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A source-paneling body analysis computer program was modified to permit arbitrary panels to be opened to receive or exhaust cooling air flow. It was found that exhausting the cooling air into concave regions such as before the windshield or behind the canopy resulted in decreased drag, probably because of the streamlining effects of the airflow. This suggests that the drag of single-engine light aircraft could be reduced by redesigning the cowl to entrap air below the propeller axis and exhaust the cooling portion of it (but not the engine exhaust) through flush ports in front of the windshield.

The NCSU body flow computer program was modified to include the axial velocity component of propeller wakes. The energetic wake is represented by a series of ring vortices spaced along the body axis whose strengths are related to the engine power output and whose diameters are always larger than the maximum local body dimension. Agreeing at least qualitatively with limited full-scale wind tunnel data, the results indicated that aircraft drag increases linearly with power level for a given configuration.

Progress is reported in the development of a method to extract thrust horsepower and drag simultaneously from accelerated flight maneuvers. Although the flight data still is not as self-compatible as desired, the extracted drag and power obtained from a pullup-pushover agree reasonably well with the results from steady flight determinations for drag and wind tunnel tests for power. In the level flight acceleration only the extracted CDO value agrees closely. Further work is necessary to define the proper power model and to make the level flight acceleration data more self-compatible.

Drag and power information extracted by a new method from accelerated flight test data on an advanced technology light twin airplane are compared with drag results taken by the usual speed-power method. Agreement is fair at low angles of attack and poor at high angles of attack. The new method requires accurate input data for good results and some inconsistencies still remain in these data. As a consequence, the results obtained by the new method must be regarded as tentative at this time.

The bases for computer programs which calculate by rigorous analytical methods the lift and drag of light aircraft are indicated along with results obtained for airfoils, complete wings, and fuselages. A method to determine the actual lift, drag, and thrust horsepower experienced during flight is discussed in detail. The latter will be used to verify the analytical predictions for an advanced technology light twin.

The process leading to the development of efficient computer programs for predicting the performance and riding and handling qualities of light aircraft is described. The riding and handling qualities program permits one to specify only the aircraft geometry and to obtain as output the motion that geometry will produce in response to one of five specific control surface deflections. The performance programs fit both power available and drag data with high-order polynomials for accuracy. Conventional, static performance and integrations of the nonlinear equations of motion (so-called path performance) are then obtained. Present efforts are directed toward computerizing the prediction of lift and drag given the aircraft geometry, so that by specifying the geometry one can immediately determine both the performance and the riding and handling qualities.