Aircraft propellers can be classified according to their position relative to the engine and airframe. The two primary configurations are tractor and pusher propellers. Each arrangement affects airflow, efficiency, maintenance requirements, and susceptibility to foreign object damage.
Tractor Propeller
Tractor propellers are those mounted on the upstream end of a drive shaft in front of the supporting structure. Most aircraft are equipped with this type of propeller. Tractor propellers are available in both fixed-pitch and variable-pitch configurations. A major advantage of the tractor propeller is that it operates in relatively undisturbed airflow, resulting in lower stresses on the propeller.
Pusher Propellers
Pusher propellers are those mounted on the downstream end of a drive shaft behind the supporting structure. Pusher propellers are constructed as fixed- or variable-pitch propellers. Seaplanes and amphibious aircraft have historically used pusher propellers more frequently than other types of aircraft.
On land aircraft, where propeller-to-ground clearance usually is less than propeller-to-water clearance of watercraft, pusher propellers are subject to more damage than tractor propellers. Rocks, gravel, and small objects dislodged by the wheels are quite often thrown or drawn into a pusher propeller.
Similarly, aircraft with pusher propellers are apt to encounter propeller damage from water spray thrown up by the hull during landing or takeoff airspeed. Consequently, many pusher-propeller installations are mounted above and behind the wings or fuselage to reduce the risk of such damage.
| Tractor vs. Pusher Propeller | ||
|---|---|---|
| Feature | Tractor Propeller | Pusher Propeller |
| Location | Mounted in front of the aircraft structure | Mounted behind the aircraft structure |
| Airflow | Operates in relatively undisturbed airflow | Operates in airflow affected by the aircraft structure |
| Blade Stress | Generally subjected to lower aerodynamic stresses | May experience increased aerodynamic disturbances |
| Foreign Object Damage Risk | Lower | Higher |
| Maintenance Considerations | Typically less susceptible to debris and spray damage | More susceptible to debris and spray damage |
| Common Applications | Most conventional aircraft | Some seaplanes, amphibians, canard aircraft, and UAVs |
| Propeller Configurations | Available in fixed-pitch and variable-pitch designs | Available in fixed-pitch and variable-pitch designs |
Comparison of tractor and pusher propeller configurations.
