Patent ID: 7571878

Claim:
A ground collision calculating unit configured to calculate a recovery flight path for an aircraft in order to avoid a collision with ground, the ground collision calculating unit comprising: a receiving circuit configured to receive signals comprising information of a dive angle of the aircraft, and a present roll angle of the aircraft, and a path calculating circuit configured to calculate a recovery flight path that avoids collision with the ground on the basis of said information, the path calculating circuit comprising a first calculating module configured to calculate a need for rolling the aircraft based on the present roll angle, and a second calculating module configured to calculate a need for changing the direction of a velocity vector of the aircraft so that the calculated change has a component in an upward direction in relation to a reference frame of the aircraft, wherein the first calculating module is further configured to calculate the need for rolling the aircraft based on the dive angle so that the calculated flight path turns sideways when the dive angle surpasses a specified dive angle and when the present roll angle is larger than zero degrees, and so that the flight path continues in a forward direction when the dive angle is below said specified dive angle.