LH WIND TUNNEL TESTING: KEY TO ADVANCED AERODYNAMIC DESIGN

The Boeing Sikorsky LH design includes many advanced aerodynamic features developed and refined from extensive wind tunnel testing. Over 10,000 hours of testing related to the LH design have been conducted from 1978 to 1990. The testing included two dimensional airfoil evaluations, unpowered drag and stability models, isolated main rotor and FANTAIL™ powered models and complete rotor/airframe interaction models with a main rotor, fuselage and FANTAIL™ system. Powered model testing at 1/4 scale was used to define the LH five-bladed BMR configuration. Based on these data a swept tapered planform with a nominal twist of 13 degrees was selected. A combination of Boeing and Sikorsky advanced airfoils were selected based on two-dimensional wind tunnel testing. Complete rotor/interaction models were used to provide data for fan trade studies. The FANTAIL™ performance, stability, loads and acoustic characteristics were verified by 3/4 scale FANTAIL™ testing in hover and forward flight. Numerous 1/6 and 1/10 scale unpowered fuselage model tests were conducted to assist in the airframe, empennage, hub and fan duct development. This reliance on wind tunnel testing was part of the Boeing Sikorsky risk reduction effort.