A method includes detecting at least one position measurement of a separator piston of a pitch trim actuator. The method includes detecting at least one pressure measurement of a gas. The method includes detecting at least one temperature measurement of the gas. The method includes storing at least one position value based on the at least one position measurement of the separator piston, at least one pressure value based on the at least one pressure measurement of the gas and at least one temperature value based on the at least one temperature measurement of the gas. The method includes determining a volume of an oil within an oil chamber of the pitch trim actuator and a pressure of the gas within the gas chamber of the pitch trim actuator, based on the at least one position value, the at least one pressure value and the at least one temperature value.