A new flight-test method has been developed for evaluating ground effect on fixed-wing aircraft. The method requires the pilot to fly at constant angle of attack and power setting during an approach to the runway at various initial sink rates. With this flight condition, lift, drag, and pitching moment are constant prior to approaching the ground. When ground effect is encountered, changes in flight path, velocity, and control-surf ace positions are interpreted as changes in lift, drag, and pitching moment, respectively. The fundamental principals and operational problems involved in applying this method are discussed in detail. The advantage of this technique is that the entire ground-effect characteristics of a configuration can be evaluated during a few approaches rather than by means of the multitude of flyby s required by the classical constant-altitude fly-by method. The method has been applied to two low-aspect-ratio aircraft: a straight-wing and a delta-wing configuration. Some of the results of these tests are presented and compared with wind-tunnel predictions to illustrate the quality of the data produced by this technique. Nomenclature a n = acceleration measured along the vertical axis of the aircraft, g units d x = acceleration measured along the longitudinal axis of the aircraft, g unitsacceleration due to gravity h = height of quarter chord above the ground h = vertical velocity h = vertical acceleration L = lift q = dynamic pressure, pV 2 /2 S = wing area T = aircraft net thrust t = time V = true airspeed W = aircraft weight x = horizontal velocity x = horizontal acceleration a = angle of attack 7 = flight-path angle &CD -drag-coefficient increment due to ground effect &CL = lift-coefficient increment due to ground effect d e = longitudinal control-surface deflection 6 = pitch attitude p -atmospheric density Subscript i = initial value
A glycol-exuding porous leading edge ice protection system was tested in the NASAIcing Research Tunnel at Lewis Research Center. Test results showed that the system was very effective in preventing ice accretion (anti-ice mode) or removing ice from an airfoil. Minimumglycol flow rates required for antiicing are a function of velocity, liquid water content in the air, ambient temperature, and droplet size. Large ice caps were removedin only a few minutes using anti-ice flow rates, with the shed time being a function of the type of ice, size of the ice cap, angle of attack, and glycol flow rate. Wake survey measurementsshowedthat no significant drag penalty was associated with the installation or operation of the system tested.
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