Patent ID: 6497385
Filing Date: 2002-12-24
Classification: B64C

Abstract:
A rotor blade including a blade root for attachment to a rotor hub for rotating said blade about an axis of rotation transverse to a blade span R between said axis of rotation and a distal end of said blade defining a blade tip, wherein said blade has a chord extending between a blade leading edge and a blade trailing edge transverse to the blade span and said chord has a local geometric twist angle &thgr;=Æ’(r/R), with r being the distance along the blade span from said axis of rotation, said blade comprising:an inner region between an inner boundary at (r/R)inner=0.20Â±0.04 and a transition point at (r/R)trans=0.75Â±0.04, wherein &thgr;inner at (r/R)inner has a positive value and &thgr;inner is greater than or equal to &thgr;trans at (r/R)trans; and a tip region between the transition point and said blade tip, said tip region including: a first portion between (r/R)trans and (r/R)min>(r/R)trans, wherein &thgr; continuously decreases from &thgr;trans to &thgr;min at (r/R)min, and &Dgr;&thgr;tip1=|&thgr;minâˆ’&thgr;trans|>3Â°, and a second portion between (r/R)min and said blade tip, wherein &thgr; continuously increases from &thgr;min to &thgr;tip at said blade tip, and &Dgr;&thgr;tip2=|&thgr;tipâˆ’&thgr;min| is at least about 3Â° and no greater than about 20Â°.