An unmanned aerial vehicle, UAV, comprising: an avionics system; a propulsion system; vertical-lift rotors; a controller; batteries configured to power the avionics system, the propulsion system, the vertical-lift rotors and the controller; and wings, wherein the controller comprises one or more processors configured to execute instructions stored in memory to perform operations comprising: in response to detecting loss of operation of the propulsion system, determining energy and time constraints based on (i) a remaining avionics battery life of the avionics system and (ii) a remaining rotor battery life of the vertical-lift rotors; using a rotor edgewise inflow model stored on the controller, evaluate parameters for a glide descent trajectory and subsequent rotor-powered flight trajectory to a candidate landing site, to determine whether, based on evaluation of the parameters, an estimated energy consumption during the rotor-powered flight trajectory and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, wherein: the glide descent trajectory comprises UAV operation using the avionics system, but without using the propulsion system and the vertical-lift rotors; and the rotor-powered flight trajectory comprises UAV operation using the vertical-lift rotors and the avionics system, but without using the propulsion system; and the operations further comprising: in response to determining that the estimated energy consumption and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, selecting an alternative candidate landing site. an avionics system; a propulsion system; vertical-lift rotors; a controller; batteries configured to power the avionics system, the propulsion system, the vertical-lift rotors and the controller; and wings, wherein the controller comprises one or more processors configured to execute instructions stored in memory to perform operations comprising: in response to detecting loss of operation of the propulsion system, determining energy and time constraints based on (i) a remaining avionics battery life of the avionics system and (ii) a remaining rotor battery life of the vertical-lift rotors; using a rotor edgewise inflow model stored on the controller, evaluate parameters for a glide descent trajectory and subsequent rotor-powered flight trajectory to a candidate landing site, to determine whether, based on evaluation of the parameters, an estimated energy consumption during the rotor-powered flight trajectory and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, wherein: the glide descent trajectory comprises UAV operation using the avionics system, but without using the propulsion system and the vertical-lift rotors; and the rotor-powered flight trajectory comprises UAV operation using the vertical-lift rotors and the avionics system, but without using the propulsion system; and the operations further comprising: in response to determining that the estimated energy consumption and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, selecting an alternative candidate landing site. in response to detecting loss of operation of the propulsion system, determining energy and time constraints based on (i) a remaining avionics battery life of the avionics system and (ii) a remaining rotor battery life of the vertical-lift rotors; using a rotor edgewise inflow model stored on the controller, evaluate parameters for a glide descent trajectory and subsequent rotor-powered flight trajectory to a candidate landing site, to determine whether, based on evaluation of the parameters, an estimated energy consumption during the rotor-powered flight trajectory and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, wherein: the glide descent trajectory comprises UAV operation using the avionics system, but without using the propulsion system and the vertical-lift rotors; and the rotor-powered flight trajectory comprises UAV operation using the vertical-lift rotors and the avionics system, but without using the propulsion system; and the operations further comprising: the glide descent trajectory comprises UAV operation using the avionics system, but without using the propulsion system and the vertical-lift rotors; and the rotor-powered flight trajectory comprises UAV operation using the vertical-lift rotors and the avionics system, but without using the propulsion system; and the operations further comprising: in response to determining that the estimated energy consumption and time needed for the UAV to land at the candidate landing site exceed the energy and time constraints, selecting an alternative candidate landing site.