Profile for helicopter blade - raises mach number at which drag divergence occurs and increases life co-efficient

摘要

The profile of the blade of a helicopter rotor has the radius Ro of the curvature of the leading edge designed as a function of the chord C and the square of the maximum thickness max. (Ro=1.7Ce2max). The curvature of the undersurface near the leading edge, decreases rapidly for a distance equal to a few percent of the chord. This first zone then runs into a second zone of very slight curvature which extends for 20 percent of the chord. The curvature decreases to a minimum at the end of this second zone.. The Mach number, at which drag divergence occurs, is raised and the co-efficient of lift at this Mach number is also increased. This design of helicopter blade profile improves the performance of the helicopter at high forward speed and when hovering, without affecting its aerobatic capability. It also prevents shock waves at the leading edge being generated.