Patent ID: 7283895

Claim:
A method of calculating at least one target speed for an aircraft, which is guided at said target speed along a flight plan that exhibits at least one time constraint constraining the aircraft to get to a particular flight point at a predetermined time, according to which method: a) determining the actual time at which the aircraft gets to said particular flight point, taking account of the current target speed; b) calculating a time interval corresponding to the difference between said predetermined time and said actual time; c) comparing said time interval with a duration of comparison which is variable and which depends on the actual distance between the current position of the aircraft and said particular flight point in such a way that said duration of comparison decreases at least in part when said actual distance decreases; and d) updating said target speed and applying the updated target speed to the aircraft, if said time interval is greater than said duration of comparison, wherein said actual distance between the current position of the aircraft and said particular flight point is determined, and wherein said duration of comparison varies as a function of said actual distance: along a first convergence curve, when the aircraft has to decelerate; and along a second convergence curve, when the aircraft has to accelerate, said first and second convergence curves being different and forming a cone of convergence which is asymmetric and which exhibits at least in part different values depending on whether the aircraft is late or early with respect to the time constraint, wherein: the asymmetric cone takes account of the different abilities of the aircraft to accelerate and decelerate.