Method and system for monitoring the level of oil contained in a tank of an aircraft engine

1. A method of monitoring a level of oil contained in a tank of an aircraft engine, the method comprising:

for at least two predetermined operating stages of the engine, during at least one mission of the aircraft:

measuring, by an oil level sensor, a plurality of measurements of an oil level of the tank,

measuring an oil temperature and an engine speed of rotation associated with each measurement of the oil level of the tank,

storing, in a memory of a first computer, the measurements of the oil level of the tank and the associated oil temperature and associated engine speed of rotation, and

selecting, using the first computer, measurements representative of oil level variations having both oil temperatures that are within a predetermined range of a reference temperature and engine speeds of rotation that are within a predetermined range of a reference speed of rotation corresponding to an iso-condition;

aggregating, using a second computer, only the measurements corresponding to the iso-condition selected over the operating stages during the at least one mission of the aircraft to produce a curve of the oil level of the tank; and

comparing, using the second computer, the curve produced by the aggregated measurements with reference data to identify abnormal oil consumption of the engine.

2. A monitoring method according to claim 1 , wherein the two predetermined operating stages of the engine correspond to a taxiing stage and to a cruising stage in the mission of the aircraft.

3. A monitoring method according to claim 1 , wherein, when selecting measurements, measurements that are representative of oil level variations that appear over a duration shorter than a predetermined limit duration are excluded.

4. A monitoring method according to claim 1 , wherein, when selecting measurements, oil level measurements greater than a predetermined limit oil level are excluded.

5. A monitoring method according to claim 1 , wherein, when selecting measurements, measurements representative of oil level variations greater than a predetermined limit variation are excluded.

6. A monitoring method according to claim 1 , wherein the aggregating the measurements includes detecting at least one filling of the tank between two successive missions of the aircraft.

7. A monitoring method according to claim 1 , wherein the aggregating the measurements includes correcting at least one oil level measurement as a function of a difference that exists between the oil temperature associated with the measurement and the reference temperature.

8. A monitoring method according to claim 1 , wherein the aggregating the measurements includes applying linear regression to the measurements.

9. A monitoring method according to claim 1 , wherein the aggregated measurements are compared relative to a predetermined threshold representative of abnormal consumption of oil by the engine.

10. A monitoring method according to claim 1 , wherein measurements are aggregated over a plurality of missions of the aircraft, and the aggregated measurements are compared with a reference curve representative of normal consumption of oil by the engine.

11. A monitoring method according to claim 1 , wherein:

measurements are obtained and selected during the mission of the aircraft; and

measurements are aggregated and compared by a device on the ground to which the selected measurements have been sent.

12. A monitoring system for monitoring the oil level contained in a tank of an aeroengine, the system comprising:

means that are activated for at least two predetermined operating stages of the engine during at least one mission of the aircraft:

for measuring a plurality of measurements of an oil level of the tank,

for measuring an oil temperature and an engine speed of rotation associated with each measurement of the oil level of the tank, and

for selecting measurements representative of oil level variations having both oil temperatures within a predetermined range of a reference temperature and engine speeds of rotation that are within a predetermined range of a reference speed of rotation corresponding to an iso-condition:

means for aggregating only the measurements corresponding to the iso-condition selected over the operating stages during the at least one mission of the aircraft to produce a curve of the oil level of the tank; and

means for comparing the curve produced by the aggregated measurements with reference data in order to identify abnormal oil consumption of the engine.

13. A monitoring system according to claim 12 , wherein:

the means for obtaining a plurality of measurements and for selecting the measurements representative of oil level variations are on board the aircraft; and

the means for aggregating the selected measurements and for comparing the aggregated measurements with reference data are incorporated in a device on the ground;

the aircraft further including means for sending the selected measurements to the device on the ground.