Safety system seeking to avoid an accident during pilotage of a helicopter and to minimise the consequences of same when the accident of said helicopter is unavoidable, said safety system including: • a computer , which allows, at any instant t, an envelope of fallback trajectories of the helicopter to be generated in three dimensions, said envelope being obtained by calculating, at the instant t, a set of positions attainable by the helicopter during a predetermined duration of flight, said computer being parameterised beforehand with data relating to the flight capabilities of the helicopter including at least one of the following capabilities: maximum speeds and accelerations in the three directions of space, derived of higher order from at least one of the maximum speeds or accelerations in the three directions of space, minimum turning radii of the yawing movement, climb or descent angles, maximum weight of the payload and maximum stress values, • an emergency device allowing a warning signal to be emitted when the number of fallback trajectories is less than a first threshold value, said first threshold value being variable according to a speed of reduction of said number of fallback trajectories , the emergency device allowing the automatic transmission of flight data to rescue authorities, said flight data being chosen among the group including the coordinates of latitude and longitude provided by a GPS module, the speed and direction of flight, and • a control device , which allows, when the number of fallback trajectories is zero, corrective pilotage actions of the helicopter to be implemented so as to minimise the consequences of the accident of the helicopter . • a computer , which allows, at any instant t, an envelope of fallback trajectories of the helicopter to be generated in three dimensions, said envelope being obtained by calculating, at the instant t, a set of positions attainable by the helicopter during a predetermined duration of flight, said computer being parameterised beforehand with data relating to the flight capabilities of the helicopter including at least one of the following capabilities: maximum speeds and accelerations in the three directions of space, derived of higher order from at least one of the maximum speeds or accelerations in the three directions of space, minimum turning radii of the yawing movement, climb or descent angles, maximum weight of the payload and maximum stress values, • an emergency device allowing a warning signal to be emitted when the number of fallback trajectories is less than a first threshold value, said first threshold value being variable according to a speed of reduction of said number of fallback trajectories , the emergency device allowing the automatic transmission of flight data to rescue authorities, said flight data being chosen among the group including the coordinates of latitude and longitude provided by a GPS module, the speed and direction of flight, and • a control device , which allows, when the number of fallback trajectories is zero, corrective pilotage actions of the helicopter to be implemented so as to minimise the consequences of the accident of the helicopter . <EOS>