Rotor blade tip design for improved hover and cruise performance
A rotor blade for a rotary wing aircraft and a tip for the rotor blade. The rotor blade includes a blade root, a blade tip and a blade body that extends from the blade root to the blade tip. The blade tip includes: a continuously swept leading edge, a compound trailing edge, and a continuous anhedral.
1. A rotor blade for a rotary wing aircraft, comprising:
a blade root;
a blade tip; and
a blade body that extends from the blade root to the blade tip, the blade body defining a feathering axis;
wherein the blade tip comprises a continuously swept leading edge, a compound trailing edge, and a continuous anhedral, the compound trailing edge including a first trailing edge and a second trailing edge outboard of the first trailing edge and forming an intersection with the first trailing edge, the first trailing edge being parallel to a feathering axis of the blade and the second trailing edge tapering forward and extending to an outermost edge of the blade tip.
2. The rotor blade of claim 1 , wherein the anhedral of the rotor blade begins at r/R=0.96 and the anhedral angle at the tip edge is between about −20 degrees and −40 degrees, where R is a length of the rotor blade from root to tip and r is a length measured from the root of the rotor blade.
3. The rotor blade of claim 1 , wherein the first trailing edge extends from r/R=0.90 to r/R=0.96, and the second trailing edge tapers forward from r/R=0.96 to r/R=1, where R is a length of the rotor blade from root to tip and r is a length measured from the blade root.
4. The rotor blade of claim 1 , wherein the leading edge sweeps backward continuously beginning at r/R=0.90.
5. The rotor blade of claim 1 , wherein the leading edge further comprises a first leading edge that tapers forward away from the feathering axis between about r/R=0.91 and r/R=0.92 and a second leading edge that sweeps backward towards the feathering axis continuously for locations greater than r/R=0.92.
6. The rotor blade of claim 1 , wherein the outermost edge of the tip is a flat edge perpendicular to the feathering axis of the body of the rotor blade.
7. The rotor blade of claim 1 , wherein the tip of the blade further includes a twist angle of the blade with respect to the feathering axis.
8. A rotary wing aircraft that includes the rotor blade of claim 1 .
9. A tip of a rotor blade, the tip comprising:
a continuously swept leading edge;
a compound trailing edge including a first trailing edge and a second trailing edge outboard of the first trailing edge and forming an intersection with the first trailing edge, the first trailing edge being parallel to a feathering axis of the rotor blade and the second trailing edge tapering forward and extending to an outermost edge of the tip; and
a continuous anhedral, wherein a blade body extends from a blade root to the tip.
10. The tip of claim 9 , wherein the anhedral begins at r/R=0.96, where R is a length of the rotor blade from root to tip and r is a length measured from the root of the rotor blade.
11. The tip of claim 9 , wherein the anhedral angle at the tip edge is in a range between about −20 degrees to about −40 degrees.
12. The tip of claim 9 , wherein the first trailing edge extends from r/R=0.90 to r/R=0.96 and the second trailing edge tapers forward from r/R=0.96 to r/R=1, where R is a length of the rotor blade from root to tip and r is a length measured from the root of the rotor blade.
13. The tip of claim 9 , wherein the leading edge sweeps backward continuously beginning at r/R=0.90.
14. The tip of claim 9 , wherein the continuously swept leading edge further comprises a first leading edge that tapers forward between about r/R=0.91 and r/R=0.92 and a second leading edge that sweeps backward continuously for locations greater than r/R=0.92.
15. The tip of claim 9 , wherein the outermost edge of the tip is a flat edge perpendicular to the feathering axis of the body of the rotor blade.