AERODYNAMIC DESIGN OF ADVANCED ROTORS WITH NEW TIP SHAPES

Aerodynamic design of advanced helicopter main rotors with respect to blade section, twist, tip shape is discussed with special emphasis on wind tunnel tests results and analysis. Three four meter diameter model rotors with different ONERA - AEROSPATIALE (OA) blade section distributions are compared at high speed, beyond 180 kts in terms of performance, from MODANE wind tunnel tests. Comparison with predicted performances is also presented. Tip shape studies at ONERA and AEROSPATIALE are discussed. They include wind tunnel tests on model scaled rotors as well as flight tests and 3D unsteady analysis. General results obtained on current blade tip shapes are reviewed. Larger gains are demonstrated in forward flight with more sophisticated tip planform such as swept parabolic tips which are presently undergoing tests in the ONERA Chalais-Meudon wind tunnel. The main conclusions of these tests as well as correlation with the 3D transonic unsteady or quasi-steady analysis are presented in the last version of the code that includes non lifting and lifting capability. Recommandations are made on the basis of these studies. Further investigations are planned on aeroelastic coupling, active twist and hover performance. Additional data is required and will be obtained during the experimental Gazelle 349 flight test program which is outlined.