Whoa... flashbacks. "Johnstown tower, Chautauqua 4204, braking action nil..."If you hear a TPE331 start up, after the engines get spooled, you'll hear a quick burst of reverse pitch. That backs the hub off the pins allowing them to retract, allowing the prop to coarsen the pitch.
But does a free power turbines compressor cool down and spool down with the prop in feather? I would think the compressor would run at the same speed and temp regardless since it is not connected to the prop. Am I thinking about this too hard?1. It allows it to cool down and spool down a bit before just being stopped abruptly
I understand that a feathered prop will slow down faster on shutdown, but why do they run the prop in feather for a prolonged period? The Dash for example runs in feather for about a minute before shutdown. I have never seen one shut down right away.
You are correct. You could leave a free power turbine engine in the feather condition until the cows come home.But does a free power turbines compressor cool down and spool down with the prop in feather? I would think the compressor would run at the same speed and temp regardless since it is not connected to the prop. Am I thinking about this too hard?
Short answer, that's because the checklists says props in fx minimum 30 seconds before selecting fuel off. The explanation they gave us is so that it will allow the engine and gearbox to cool down/stabilize before you shut it down. If it's run in feather any longer than 30 seconds, it's probably because we're using it for electricity/air conditioning until they get the ground services hooked up.I mostly see it on the dash, I see them a lot. They always feather for a prolonged period before shutdown.