CFItillIdie

Ok folks...I am trying to get some out of the box thinking here. And maybe a little words from people who have had experience with this first hand!

I personally have learned and the way that I understand aircraft systems to work is this...in the event of an engine driven fuel pump failure in a low wing aircraft FUEL INJECTED ENGINE, where the engine will quit and the emergency procedure to follow is the ABC's of that procedure. Now for the restart the electric boost pump is in every checklist that I have ever seen, however my REAL question is...Will it work? Does the engine roar back to life once you put that magical switch to the boost or on position? Are there any aircraft designed where the boost pump is not strong enough to restart the engine? Common sense would say no, but there might be some models out there that might have a subpar electric pump. Please any experiences would be appreciated!

PFactor

Hey CFItillIDie,

How long have you been a CSIP and what airport do you fly out of. I left the airlines to be at home as a CSIP. Really enjoy flying the Cirrus and other high-performance GA birds. Cirrus says if you experience an engine driven pump failure the boost pump will not provide enough pressure to continue to run the engine.

Have you ever had a student shut the plane down and leave the boost pump on? I'm certain it would not create enough power for sustained flight, but I believe the engine would still be "operating" or turning over. The 4-6psi of fuel pressure just is not enough to create the power required to continue flight. That design is really for vapor suppression.

rickair7777

TYPICALLY for all piston engines (for specifics see your airplane's AFM)...

Carbs: The boost pump and/or gravity supplies fuel to the carb. All you're doing is filling the float bowl at near-ambient pressure.

On a low-wing you need the pump, on a high-wing gravity alone is usually enough. The boost pump on a high wing is a back up to gravity...ie not strictly required unless you fly with sustained low g's, have some kind of flow resistance in the lines/filter to the carb, or experience a total gravity failure.

On some high wings gravity might not provide enough flow through the filter for sustained high-power ops (ie takeoff)...in which case boost pump use is mandatory.



Fuel Injection:The boost pump and/or gravity delivers fuel from the tanks to the inlet of the main fuel pump which requires a slight positive pressure head. The main pump boosts that pressure much higher, probably to about 30-50 psi for the injectors.

A failed boost pump may not stop the engine, but a failed main pump will. The boost pumps or gravity cannot supply more than 2-3 psi, nowhere near the 30-ish required for fuel injectors.

Again, read for AFM.