Range and Endurance (Lesson Plan 4B)
For this PGI, the Background Knowledge section should begin with an examination of the Drag Curve and Power Curve described in the student’s Flight Training Manual. Begin by laying out the Drag Curve graph, and follow this with the Power Curve Graph. The two should be laid out, one above the other. One strategy to maintain student involvement is to sequentially draw on the whiteboard the lines that make up the graph, asking the student to recall what the line represents—accordingly, on the graph depicting the drag curve, the student is asked to identify speed as the horizontal axis, drag as the vertical axis, and the curved lines that represent induced drag, parasitic drag, and total drag. The lowest point of the total drag curve is the point of maximum lift/drag ratio, or maximum range, and it should be demonstrated that any variations from this speed will cause a rise of either induced or parasitic drag. It is good practice to relate the minimum drag to the maximum range by laying out the fundamental coupling of an aircraft—lift versus weight, and thrust versus drag—pointing out that if you can minimize drag, you can maximize the efficiency of thrust, or what is “forward speed”. Be sure to point out that the maximum lift/drag ratio is not a static state, but something that is subject to variation based on the state of the aircraft—weight, altitude, etc. The job of today’s flight is to identify it’s speed given the conditions of flight.