A method of protecting an aircraft by automatically signaling against risks of collision with a terrain in a constrained environment when the aircraft follows a procedure with reduced protection corridor,
- said procedure defining a published trajectory to be followed by the aircraft along a predefined path located inside said reduced protection corridor, said published trajectory corresponding to an absolute geographical trajectory being published by authorized authorities and stored in an onboard database in the aircraft,
- said aircraft comprising an onboard Terrain Awareness and Warning System (TAWS) comprising a caution clearance sensor, said caution clearance sensor being a virtual surface calculated by an onboard computer delimiting an exploration volume of space in front of the aircraft that is compared to the topography of a corresponding terrain as supplied by an onboard terrain database, said caution clearance sensor having an origin corresponding to an extrapolated position of the aircraft few seconds to few tens of seconds ahead of a current position of the aircraft,
- said method comprising:
- adjusting via a computer position and orientation characteristics of said caution clearance sensor with respect to said published trajectory in order to match said reduced protection corridor,
- said position adjusting comprising relocating said origin of said caution clearance sensor at a new predicted position corresponding to an extrapolated position of the aircraft assuming the aircraft is following the published trajectory, said origin being thus situated inside limits of said reduced protection corridor,
- said orientation adjusting comprising orienting said caution clearance sensor to match said reduced protection corridor orientation taken at the relocated position,
- wherein
- if an estimated position of the aircraft presents a lateral deviation less than a first threshold relative to a prescribed trajectory, the position and orientation characteristics of the caution clearance sensor are adjusted so as to take into account direction characteristics of the published trajectory,
- if the estimated position of the aircraft presents a lateral deviation greater than a second threshold relative to the prescribed trajectory, the position and orientation characteristics of the caution clearance sensor continue to be determined by the TAWS operating conventionally, and
- if the estimated position of the aircraft presents a lateral deviation between the first and second thresholds relative to the prescribed trajectory, the position and orientation characteristics of the caution clearance sensor result from a combination between the adjustment as performed below the first threshold and the determination by the TAWS operating conventionally above the second threshold.