That rattle on a windy morning

[nosefirsteverytime]

Many times I've taken the scenic route from the car park to my company's lair in the Baggage Hall, and on the windier mornings, before many of the aircraft are on their way, you can hear this almighty rattling din coming from the engines.

Obviously it's from the fan blades, but what I'd like to know is there a sound reason why the blades are let run & rattle on the ramp like that?

[tom775257]

Simply the fan blades are loose without aerodynamic and centrifugal loading on them, so as they fall over the top they click.

At least on the aircraft I fly most (if not all)the noise seems to come from the front fan when windmilling

[pythagoras]

seems to happen more when they are cold - possibly due to being loose which allows room for expansion when the engine is running and they are hot.

[HarryMann]

I suppose the reason not to stop it, is jamming or clamping them would be far too prone to accidental foreign body ingestion (forgetfulness)...
It obviously doesn't do any harm to the blade roots... those are often fir-tree style blade roots flipping across