Fan blade leading edge sheath

1 . A sheath, comprising:

a leading edge portion having pressure and suction sides for respective association with pressure and suction sides of an airfoil; and

first and second wings respectively extending from the pressure and suction sides of the leading edge portion,

the first wing comprising a first elongate portion, which is configured to extend along in contact with the pressure side, and a first trailing edge, which is configured to extend along in contact with the pressure side and which is disposed at an end of and thinned inwardly toward the pressure side relative to the first elongate portion, and

the second wing comprising a second elongate portion, which is configured to extend along in contact with the pressure side, and a second trailing edge, which is configured to extend along in contact with the pressure side and which is disposed at an end of and thinned inwardly toward the pressure side relative to the second elongate portion.

2 . The sheath according to claim 1 , wherein an aft edge of the leading edge portion and respective interior surfaces of the first and second wings form a cavity for receiving a leading edge of the airfoil.

3 . The sheath according to claim 1 , further comprising sheath adhesive by which the sheath is attachable to a leading edge of the airfoil.

4 . The sheath according to claim 1 , wherein the first and second wings have different chordal lengths.

5 . The sheath according to claim 1 , wherein respective profiles of each of the first and second trailing edges are curvilinear.

6 . The sheath according to claim 5 , wherein:

the first trailing edge comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the pressure side;

a downstream section of a high aspect ratio thinning slope, which terminates at the pressure side; and

a first intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section, and

the second trailing edge comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the suction side;

a downstream section of a high aspect ratio thinning slope, which terminates at the suction side; and

a second intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section.

7 . The sheath according to claim 6 , wherein:

the first trailing edge comprises surface features arrayed along the first intermediate section to grip an overlying erosion coating, and

the second trailing edge comprises surface features arrayed along the second intermediate section to grip an overlying erosion coating.

8 . An airfoil assembly, comprising:

an airfoil having a leading edge and pressure and suction sides extending from the leading edge; and

a sheath affixed to the leading edge of the airfoil and comprising:

a leading edge portion having pressure and suction sides respectively associated with the pressure and suction sides of the airfoil;

a first wing extending from the pressure side of the leading edge portion and comprising a locally-thinned trailing edge, which is thinned inwardly toward the pressure side;

a second wing extending from the suction side of the leading edge portion and comprising a locally-thinned trailing edge, which is thinned inwardly toward the suction side; and

an erosion coating applied to the pressure and suction sides of the airfoil to overlap with the respective locally-thinned trailing edge of each of the first and second wings.

9 . The airfoil assembly according to claim 8 , wherein an aft edge of the leading edge portion and respective interior surfaces of the first and second wings form a cavity in which the leading edge of the airfoil is received.

10 . The airfoil assembly according to claim 8 , wherein the airfoil comprises metallic materials and the airfoil assembly further comprises:

sheath adhesive to affix the sheath to the leading edge of the airfoil; and

primer interposed between the erosion coating and the airfoil.

11 . The airfoil assembly according to claim 8 , wherein the erosion coating comprises polyurethane.

12 . The airfoil assembly according to claim 8 , wherein the first and second wings have different chordal lengths.

13 . The airfoil assembly according to claim 8 , wherein:

the first wing comprises an elongate portion which extends along in contact with the pressure side,

the locally-thinned trailing edge of the first wing extends along in contact with the pressure side and is disposed at an end of and is thinned inwardly toward the pressure side relative to the elongate portion of the first wing,

the second wing comprises an elongate portion which extends along in contact with the suction side, and

the locally-thinned trailing edge of the second wing extends along in contact with the suction side and is disposed at an end of and is thinned inwardly toward the suction side relative to the elongate portion of the second wing.

14 . The airfoil assembly according to claim 8 , wherein respective profiles of the locally-thinned trailing edge of each of the first and second wings are curvilinear.

15 . The airfoil assembly according to claim 14 , wherein;

the locally-thinned trailing edge of the first wing comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the pressure side;

a downstream section of a high aspect ratio thinning slope, which terminates at the pressure side; and

a first intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section, and

the locally-thinned trailing edge of the second wing comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the suction side;

a downstream section of a high aspect ratio thinning slope, which terminates at the suction side; and

a second intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section.

16 . The airfoil assembly according to claim 15 , wherein:

the locally-thinned trailing edge of the first wing comprises surface features arrayed along the first intermediate section to grip onto the erosion coating, and

the locally-thinned trailing edge of the second wing comprises surface features arrayed along the second intermediate section to grip onto the erosion coating.

17 . An airfoil assembly method for use with an airfoil having a leading edge and pressure and suction sides extending from the leading edge, the airfoil assembly method comprising:

forming a sheath to comprise;

a leading edge portion having pressure and suction sides respectively associated with the pressure and suction sides of the airfoil;

a first wing extending from the pressure side of the leading edge portion and comprising a locally-thinned trailing edge, which is thinned inwardly toward the pressure side; and

a second wing extending from the suction side of the leading edge portion and comprising a locally-thinned trailing edge, which is thinned inwardly toward the suction side;

adhering the sheath to the leading edge of the airfoil; and

applying an erosion coating to the pressure and suction sides of the airfoil to overlap with the locally-thinned trailing edge of each of the first and second wings.

18 . The airfoil assembly method according to claim 17 , wherein the forming of the sheath comprises curvilinearly thinning the locally-thinned trailing edge of each of the first and second wings such that:

the locally-thinned trailing edge of the first wing comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the pressure side;

a downstream section of a high aspect ratio thinning slope, which terminates at the pressure side; and

a first intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section, and

the locally-thinned trailing edge of the second wing comprises:

an upstream section of a high aspect ratio thinning slope, which is distant from the suction side;

a downstream section of a high aspect ratio thinning slope, which terminates at the suction side; and

a second intermediate section of a low aspect ratio thinning slope, which is axially interposed between the upstream section and the downstream section.

19 . The airfoil assembly method according to claim 17 , wherein the applying of the erosion coating is executed such that the erosion coating at least initially overlaps with respective entireties of the locally-thinned trailing edge of each of the first and second wings.

20 . The airfoil assembly method according to claim 17 , further comprising priming the pressure and suction sides of the airfoil prior to the applying of the erosion coating.