A method of deicing a plurality of propeller blades (20, 22, 24, 26) on an aircraft, the method comprising: determining an ambient temperature; determining an airspeed of the aircraft; calculating a heater on time as a function of the ambient temperature and the airspeed; and powering a heater for one or more blades (20, 22, 24, 26) in the plurality of blades for the heater on time, characterised in that: powering a heater comprises powering the heater for a set of two or more opposing blades in the plurality of blades (20, 22, 24, 26) for the heater on time; calculating the heater on time comprises: calculating, for the ambient temperature and the airspeed determined, a plurality of blade surface temperatures over a period of time with the heater on at a first time and the heater off when the surface temperature of the blade reaches approximately 32° Fahrenheit (0° Celsius); and determining the heater on time from the calculated blade surface temperatures; and wherein a heater off time is equal to the heater on time multiplied by the number of sets of blades in the plurality of blades (20, 22, 24, 26) minus one, and wherein determining the heater on time comprises calculating, for the calculated blade surface temperatures, a minimum heating cycle blade surface temperature from which the blade will heat to approximately 32° Fahrenheit (0° Celsius) in an optimum heater on time and to which the blade will cool from approximately 32° Fahrenheit (0° Celsius) in an optimum heater off time that is equal to the optimum heater on time multiplied by the number of sets of blades in the plurality of blades minus one. determining an ambient temperature; determining an airspeed of the aircraft; calculating a heater on time as a function of the ambient temperature and the airspeed; and powering a heater for one or more blades (20, 22, 24, 26) in the plurality of blades for the heater on time, characterised in that: powering a heater comprises powering the heater for a set of two or more opposing blades in the plurality of blades (20, 22, 24, 26) for the heater on time; calculating the heater on time comprises: calculating, for the ambient temperature and the airspeed determined, a plurality of blade surface temperatures over a period of time with the heater on at a first time and the heater off when the surface temperature of the blade reaches approximately 32° Fahrenheit (0° Celsius); and determining the heater on time from the calculated blade surface temperatures; and wherein a heater off time is equal to the heater on time multiplied by the number of sets of blades in the plurality of blades (20, 22, 24, 26) minus one, and wherein determining the heater on time comprises calculating, for the calculated blade surface temperatures, a minimum heating cycle blade surface temperature from which the blade will heat to approximately 32° Fahrenheit (0° Celsius) in an optimum heater on time and to which the blade will cool from approximately 32° Fahrenheit (0° Celsius) in an optimum heater off time that is equal to the optimum heater on time multiplied by the number of sets of blades in the plurality of blades minus one. powering a heater comprises powering the heater for a set of two or more opposing blades in the plurality of blades (20, 22, 24, 26) for the heater on time; calculating the heater on time comprises: calculating, for the ambient temperature and the airspeed determined, a plurality of blade surface temperatures over a period of time with the heater on at a first time and the heater off when the surface temperature of the blade reaches approximately 32° Fahrenheit (0° Celsius); and determining the heater on time from the calculated blade surface temperatures; and wherein a heater off time is equal to the heater on time multiplied by the number of sets of blades in the plurality of blades (20, 22, 24, 26) minus one, and wherein determining the heater on time comprises calculating, for the calculated blade surface temperatures, a minimum heating cycle blade surface temperature from which the blade will heat to approximately 32° Fahrenheit (0° Celsius) in an optimum heater on time and to which the blade will cool from approximately 32° Fahrenheit (0° Celsius) in an optimum heater off time that is equal to the optimum heater on time multiplied by the number of sets of blades in the plurality of blades minus one. calculating, for the ambient temperature and the airspeed determined, a plurality of blade surface temperatures over a period of time with the heater on at a first time and the heater off when the surface temperature of the blade reaches approximately 32° Fahrenheit (0° Celsius); and determining the heater on time from the calculated blade surface temperatures; and wherein a heater off time is equal to the heater on time multiplied by the number of sets of blades in the plurality of blades (20, 22, 24, 26) minus one, and wherein determining the heater on time comprises calculating, for the calculated blade surface temperatures, a minimum heating cycle blade surface temperature from which the blade will heat to approximately 32° Fahrenheit (0° Celsius) in an optimum heater on time and to which the blade will cool from approximately 32° Fahrenheit (0° Celsius) in an optimum heater off time that is equal to the optimum heater on time multiplied by the number of sets of blades in the plurality of blades minus one.