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. Longi¬tudinal 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.nThe bypass ratio (BPR) 6.2 engine simulator provided the best lift and drag character¬istics of the five simulators tested in the take-off and landing configurations. The poor per¬formance 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 con¬figuration 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 and landing configurations required a high-lift tail.
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