A method of translating performance characteristics for a gas turbine engine from one engine condition to another engine condition, the method conducted continuously, and in real-time, while the engine is operating, the method comprising the steps of: sensing, at a current engine condition, a first engine performance parameter and a second engine performance parameter, the first and second engine performance parameters corresponding to a measured performance characteristic value of the engine; retrieving, from a memory, a first reference performance datum associated with the first and second engine performance parameters at the current engine condition; retrieving, from the memory, a second reference performance datum associated with the first and second engine performance parameters at a selected reference engine condition; calculating, in a processor, a difference between the first reference performance datum and the second reference performance datum, to thereby generate a translation value (Vtranslate); translating, in the processor, the measured performance characteristic value of the engine by an amount equal to the translation value, to thereby generate a corrected performance characteristic value of the engine at the selected reference engine condition; for the corrected performance characteristic value, calculating by the processor, an estimate of the first engine performance parameter at a predetermined value of the second engine performance parameter using two previously stored performance characteristic curves representative of the steady state relationship between the first and second engine performance parameters; filtering by the processor, the calculated estimate of the first engine performance parameter to generate a filtered first parameter estimate value; and using the filtered first parameter estimate value to supply by the processor, estimates, to a user, of power available from the engine, wherein: the first engine performance parameter is power turbine inlet temperature; the second engine performance parameter is engine torque (Qc); the predetermined value of the second engine performance parameter is maximum rated power torque; and the calculated estimate of the first engine performance parameter is a calculated estimate of power turbine inlet temperature at the maximum rated power torque. sensing, at a current engine condition, a first engine performance parameter and a second engine performance parameter, the first and second engine performance parameters corresponding to a measured performance characteristic value of the engine; retrieving, from a memory, a first reference performance datum associated with the first and second engine performance parameters at the current engine condition; retrieving, from the memory, a second reference performance datum associated with the first and second engine performance parameters at a selected reference engine condition; calculating, in a processor, a difference between the first reference performance datum and the second reference performance datum, to thereby generate a translation value (Vtranslate); translating, in the processor, the measured performance characteristic value of the engine by an amount equal to the translation value, to thereby generate a corrected performance characteristic value of the engine at the selected reference engine condition; for the corrected performance characteristic value, calculating by the processor, an estimate of the first engine performance parameter at a predetermined value of the second engine performance parameter using two previously stored performance characteristic curves representative of the steady state relationship between the first and second engine performance parameters; filtering by the processor, the calculated estimate of the first engine performance parameter to generate a filtered first parameter estimate value; and using the filtered first parameter estimate value to supply by the processor, estimates, to a user, of power available from the engine, wherein: the first engine performance parameter is power turbine inlet temperature; the second engine performance parameter is engine torque (Qc); the predetermined value of the second engine performance parameter is maximum rated power torque; and the calculated estimate of the first engine performance parameter is a calculated estimate of power turbine inlet temperature at the maximum rated power torque. the first engine performance parameter is power turbine inlet temperature; the second engine performance parameter is engine torque (Qc); the predetermined value of the second engine performance parameter is maximum rated power torque; and the calculated estimate of the first engine performance parameter is a calculated estimate of power turbine inlet temperature at the maximum rated power torque.