A gas turbine engine comprising: a core that includes a turbine shaft configured to rotate about an engine axis; a tower shaft coupled to the turbine shaft; and a gearbox that includes: a housing that includes a cavity provided between opposing first and second mounting surfaces (76, 78); an input gear shaft coupled to the tower shaft; a drive gear (96; 98; 100) coupled to the input gear shaft and connected to first and second shaft portions (114, 116) that respectively extend to the first and second mounting surfaces (76, 78), the drive gear (96; 98; 100) configured to rotate about a gear axis; first and second accessory drive components respectively mounted to the first and second mounting surfaces (76, 78) and respectively coupled to the first and second shaft portions (114, 116); and a gear train having multiple drive gears (96; 98; 100) that includes the drive gear, each of the multiple drive gears (96; 98; 100) configured to rotate about a respective gear axis and having first and second shaft portions (114, 116) coaxial with one another and their respective drive gear (96; 98; 100), wherein the multiple drive gears (96; 98; 100) include first, second and third drive gears (96; 98; 100), and the first drive gear corresponds to the drive gear, characterised in that: the gearbox is mounted to the core; the gear axes of the multiple drive gears (96; 98; 100) are in a perpendicular orientation to the engine axis; and the gearbox is oriented longitudinally in the direction of the engine axis. a core that includes a turbine shaft configured to rotate about an engine axis; a tower shaft coupled to the turbine shaft; and a gearbox that includes: a housing that includes a cavity provided between opposing first and second mounting surfaces (76, 78); an input gear shaft coupled to the tower shaft; a drive gear (96; 98; 100) coupled to the input gear shaft and connected to first and second shaft portions (114, 116) that respectively extend to the first and second mounting surfaces (76, 78), the drive gear (96; 98; 100) configured to rotate about a gear axis; first and second accessory drive components respectively mounted to the first and second mounting surfaces (76, 78) and respectively coupled to the first and second shaft portions (114, 116); and a gear train having multiple drive gears (96; 98; 100) that includes the drive gear, each of the multiple drive gears (96; 98; 100) configured to rotate about a respective gear axis and having first and second shaft portions (114, 116) coaxial with one another and their respective drive gear (96; 98; 100), wherein the multiple drive gears (96; 98; 100) include first, second and third drive gears (96; 98; 100), and the first drive gear corresponds to the drive gear, a housing that includes a cavity provided between opposing first and second mounting surfaces (76, 78); an input gear shaft coupled to the tower shaft; a drive gear (96; 98; 100) coupled to the input gear shaft and connected to first and second shaft portions (114, 116) that respectively extend to the first and second mounting surfaces (76, 78), the drive gear (96; 98; 100) configured to rotate about a gear axis; first and second accessory drive components respectively mounted to the first and second mounting surfaces (76, 78) and respectively coupled to the first and second shaft portions (114, 116); and a gear train having multiple drive gears (96; 98; 100) that includes the drive gear, each of the multiple drive gears (96; 98; 100) configured to rotate about a respective gear axis and having first and second shaft portions (114, 116) coaxial with one another and their respective drive gear (96; 98; 100), wherein the multiple drive gears (96; 98; 100) include first, second and third drive gears (96; 98; 100), and the first drive gear corresponds to the drive gear, characterised in that: the gearbox is mounted to the core; the gear axes of the multiple drive gears (96; 98; 100) are in a perpendicular orientation to the engine axis; and the gearbox is oriented longitudinally in the direction of the engine axis. the gearbox is mounted to the core; the gear axes of the multiple drive gears (96; 98; 100) are in a perpendicular orientation to the engine axis; and the gearbox is oriented longitudinally in the direction of the engine axis.