An investigation has been conducted to determine the effects of operating propellers on the longitudinal characteristics of a four-engine tractor airplane configuration having a 40° swept wing with an aspect ratio of 10. Results of wind-tunnel tests of a model representing such an airplane configuration (recently published) have shown these effects to be of most concern in the low-speed high-thrust flight regime. In the present report these data are analyzed to determine the source of the various effects and to indicate how the adverse effects' can be reduced. The data on which the analysis is based were obtained in tests of a semispan model with reflection-plane mounting, representing the right-hand side of a hypothetical airplane. Single-rotation, right-hand propellers were operated at values of thrust coefficient ranging from 0 to 0.9 per propeller. The thrust coefficient was sufficient to simulate 10,000 horsepower per engine at sea level at speeds down to 120 miles per hour, assuming the model to be l/l2 scale. Variations in the model geometry included several heights and incidences of the horizontal tail as well as tail removed two arrangements of extended split flaps, several propellerblade angles, and independent as well as simultaneous operation of the inboard and outboard propellers.
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