Volmer Jensen VJ-21

Tractor & Pusher Airplanes

A Pusher type installation

As you look at the VJ-21 hanging in the museum you may have noticed that the placement of the engine on the aircraft is a bit different than most airplanes that are here in the museum. This engine installation and location is known as a “pusher” airplane.

The other engine installation that is common on aircraft is known as a “tractor” type.

A Tractor type installation

Depending upon specific design, a tractor type can deliver about 92% of the engine power into usable thrust for the airplane. A pusher is somewhat affected by the airflow being disturbed by the parts of the airplane forward of the engine/propeller installation which decreases its efficiency to about 87%. Both types of installations offer some positive and some negative attributes about the particular choice of installation.

Many early aircraft were “pushers,” such as the Wright Flyer and the Santos-Dumont 14 bis. A number of military pilot fatalities in the early years involved pusher type aircraft resulting in them being looked upon as inferior to the tractor type. Pushers were an advantage for forward-firing guns as there was no obstruction from the arc of the propeller. Additionally, if a pilot had to parachute out of a pusher there was the possibility of passing through the propeller arc.

Some advantages of tractor type installations:

-In a crash, the tractor engine can absorb much of the impact.

-Tends to reduce propeller damage from debris thrown up by aircraft wheels.

-Lower propeller noise due to the airflow contacting the propeller being undisturbed.