Propulsion unit

Abstract

A turboprop propulsion unit for an aircraft comprises a propeller 22 which is driven by a core engine by means of a propeller turbine 26 which drives the propeller 22 through a shaft 28 and a propeller gearbox 24. Restarting of the engine in flight is achieved by windmilling of the propeller 22, which drives a propeller gearbox lubricant pump 30. A diverter valve 40 causes lubricant delivered by the propeller gearbox lubricant pump 30 to be supplied to a turbomachinery lubricant pump 18 along a restart conduit 44, so as to drive the turbomachinery lubricant pump 18 as a motor. Torque generated by the turbomachinery lubricant pump 18 is transferred through an accessory gearbox 12 to a spool 4, 6, 8 of the core engine 2 and to a fuel pump 16. Control of the pitch of blades 36 of the propeller 22 enables the windmilling propeller 22 to achieve a desired speed of the spool 4, 6, 8 and output of the fuel pump 16 sufficient to restart the engine 2, even at low air speeds.

Dependencies are inferred from the claim text.