Originally Posted by
Gaspar
Hi,
I see that there are some misunderstandings about what the ecu does, the ecu don't shutdown the engine in the case of a clogged filter.
-If the RPM of the engine don't reach the commanded value, the ecu increases the pump power up to the "pump limit" value, not more. It doesn't shutdown the engine, just sits there so that the engine continue running at reduced power, issuing the alarm "Pump Limit reached" that you can see after the flight.
-Sometimes the engine flame out because when returning to idle, the calibrated power for the pump at idle (calibrated at each startup) is not in aft to keep the engine running. Other reason is that the fine bubbles caused by the cavitation in the aspiration line colapse to big bubbles when the power is retarded, due to the less fuel demand, causing the combustion to cease.
-In the case of overspeed the ecu don't shut down the pump, it just reduces the fuel flow very fast to fet the speed back to the safe zone. Some engines flame out due at too fast fuel reduction, but this case is not usual in the engines I have tested.
Gaspar
Gaspar one thing I have seen is even with a pump limit of say 350 on a flameout caused by air the PW at engine shut down will go well over the pump limit reaching over 500 easy. So why does the pump PW overshoot the max pump limit set in the ECU?
I have also seen problems in the fuel system and the engine will do exactly like you say reach the pump limit and sit their then give you PUMP LIMIT REACHED on the data terminal. Sometimes I have seen this caused by the pump other times it was other fuel system problems.