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.
I would also know of an EDP failure by the sudden silence! To protect against that, during critical phases of flight (such as takeoff and landing), the boost pump is switched on. And lo, the fuel pressure rises, the flow also
briefly rises, and then returns to its original value. The behaviour is the same from idle to takeoff power.
This isn't theory. It's what actually happens in our aircraft... unless the gauges are participating in the same elaborate hoax.
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.
We do indeed have a fuel pressure gauge. Like the flow gauge, it's electric. Or did I merely imagine connecting the wires from it to the sender when I installed it?
Now, of course, I'm going to have to go back to the fuel system and remove the flow sender from its inline position before the FCU, where it measures nothing but flow through it, and tee it into the line from the flow divider along with the separate pressure sender. That will make it measure pressure all right, as flow sensors clearly should.
And we must have forgotten to install the return line too. Damn, I wonder where all that bypassed fuel has gone. But since our engine isn't a Continental, I'm fairly sure we got it right. And, also because it's not a Continental, the boost pump can be run at full pace as a backup without flooding the engine into spluttering submission.
I think Jaba pointed out that not all injection systems are the same. I won't presume to expound on how all of them work. But I do know a bit about ours...