translate English to French: (b) An operator must establish the mass and the centre of gravity of any aeroplane by actual weighing prior to initial entry into service and thereafter at intervals of 4 years if individual aeroplane masses are used and 9 years if fleet masses are used.
Les effets cumulés des modifications et des réparations sur la masse et le centrage doivent être pris en compte et dûment renseignés.