DESIGN IN FORMATION ON THE S-70A I UH-60 BLACKHAWK
a. Why does the main rotor blade have a swept tip? b. Why does the main rotor blade have a nonsymmetrical airfoil section approximately two thirds along it’s span? c. Why does the main rotor blade have a blade offset? d. Why does the main rotor system have a preset coning angle? e. Why does the main rotor system have a preset lag angle? f. Why is a reflex trailing edge used on the main rotor blade? g. Why is a blade root cutout used? h. Why were the tail rotor blades given the shape they have? i. Why is a delta hinge used on the tail rotor system? j. Why was the tail rotor system put on the right hand side of the vertical stabiliser? k. Why does the tail rotor system rotate with the bottom blade rotating forward? I. Why does the vertical stabiliser have the trailing edge partially cut out? m. Why use a stabilator and not a stabiliser? n. Why are there four cutouts in the stabilator tailing edge? o. Why is a mast extension used? p. Why are bifilars used? q. Why is the transmission tilted forward? r. Why is there an elastomeric bearing on the right hand side of the stabilator only?
a. Why does the main rotor blade have a swept tip? The swept tip has several advantages over a straight blade, some maybe not so clear or well defined: delay of compressibility effects aerodynamically increasing blade twist in a hover to increase hover performance aerodynamically untwisting the blade in forward flight to reduce susceptibility to ‘Mach tuck’ effects on the advancing side reduce main rotor noise reduce the adverse effect of vortex shedding The sweep back should delay compressibility effects. The effective sum of rotational speed and forward velocity seen by(perpendicular to) the a blade leading edge will be less than a straight blade.
This delay in compressibihty also reduces the noise effect
The primary reason for the decision to design a swept tip was to improve the hover performance. Blade twist in the...