초록 ▼

The present invention relates to a method and to an instrument for determining the limiting margin of a surveillance parameter of a turboshaft engine. During a preliminary stage, a secondary processor means (11) determines a preliminary comfort margin. Thereafter, during a main stage, it estimates a

The present invention relates to a method and to an instrument for determining the limiting margin of a surveillance parameter of a turboshaft engine. During a preliminary stage, a secondary processor means (11) determines a preliminary comfort margin. Thereafter, during a main stage, it estimates a useful comfort margin from the preliminary comfort margin, and then an apparent difference between the current value and the limit value of the surveillance parameter, and finally the limiting margin by subtracting the useful comfort margin from the apparent difference.

대표청구항 ▼

1. A method for a rotorcraft provided with a turboshaft engine having a surveillance parameter, wherein the surveillance parameter has a guaranteed minimum value at a given engine operating condition when the engine is old, the method comprising: a) during a preliminary stage, operating the engine a

1. A method for a rotorcraft provided with a turboshaft engine having a surveillance parameter, wherein the surveillance parameter has a guaranteed minimum value at a given engine operating condition when the engine is old, the method comprising: a) during a preliminary stage, operating the engine at the given engine operating condition, monitoring the engine to obtain a current value of the surveillance parameter, and determining a preliminary comfort margin from a real difference equal to said current value during the preliminary stage minus said guaranteed value; andb) during a main stage, operating the engine and monitoring the engine to obtain a current value of the surveillance parameter, wherein the surveillance parameter has a limit value depending on the operation of the engine; andb1) determining a useful comfort margin from said preliminary comfort margin;b2) determining an apparent difference equal to the difference between the current value during the main stage and the limit value of said surveillance parameter; andb3) determining a limiting margin as being equal to the useful comfort margin subtracted from the apparent difference. 2. A method according to claim 1, wherein said main stage is performed continuously while said rotorcraft is in flight. 3. A method according to claim 1, wherein said preliminary stage is implemented solely when performing spot checks on the soundness of the engine. 4. A method according to claim 1, wherein said preliminary comfort margin is equal to said real difference, said useful comfort margin being equal to said preliminary comfort margin. 5. A method according to claim 1, wherein said preliminary comfort margin is estimated with a moving average by adding the real differences determined during the most recent preliminary stages and then dividing the resulting sum by the number of preliminary stages taken into consideration. 6. A method according to claim 5, wherein said number of preliminary stages taken into consideration lies in the range five to fifteen. 7. A method according to claim 1, wherein during step a), a transfer relationship is used to modulate said real difference as a function of conditions outside of the rotorcraft in order to obtain a modulated difference. 8. A method according to claim 7, wherein when the surveillance parameter is the speed of rotation of the gas generator of said turboshaft engine, said transfer relationship is the following first relationship in which “*” represents the multiplication symbol and ΔNG′, ΔNG, and T0 represent respectively the modulated difference, the real difference between the current value and the guaranteed minimum value for said speed of rotation, and the temperature outside the rotorcraft: Δ⁢⁢NG′=Δ⁢⁢NG*288T⁢⁢0 9. A method according to claim 7, wherein when the surveillance parameter is the ejection temperature of the gas at the inlet to the free turbine as developed by said turboshaft engine, said transfer relationship is the following second relationship in which “*” represents the multiplication symbol and ΔT′, ΔT, T0, and P0 represent respectively the modulated difference, the real difference between the current value and the guaranteed value of said ejection temperature, and the temperature and the pressure outside the rotorcraft: Δ⁢⁢T′=Δ⁢⁢T*((1013.25P⁢⁢0)β⁢⁢1*(288.15T⁢⁢0)β⁢⁢2) 10. A method according to claim 7, wherein when the surveillance parameter is torque developed by said turboshaft engine, said transfer relationship is the following third relationship in which “*” represents the multiplication symbol and ΔC′, ΔC, T0, and P0 represent respectively the modulated difference, the real difference between the current value and the guaranteed minimum value of said torque, and the temperature and the pressure outside the rotorcraft: Δ⁢⁢C′=Δ⁢⁢C*((1013.25P⁢⁢0)α⁢⁢1*(288.15T⁢⁢0)α⁢⁢2) 11. A method according to claim 7, wherein said preliminary comfort margin is equal to said modulated difference. 12. A method according to claim 7, wherein the preliminary comfort margin is estimated using a moving average, adding the modulated differences determined during the most recent preliminary stages and dividing the resulting sum by the number of preliminary stages taken into consideration. 13. A method according to claim 7, wherein when the preliminary comfort margin is determined by a modulated difference, during step b1), the useful comfort margin is estimated by replacing the preliminary comfort margin in the flying conditions of the rotorcraft using said transfer relationship. 14. A method according to claim 1, wherein when the surveillance parameter is the speed of rotation of the gas generator of the turboshaft engine, said guaranteed minimum value corresponds to the value that would be reached by said speed of rotation if the engine were an old engine. 15. A method according to claim 1, wherein when the surveillance parameter is the ejection temperature of the gas at the inlet to the free turbine of the turboshaft engine, said guaranteed minimum value corresponds to the value that said temperature would reach if the engine were an old engine. 16. A method according to claim 1, wherein when the surveillance parameter is the torque of the turboshaft engine, said guaranteed minimum value corresponds to the limit value of said torque at the operating speed of the engine. 17. A first limitation instrument for a rotorcraft provided with at least one turboshaft engine, said instrument comprising: acquisition sensors for acquiring current values of a plurality of surveillance parameters of said engine, wherein each surveillance parameter has a guaranteed minimum value at a given engine operating condition when the engine is old; anda processor configured to:a) during a preliminary stage while the engine is operating at the given engine operating condition, obtain from the sensors the current values of the surveillance parameters and, for each surveillance parameter, determine a preliminary comfort margin from a real difference equal to said current value during the preliminary stage minus said guaranteed value; andb) during a main stage while the engine is operating, obtain from the sensors the current values of the surveillance parameters, wherein each surveillance parameter has a limit value depending on the operation of the engine, and, for each surveillance parameter, determine in succession:b1) a useful comfort margin from said preliminary comfort margin;b2) an apparent difference equal to the difference between the current value during the main stage and the limit value of said surveillance parameter; andb3) a limiting margin as being equal to the useful comfort margin subtracted from the apparent difference. 18. A first limitation instrument according to claim 17, wherein said processor includes a secondary processor integrated in a main processor. 19. A first limitation instrument according to claim 17, including secondary sensors measuring outside conditions in order to ensure that the processor determines a modulated difference of said real difference as a function of the outside conditions. 20. A first limitation instrument according to claim 19, wherein said processor is provided with a memory suitable for storing the most recently determined modulated differences in order to take a moving average thereof. 21. A first limitation instrument according to claim 17, further comprising a display configured to display the value of said limiting margin. 22. A first limitation instrument according to claim 21, wherein said display value corresponds to said limiting margin of said limiting parameter converted into one of a power margin and a pitch margin.