The problem with pushers

The pusher propellor configuration has always played second fiddle to the more traditional ‘tractor’ configuration in light aviation, but why is that so?

The main reasons are a combination of negatives, associated with the environment that most pusher propellors are forced to work in, which end up outweighing the positives.

With a single engine/prop configuration the pusher is typically being driven directly off an internal combustion reciprocating engine. This forces the layout of the prop having to be positioned at the back of the fuselage and therefore working in ‘dirty’ air, which makes it inefficient and noisy in operation.

Also due to its position at the back of the fuselage the prop has to be of a small diameter to allow good ground clearance when the aircraft rotates for takeoff and is flaring for landing. Because of this forced reduction in diameter the prop is less efficient and typically has to have more blades, increasing cost.

Finally the prop has to deal with FOD (Foreign Object Damage), from the undercarriage tyres, flicking up stones and other debris into the propellor arc. Pusher props have a hard life and don’t last as long as tractor props due to this constant FOD problem.

With the Bluebird it’s multiple electric propulsion motors free us from the negatives of the traditional pusher layout, allowing us to position the props out of the fuselages ‘dirty’ air and away from the nose wheels FOD arc. This eliminates two of the previous negatives of the pusher layout. Also by the use of multiple propellors this allows for a large increase in propellor efficiency, the principle being to shift a larger volume of air with less change in it’s velocity, which equals greater efficiency. Due to their constant torque output, electric motors allow the props to run at a much lower rpm than usual, around 1,700 rpm as opposed to the usual 2,700 rpm.

The Bluebird therefore employs a quieter, more efficient and longer lasting pusher solution with all the positives of laminar flow air on the fuselage and wing root area and none of the negatives of the traditional pusher or tractor layouts.

The Velocity XL - a traditional pusher layout with all the negatives of just such a layout.