## The Drag Polar

Welcome to Part 9 in the Fundamentals of Aircraft Design series. In the previous posts we have covered the fundamentals of flight, studied the wing, fuselage and empennage, and have been introduced to aerodynamic lift, drag and moment coefficients. Now we put it all together and run through a preliminary drag estimation of a new aircraft design. Let’s get started!

## Aircraft Engine and Propeller Sizing

Welcome to Part 10, the final installment in the Fundamentals of Aircraft Design series. In Part 9 we completed a preliminary drag estimation of a new light sport aircraft design. In this tutorial we build on from the drag estimation, and specify an engine and propeller combination in order to determine the variation in thrust with airspeed. By superimposing this thrust curve onto the drag graph, we can calculate the aircraft’s theoretical maximum speed, or speed at various engine power settings. Let’s get started!

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## Lifting Surface Correction Factor

The calculation below provides an estimation of the lifting surface correction factor used when compiling an estimation of the zero lift drag produced by the wing. This is described in the tutorial on the Drag Polar. The graph shown below was originally published in USAF Stability and Control Datcom [1] and reproduced in Roskam Part VI Chapter 4.2 [2]. The calculator provides an estimation of the correction factor based on the digitization of the graph and an interpolation between datapoints. The methodology is described below.
` Continue reading "Lifting Surface Correction Factor"`