Does a pusher configuration perfom better than ducted fan for the same airframe, consider for example the P-80, how would it perform better?

From : Don Stackhouse

That depends on the specific application, but for most model applications I'd say the answer is a guarded "yes". The key here is diameter. For low speed thrust, more diameter is better. Although at static situations a duct can help, a sufficiently bigger diameter will usually be more efficient than a duct, especially as the speed picks up a bit. Pushers tend to be limited on diameter in many situations than a comparable tractor prop, but they are still usually quite a bit bigger than a typical ducted fan. This gives them an advantage over the fan in those situations.

If the pusher prop and fan are limited to equal diameters, the picture changes. The fan's duct limits the tip losses at static and very low speed flight conditions, and provides some benefits in the way the fan can use its diameter (it allows for non-zero thrust at the tip of the blade), giving it better thrust at low speeds. As speed increases, the tip losses diminish, while the drag of the duct itself increases, until at some "crossover velocity" the drag of the duct becomes larger than the benefits it provides in tip losses. All other things being equal, above the crossover velocity the prop will be better, but below the crossover velocity, the fan will have an advantage.

Don Stackhouse
DJ Aerotech