference ve between the actual vertical velocity (Vz) of the aircraft (A) and the vertical velocity (Vzth) which it would have if it moved along said guidance segment (S1), for an equal velocity parallel to the ground, is determined;
• a vertical acceleration variation .DELTA.nz is calculated from the equation:
• .DELTA.nz=((k1.(he-hc))+(ve-vc)).k2
• in which:
• k1 and k2 represent characteristic coefficients,
• hc and vc represent precontrol terms, of nonzero values when the aircraft is in flight path joining status, and of zero values when the aircraft is in flight path following status, and
• the product k1.(he-hc) is restricted between two predefined values;
• and
• the vertical acceleration variation Anz thus calculated and restricted between two predefined values is applied as control input to the aircraft (A).