Results from a wind-tunnel investigation of a large-scale externally blown flap model are presented. The model was equipped with four turbofan engines, a triple-slotted flap system, and a T-tail. The wing had a quarter-chord sweep of 25 deg, an aspect ratio of 7.28, and a taper ratio of 0.4. Aerodynamic loads and load distributions were determined from a total of 564 static pressure orifices located on the upper and lower surfaces of the slat, wing, and flaps. Loads are presented for variations of angle of attack, engine thrust setting, and flap deflection angle. In addition, the experimental results are compared with analytical results calculated by using a potential flow analysis.

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Wind tunnel investigation of aerodynamic loads on a large-scale externally blown flap model and comparison with theory

An investigation has been made to determine the chordwise and spanwise pressure distributions of a small-scale upper-surface blown jet-augmented flap STOL model The model was powered by two simulated high-bypass-ratio turbofan engines mounted ahead of and above an unswept-untapered wing in a nacelle having a rectangular nozzle The results of the investigation are presented as tabulated and plotted chordwise pressure distribution coefficients for nine spanwise stations

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Pressure distribution of a twin-engine upper-surface blown jet-flap model

An investigation of a four-engine externally blown flap (EBF) powered-lift transport was conducted in the Langley V/STOL tunnel to determine the effect of different engine configurations on the longitudinal aerodynamic characteristics. The different engine configurations were simulated by five different sets of propulsion simulators on a single aircraft model. Longitudinal aerodynamic data were obtained for each simulator on each flap deflection corresponding to cruise, take-off, and landing at a range of angles of attack and various thrust coefficients. The bypass ratio (BPR) 6.2 engine simulator provided the best lift and drag characteristics of the five simulators tested in the take-off and landing configurations. The poor performance of the BPR 10.0 and 3.2 engine simulators can be attributed to a mismatch of engine-model sizes or poor engine location and orientation. Isolated engine wake surveys indicated that a reasonable assessment of the aerodynamic characteristics of an engine-wing-flap configuration could be made if qualitative information were available which defined the engine wake characteristics. All configurations could be trimmed easily with relatively small horizontal-tail incidence angles; however, the take-off landing configurations required a high-lift tail.

Longitudinal aerodynamic characteristics of an externally blown flap powered lift model with several propulsive system simulators

Two wind-tunnel investigations were conducted at Langley Research Center to determine the effect of dif- ferent wake characteristics on the performance of two separate externally blown flap transport configurations. In both cases, the thrust removed lift coefficient could be directly related to the proportion of momentum cap- tured by the flap system. In another investigation of an externally blown flap transport configuration, tufts were used to measure the upwash angles ahead of the wing. Using the thrust-removed lift coefficient, a simple vortex- lattice method provided a good approximation of these angles away from the nacelle inlets. Nomenclature = total area of jet wake which impinges flap m2 = incremental area of jet wake which impinges flap m2 = total area of jet wake at flap m2 = local wing chord m = lift coefficient, lift/^s1 = thrust removed lift coefficient = thrust coefficient, thrust/qs = engine-exhaust-flap impingement parameter = free-stream dynamic pressure N/m2 = incremental portion of jet which impinges flap, N/m2 = jet dynamic pressure at flap location, N/m2 = upper-half radius of nacelle, m = wing area, m2 = static thrust, N = vertical distance, m = angle of attack, degrees = nominal flap deflection angle, degrees =jet exhaust deflection (measured from body axis), tan;1 (normal force/axial force), degrees = inflow angle, with respect to model horizontal axis, degrees = static thrust recovery efficiency, ((normal force)2 + (axial force)2 ) 1/2/T = upflbw angle, with respect to freestream degrees = bypass ratio = externally blown flap The present paper describes the results of a relatively simple analysis based on an engine exhaust flap area impingement parameter, which is a function of the distribution of dynamic pressure impingement on the flap, the area of the flap im- pingement, the total area of the engine exhaust, and the thrust. Isolated engine wake surveys were conducted to define this parameter for one of the EBF models for which aerodynamic performance data were available.2 A uniform dynamic pressure profile was assumed to determine this parameter for the other EBF model correlation with aerodynamic performance data. n A high-lift system, such as an EBF, induces large upflow angles in front of the wing in the region of the nacelle inlets. These flowfields must be defined in order that the nacelles be properly designed to minimize flow distortion at the engine face. This paper also presents the results of an investigation to measure the flow angle near the engine inlets of a represen- tative EBF model. The vortex-lattice method14 was used to calculate these upflow angles, to determine if they could be predicted.

Propulsion Characteristics Affecting the Aerodynamic Performance of an Externally Blown Flap Transport Model

An investigation has been conducted to determine the effects of flap span and wing aspect ratio on the static longitudinal aerodynamic characteristics and chordwise and spanwise pressure distributions on the wing and trailing-edge flap of a straight-wing STOL model having an externally blown jet flap without vertical and horizontal tail surfaces. The force tests were made over an angle-of-attack range for several thrust coefficients and two flap deflections. The pressure data are presented as tabulated and plotted chordwise pressure-distribution coefficients for angles of attack of 1 and 16. Pressure-distribution measurements were made at several spanwise stations.

C. C. Smith

Papers

Effect of wing aspect ratio and flap span on aerodynamic characteristics of an externally blown jet-flap STOL model