1. A method of configuring a software defined radio of an aircraft to implement a plurality of avionics functions, the software defined radio comprising configurable avionics function implementation circuitry, the method comprising: receiving, at a priority arbitrator of the software defined radio, an input indicating that a next phase of flight of the aircraft is imminent and that the software defined radio should be reconfigured; using the priority arbitrator to determine a full set of avionics functions for the next phase of flight; using the priority arbitrator to determine the availability of all required components of the configurable avionics function implementation circuitry needed to implement the full set of avionics functions for the next phase of flight and to identify components of the configurable avionics implementation circuitry which are unavailable, due to failure, to implement the full set of avionics functions for the next phase of flight such that the full set of avionics functions for the next phase of flight cannot be implemented by available components of the configurable avionics function implementation circuitry; upon identification of the components of the configurable avionics implementation circuitry which are unavailable, due to failure, to implement the full set of avionics functions for the next phase of flight, using the priority arbitrator to determine an alternate deterministic configuration which includes a subset of avionics functions which is less than the full set of avionics functions for the next phase of flight; and automatically loading into the configurable avionics function implementation circuitry the alternate deterministic configuration, which includes the subset of avionics functions which is less than the full set of avionics functions for the next phase of flight, to reconfigure the software defined radio.