Quote:
Originally Posted by JtD
I think you're looking at the fuel pressure gauge, and while I'm not sure how the Buffalo actually worked, it might be correct that the fuel pressure is related to manifold pressure.
The fuel quantity gauge is on the right side of the cockpit, and it does not move with the manifold pressure. I think it shows the contents.
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That's correct to a certain extent. At very low throttle settings the fuel pressure drops, but stabilizes to the correct value once above that threshold. Meaning, it's ok for fuel pressure to drop with low MP but moving the throttle forward just a bit should stablize it...it will then remain steady no matter the changes in throttle, as long as it is above that critical point.
It's usually why checklists state things like "idle at 1000 RPM", the closed throttle position actually gives lower RPM than that but fuel (and in some cases oil) pressure are too low for proper operation, plus the spark plugs can get dirty if running too low a MP setting for long.
That's also part of the reason real world pilots do an engine run-up prior to take-off...increasing throttle to check magneto RPM drops and exercise the propellers (moving the pitch lever back and forth to pump warm oil into the governor and ensure smooth pitch control) has the positive side effect that residue on the spark plugs gets burned off and they are clean and ready for take-off.