Method of fabricating a spar for a rotorcraft blade

1. A method of fabricating a rotorcraft blade provided with a rigid attachment filler ( 1 ) and with a spar ( 40 ) that extends along the span of the blade from a root ( 51 ) of the blade to a free end ( 52 ) of the blade, said attachment filler ( 1 ) having top, bottom, front, rear, left side, and right side faces ( 2 , 3 , 4 , 5 , 7 , and 6 ), wherein said spar ( 40 ) includes a succession of fiber layers ( 31 , 32 , 33 ) that hold said attachment filler ( 1 ) captive at the root ( 51 ) of said blade, said spar ( 40 ) being secured to said top, bottom, front, rear, and left side faces ( 2 , 3 , 4 , 5 and 7 ) of said attachment filler ( 1 ), the method comprising the following steps in particular and in succession:

a) securing a first support shaft ( 8 ) to a rigid attachment filler ( 1 ) of the blade that is reversibly fastened to a mandrel ( 20 );

b) placing fibers around said attachment filler ( 1 ) and said mandrel ( 20 ) in order to fabricate a spar of said blade, said spar ( 40 ) then including a succession of fiber layers ( 31 , 32 , 33 ) that hold said attachment filler ( 1 ) captive at the root ( 51 ) of said blade; and

c) removing said first shaft ( 8 ) after the spar has polymerized.

2. A fabrication method according to claim 1 , wherein step c) further comprises cutting off the distal end ( 47 ) of the resulting spar ( 40 ), i.e. the distal end ( 47 ) of the spar ( 40 ) that is remote from said attachment filler ( 1 ), in order to remove said mandrel ( 20 ).

3. A fabrication method according to claim 1 , wherein a portion ( 8 ′) of the first shaft ( 8 ) projects from the attachment filler ( 1 ) at the end of step c), and the first shaft is removed, the method further comprising cutting through the fibers that were covering said projecting portion ( 8 ′).

4. A method according to claim 1 , wherein step d) further comprises piercing the spar ( 40 ) through the attachment filler ( 1 ) in order to pass at least one pin for fastening the blade to a rotor hub.

5. A method according to claim 4 , further comprising forming at least one orifice ( 9 ′, 9 ″) in the attachment filler prior to step a), so as to be in register with the piercing ( 46 ′, 46 ″) performed during step d).

6. A fabrication method according to claim 1 , wherein the mandrel ( 20 ) has a rigid core ( 21 ) surrounded by a meltable zone ( 22 ) covered in an inflatable bag ( 23 ), the method further comprising intermediate step b′) destroying said meltable zone ( 22 ) at least in part so as to be able to remove the mandrel ( 20 ) subsequently, step b′) between steps b) and c).

7. A fabrication method according to claim 1 , wherein step a) further comprises securing said mandrel ( 20 ) to a second support shaft ( 10 ).

8. A fabrication method according to claim 7 further comprising securing the first and second support shafts ( 8 , 10 ) to each other and constituting a single common support shaft.