In this article. a fault tolerant controller (FTC) based on back-stepping sliding mode is proposed for a quadrotor unmanned aerial vehicle (UAV) with single-rotor failure. According to the working mechanism of the quadrotor. the control system of UAV is divided into position subsystem and attitude subsystem. https://www.bekindtopets.com/limited-price-U-S-WWII-M3-Submachine-Grease-Gun-Replica-All-Metal-great-offer/