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.roneverhart.com/HGST-Ultrastar-7K6000-HUS726040ALS214-4TB-7-2K-RPM-SAS-12Gb-s-512n-128MB-3-5-SE-Hard-Drive/