A main rotor blade assembly comprising: an inboard section, an intermediate section outboard of said inboard section, and an outboard section outboard of said intermediate section, characterized in that said outboard section comprises: an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 20% of the main rotor blade assembly; or an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 25% of the main rotor blade assembly; or an airfoil section extending along the outer 15% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 10% of the main rotor blade assembly; or an airfoil section extending along the outer 10% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 8% of the main rotor blade assembly. an inboard section, an intermediate section outboard of said inboard section, and an outboard section outboard of said intermediate section, characterized in that said outboard section comprises: an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 20% of the main rotor blade assembly; or an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 25% of the main rotor blade assembly; or an airfoil section extending along the outer 15% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 10% of the main rotor blade assembly; or an airfoil section extending along the outer 10% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 8% of the main rotor blade assembly. an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 20% of the main rotor blade assembly; or an airfoil section extending along the outer 25% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 25% of the main rotor blade assembly; or an airfoil section extending along the outer 15% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 10% of the main rotor blade assembly; or an airfoil section extending along the outer 10% of the main rotor blade assembly and having a pitching moment coefficient more negative than -0.035 at Mach numbers below 0.8; and a chord taper section extending along the outer 8% of the main rotor blade assembly.