PRR A5 0-4-0

[Sumpter250]

So maybe I'm missing something obvious, but why is there the need to remove the spark arrestor in the first place - why can't it be permanently left in place (with of course a way to remove it when maintenance is being done)?

What reminds the crew to swing it into place and to remove it once the danger zone is passed? Wouldn't it be hot and heavy to handle?

I asked the same question, when I watched the fireman unbolting, and opening slightly, the spark arresting screen on the #5 Shay at Cass Scenic.
The answer: If the screen is left in place, it clogs with ash, and unburned coal, and sometime in the middle of the night, shuts off the draft, that keeps the fire burning in the firebox ( combustion requires fuel-heat-and oxygen -- draft --).
It's a long process to restart the fire and bring the boiler back up to pressure, so ---- the screen is removed, or at least opened some to allow the fire to "breathe", and just a few shovels full, of coal, brings the loco back to operation.

Puddlejumper, Many thanks for the great detail shots of the A5's. I wasn't able to find many.