At full power and with the long lever arm of a single pusher prop on a central fuselage (think LearAvia Learfan), the aircraft becomes stiff as a brick. Since a regular airplane needs to have basic stability with the engine running at idle, any additional stability change due to propeller placement comes on top. The stabilizing effect increases in proportion to the propeller surface area and the thrust, of course. THAT is why almost all high-powered, singe-engined aircraft have their propeller in the front: Maneuverability! Especially for a fighter aircraft, this is the opposite of what you want. A pusher propeller influences stability much as an additional tail, but without control surfaces. More disadvantages are the pilot risking to hit the propeller in an emergency bail-out and increased stability of the aircraft. If you cannot really rotate, takeoffs and landings are high-speed affairs. The main disadvantage for a single-engined aircraft, the reduced tail clearance, has already been mentioned. Also, the prop wash helps to increase the lift from flaps. They were placed in the prop wake and this gave much better directional control at low speed on the ground. On the other hand, the puller prop will help to maneuver the plane on the ground (this is a big benefit for taildraggers - note how many two-engined, taildragger airplanes have an H-tail (two rudders as endplates of the stabilizer). In case of the Do-335 (see picture below), the single-engine top speed was 30 km/h higher with the rear engine running than with the front engine (both were DB-603s with identical power rating). The pusher design is more efficient, because the suction forward of the prop reduces flow separation, and the accelerated flow behind it is not streaming around the fuselage (or wing), where it would create additional friction drag. Therefore the shaft of a jet engine is tension loaded, just like a propeller shaft in puller configuration. Even in a pure jet engine, a lot of thrust is generated by the compressor. In turbofan engines, most of the thrust is generated by the fan and compressor stages. Jet engines are by their very nature push-engines Wikipedia has a list of additional disadvantages. Since the propeller is behind the landing gear, it is susceptible to debris kicked up from the gear, increasing the need for added blade protection (increased weight, loss of efficiency) Therefore the diameter needs to be reduced (loss of efficiency) or the landing gear struts need to be made longer (added weight). The vibration makes the propeller blades more susceptible to metal fatigue.ĭue to the pitch up at take-off, the propeller gets close to the ground. These cycles create additional noise and lower the efficiency of the propeller. If the propeller is fitted behind a wing, each propeller blade is passing through the separated boundary flow twice each rotation. There are many disadvantages, they seem to outweigh the advantages.Ī pusher prop is working in a disturbed airflow, causing increased vibration and noise Velocity, Rutan), ultralights ( Quad City), military, or experimental. Single engine aircraft are even more uncommon, and pretty much all I could find except the Lake Buccaneer are all kit-planes (e.g. And the Cessna Skymaster is a push/pull configuration (If you get a multi-engine rating in a Skymaster, your ticket will be limited to multi-engine aircraft with in-line thrust). The Convair B36 is one notable multi-engine aircraft with engines in pusher configuration, as is the Piaggio Avanti. If there isn't an inherent disadvantage, why are pusher configurations so rare? If there is one, why do they exist at all? Disregarding designs where the choice is obvious, like powered parachutes where you simply don't want a propeller in your face. Twins generally have their engines on the wings, and the tail is no longer directly behind it, does that mean the choice of a pull-engine is not as advantageous? Is there an inherent advantage to using pull-propellers except for the increased airflow over the fuselage and tail (with its rudder and elevator)? Jet engines are by their very nature push-engines, however, most propeller airplanes use pull-engines.
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