King Air PT6A-20 Fuel Control Unit & The P3 valve

moxiepilot

Well-Known Member
I need some help learning about this engine used on the King Air 90 regarding the Fuel Control Unit...

It appears that the computing section uses P3 bleed air to affect the evacuated bellows which would affect the metered fuel pressure, but I don't understand how or why pressurized air is used to meter the fuel flow.

Can anyone explain it in some less than technical terms?
 
I don't know anything about this engine, but I won't let that stop me from tossing out an answer ahead of someone who does...

P3 is the compressor exhaust, specifically the gas generator exhaust. So, making some assumptions about temperature, that should give the controller a decent indication of the airmass flow going into the combustor.
 
Minuteman, you're pretty good....but it's called "compressor discharge"...you're making me cringe... /ubbthreads/images/graemlins/grin.gif

Basically, Minuteman is hitting it. In an effort to schedule fuel flow at an optimum rate, the fuel control will use compressor discharge pressure (and temp, in some engines) to help.
 
Basically, Minuteman is hitting it. In an effort to schedule fuel flow at an optimum rate, the fuel control will use compressor discharge pressure (and temp, in some engines) to help.

[/ QUOTE ]

Thank you.
 
Back
Top