Method of calibrating a heater system

1. A system for calibrating a heater system for heating a surface of a structure, the system comprising:

the structure;

the heater system, including:

a heater element;

a temperature sensor proximate the heater element for outputting a signal indicative of the temperature of the heater element; and

a controller for controlling the supply of power to the heater element in dependence on the signal to maintain the temperature of the heater element at a first substantially constant temperature;

a reservoir for immersing the structure in a fluid for maintaining the surface of the structure at a second substantially constant temperature;

a power supply for supplying an amount of power to the heater element; and

a sensor for receiving the signal from the temperature sensor and determining a temperature at the temperature sensor, wherein the system is configured to calibrate the heater system by determining a setpoint temperature for controlling the heater element in dependence on the signal and the second substantially constant temperature.

2. A system according to claim 1 , wherein the heater system is an ice protection system.

3. A system according to claim 2 , wherein the ice protection system is an aircraft ice protection system.

4. A system according to claim 1 , wherein the controller has a defined setpoint temperature different to the determined setpoint temperature.

5. A system according to claim 4 , further comprising a resistor in series or parallel with at least one of the heater element and the electrical properties of at least one of the respective heater element and the temperature sensor to cause the determined setpoint temperature to become substantially equal to the defined setpoint temperature.

6. A system according to claim 1 , wherein the structure is immersed in a thermal reservoir.

7. A system according to claim 6 , wherein the thermal reservoir is an ice bath.