Method of inspecting impacts observed in fan casings

1. A method for inspecting impacts present on an internal face of a fan casing, said method comprising:

spotting a first impact present in the internal face of the fan casing;

delimiting an inspection area including said first impact;

spotting different impacts present on the delimited inspection area, said different spotted impacts forming a set of impacts to be considered;

measuring, for each impact to be considered, the depth and length of said impact;

for each impact to be considered, determining a level of harmfulness value, using at least one chart relating the depth and length of each impact to be considered to a level of harmfulness, wherein for the depth of the impact, the chart provides different levels of harmfulness that depend on the length of the impact;

determining, for the inspection area including the first impact, a total level of harmfulness value by adding the level of harmfulness determined for each impact to be considered.

2. The method according to claim 1 , wherein delimiting the inspection area containing the first impact is performed by a mask.

3. The method according to claim 2 , wherein the mask is rectangular in shape and has the following characteristics:

a first side of the mask has a dimension between a fifth part of a chord of casing vanes and the length of the chord of said vanes;

a second side of the mask has a dimension between the fifth part of the chord of said vanes and the height of a blade of said vanes.

4. The method according to claim 2 , wherein the dimensions of the mask depend on the location of the inspection area, a first mask having first dimensions being used for an upstream zone of the casing and/or a second mask having second dimensions being used for an abradable zone of the casing and/or a third mask having third dimensions being used for a downstream zone of the casing.

5. The method according to claim 4 , wherein the first mask is rectangular in shape, having a length 71 millimeters within ten percent, and a width 20 millimeters within ten percent, and/or the third mask is square in shape, having a side 250 millimeters within ten percent.

6. The method according to claim 5 , wherein each mask is associated with a specific chart used for determining a level of harmfulness from depth and length information of each impact to be considered.

7. The method according to claim 1 , wherein delimiting the inspection area containing the first impact is performed by tracers and an associated calculator.

8. The method according to claim 1 , wherein each chart relates a measured value of the depth of the impact to be considered and a range of values comprising a measured value of the length of the impact to be considered to a level of harmfulness.

9. The method according to claim 8 , wherein the range of values comprising the measured value of the length of the impact to be considered has an amplitude of at least 5 millimeters for impacts having a length lower than 30 millimeters.

10. The method according to claim 1 , comprising, prior to the measuring, excluding from the set of impacts to be considered the impacts having a depth lower than 0.1 millimeters.

11. The method according to claim 1 , wherein the chart correlates the level of harmfulness to the depth of the impact for different ranges of lengths of impacts.