Flight test measurements of the performance of the UH-60 Black Hawk helicopter with both standard and advanced rotors are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II. In general, the calculated power coefficient shows good agreement with the flight test data. However, the accuracy of the calculation degrades at high gross weight for all of the configurations. The analysis shows fair to good correlation for collective and longitudinal cyclic angles and pitch attitude, and poor to fair correlation for the lateral trim quantities (lateral cyclic angle and roll attitude). The increased solidity of the wide chord blade appears to be a dominant factor in the performance improvement at high gross weight by reducing blade loading and thus delaying stall.

S. Ar118y Ae~oJ7i~/~trly,~unrics Directorore (AMCOM) Mofitt Field, Culi/ortiiu Three flight conditions from the UH4OA Airloads Program are examined where dynamic stall occurs on the rotor: a symmetric pull-up that includes non-zero angular rates and accelerations; a high-speed, diving turn that includes non-zero angular rates, but nominally zero angular accelerations; and a level flight case with zero angular rates and accelerations. The hvo maneuver conditions result in severe pitch-link loads and represent design conditions for this military aircraft. Dynamic stall characteristics are identified in the section lift, the section pitching moment, and the trailing edge pressure and are used to create rotor disk maps that show the location and behavior of dynamic stall for this rotor. The measured blade pressures are used to examine the dynamic stall process itself and airfoil maps are developed that show the behavior of the dynamic stall vortex on the blade and its interaction with areas of supercritical flow. It is shown that the torsional dynamics of the rotor control wheredynamic stall may occur, while the flight condition and the resulting aerodynamic inflow determine ~vlretlier it will occur. Notation a speed of sound, Wsec b number of blades CL lift coefficient '~rnax maximum static lift coefficient C~ moment coefficient q M / o = -Ma torsion moment coefficient n(rpn2R5

Two airfoils are used on the main rotor blade of the UH-60A Black Hawk helicopter, the SC1095 and the SC1094 R8. Measurements of the section lift, drag, and pitching moment were obtained in ten wind tunnel tests for the SC1095 airfoil, and in five of these tests, measurements were also obtained for the SC1094 R8. The ten wind tunnel tests are characterized and described in the present study. Fundamental parameters derived from test measurements are compared and an assessment is made of the adequacy of the test data for use in look-up tables required by lifting-line calculation methods.

Maneuver data obtained under the NASAIArmy UH-60A Airloads Program are examined qualitatively to show the effects of maneuvering flight conditions on rotor loads. l b o test conditions have been selected for review based on a comparison of all 68 maneuver conditions flown in the test program. These two conditions were selected because they ranked in the top ten for rotor load severity and show two different types of non-linear aerodynamic behavior, three-dimensional compressibility and dynamic stall. A detailed assessment of the section lift and moment calculated from measured pressures for each condition is used to provide insight into these two phenomenon. Notation P advance ratio GW P air density, slug/ft3 &=gross weight coefficient LJ rotor solidity, bdnR (.082i) o nupQ2R4 n rotor rotational speed, radtsec 2L M2CL = section normal force coefficient

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