Flight Evaluation: Elliott Dual-Axis Low Airspeed System (LASSIE II)

Tests were conducted to evaluate the airspeed and direction-sensing capability of the Elliott low airspeed sensing and indicating equipment system (LASSIE II). The system included the basic dual-axis probe, an electronic package including a linearization circuit, a pressure altitude sensor, and a vertical speed computer. The probe is a pivoted vane designed to align with resultant flow and incorporates equipment which measures angles in all directions from the vertical. The probe also measures total and static pressures. The measured data are used to calculate airspeed components, sideslip angle, altitude, and vertical motion. The tests were conducted in an NUH-1M helicopter at Bishop, Oxnard, and Edwards Air Force Base, California, from December 1972 to September 1974. In its final configuration, the system provided repeatable airspeed components that were essentially linear except when operating in ground effect. The system also provided altitude and vertical motion information that was superior to that obtained from the aircraft standard systems. Incorporation of an ambient temperature probe and calculation of the true airspeed and angle of attack would yield a complete air data system.