Avro 504K (Original)

The Shuttleworth Collection 2016.

For those not used to seeing older machines such as this in flight, the smoke from the engine is nothing out of the ordinary and certainly nothing to be concerned by. Though this may look to many as having a radial type engine, it is in fact an early aero engine type known as a Rotary. These engines differ from radials in the fact that the entire crank case and it's cylinders rotated around a stationary crank shaft rather than the other way round, the prop turning with the crank case. If you look closely at the engine, it is possible to see the engine rotating with the propeller.

Many of these rotary types did not use a conventional throttle but utilised what was known as a blip switch to slow the aircraft. This was essentially a switch that would cut in and out the engine when used. The switch is most often utilised on landing as the pilot blips the engine on and off to keep the aircraft at the required speed for landing. These rotaries also injected castor oil into the fuel mixture as a way to lubricate the engine. The smoke seen in this photograph has been caused by the use of the blip switch, as when the engine cuts back in, a puff of smoke from the burning castor oil is released in the exhaust gasses.