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Propeller

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The Propeller (ella-ella-ay-ay)

(n.) Big wooden+ whirly thing. Makes planes and boats go forward.

+Except when they're made of metal. Or CFRP. Or some form of unobtainium.

Principles of operation

Tractor propellers

Propellers work by the principle of Conservation of Obstinacy (sometimes known as Kelvin's Law of Bloody-Mindedness):

  • The engine burns fuel and in doing so, gets hot. As any fule no, hot things want to cool down. And, again, as any fule no, there's nothing better for cooling down than having a nice cold beer.
  • Unfortunately for it, the engine is well aware of the fact that no self-respecting Pilot or Mechanic is going to waste beer on a lump of metal. So, it's mightily pissed off. It takes this frustration out on the big lump of wood/metal it's connected to, namely the prop.
  • Now, as anyone who has played Rugby will know, props are gay and can't handle the constant grief from the engine as well as requests for beer that it hasn't got either. Because of this, the prop gets into a "right old spin".
  • This spinning motion annoys the hell out of the air around it, and the air just gets out of the way as quickly as it can.
  • Most importantly, this then creates a vacuum in front of the plane. Nature, of course, abhors a vacuum and the plane obligingly steps into the breach.

Pusher propellers

In the case of pusher propellers the principles are slightly different in that the prop has convinced the engine that the beer is at the front of the plane (where the engine isn't).

The engine is therefore trying to shove its way to the front of the plane in a manly, heterosexual way (all engines are straight males, don't let Ducati enthusiasts try to convince you otherwise).

The prop still gets into a spin, but mostly because it's stuck to the back of a desperately over-excited engine.

Drawbacks

All that flapping about wastes a lot of energy, limits speed and let's be honest, looks shit, so most real planes these days have jet engines instead.