It refers to the plume of steam from the safety valves when the boiler pressure is high.
If you’re showing a white feather, it means that there is steam coming from the safety valve(s) on a steam locomotive.
Of course, this is indicative of high boiler pressure.
Andre
I agree.
[#ditto]
[#ditto][#ditto]
Actually, the white feather is that little stream of steam that shows just before the safeties lift and lose you a dozen pounds of steam pressure, so, for the fireman, trying to keep the pressure right there is sort of like trying to balance on a tightrope.
Chuck
Yep.