spirals

[BarnatosGhost]

quick one: what is the purpose of the spiral painted on the hub at the front of a jet engine?

[FourWheelDrift]

Hypnotises the runway into thinking the plane is taking off, we all know it needs a conveyor belt.

[navier_stokes]

1. So you know the fan is rotating.
2. To scare away birds.

There are obviously other better options for both of the above (e.g. engine noise is a more effective way of scaring birds away ), but those are the two actual reasons.

[Eric Mc]

Serious answer - it signifies to a ramp worker that the engine is operating. Workers often wear ear defenders. There is always a lot of extraneous noise out on the ramp so it's not obvious what particular engines are actually running.

Spirals were also used by the Luftwaffe on their fighters during WW2 - for the same reason.

[Simpo Two]

Eric Mc said:

Spirals were also used by the Luftwaffe on their fighters during WW2 - for the same reason.

And we had yellow tips on the propellers - as I remember well from many Airfix models!

[Eric Mc]

Simpo Two said:

Eric Mc said:

Spirals were also used by the Luftwaffe on their fighters during WW2 - for the same reason.

And we had yellow tips on the propellers - as I remember well from many Airfix models!

Which the Americans copied.

Prior to WW2, some USAAC and US Navy aircraft had red/yellow/blue tips.

In the 70s, an odd alternating black/white/black scheme was adopted by the RAF and showed up on their Chipmunks and Bulldogs,

[BarnatosGhost]

thanks chaps, suspected as much.