The engine on our single is Bendix fuel injected. It has a fuel pressure sender, which measures pressure, as well as a fuel flow sender, which measures flow. Yes, I know my fuel flow, and no, it's not just pressure expressed differently. The flow meter has been calibrated to be extremely accurate, so if it departs from its normal range we will notice very quickly.
The flow isn't tied directly to pressure, because the pump supplies more than the engine needs. Our fuel pressure goes up significantly when the boost pump is switched on, and so does the flow... briefly. Then the fuel servo adjusts to the new pressure, and the flow goes right back to where it was.
Sorry but do you know what you are talking about at all. Two different things
! fuel px is as it says, it measures pump px pre fcu. It leys you know if you have a edfp failure and allows you to turn your electric boost pump on which is required by certification to be able to run your engine to max power.
Now next.
The fuel flow is a px measuring gauge calibrated in fuel flow it is taken from the fcu. it is not part of the fuel px sysyem. it measures flow via px to the fuel nozzles. this is the same for both types of systems. now you also may have a digital flow vane which measures in units and not px but you will have the first system as it is mechanical and requires no power.
Now when you hit the boost pump this places more fuel to the fcu the fcu limits and bypasses the excess fuel. thus recreating the fuel balance to the engines requirements.
So may be you can explain how the Bendix RSA fuel servo and metering system works please.