Benchmark 

Enter basic information about the airplane. While this information is about the F.8L Falco, Benchmark can handle any piston engine airplane with a constantspeed propeller. The Cdo is the coefficient of drag at zero lift, also known as profile drag coefficient. This value is calculated in the drag polar flight test analysis, but if you want to type your own value to use as a design study, go ahead. You can also use the known drag of an existing airplane and then add or subtract drag from the airplane in the Airplane Speed Calculator to match the drag of the airplane to your own airplane. This allows you to use an existing design as the basic for your airplane model and allows you to avoid the difficult work involved in drag polar drag tests and analysis. Oswald E is the other critical value used in the speed calculations of the airplane, and like Cdo it is automatically calculated in the drag polar flight test analysis. Oswald E is a glorified fudge factor. The Prandtl wing theory is the aeronautical engineering basis for all performance calculations of an airplane, however the original Prandtl wing theory assumed a 'perfect' elliptical wing. But few wings are elliptical, so the Oswald Efficiency Factor, or 'Oswald E' was invented to accommodate lessthanperfect wings. So an Oswald E of 0.65 may be thought of as 65% of perfection. The Oswald E would be 1.0 for an ellipticallyloaded wing with no liftdependent viscous drag, but for practical aircraft if varies from about 0.75 to 0.90. The Oswald E can never be above 1.0. Ram Recovery is the ability of the induction system to convert ram air pressure into a boost of manifold pressure. Ordinarily you would determine this with a simple flight test and then use Benchmark's Ram Recovery Flight Test to calculate this. You may drag a photo of your plane and drop it into the program. You may use any size photo, but be aware that this will affect the file size. In the example above, we used a 720 x 500 pixel jpeg image, 72 dpi. 
