I think I'm the one who started this boost pump discussion.  So this will be my last post.

 

We all learned way back when we took our private pilot written exam (hopefully) that there's a range of mixtures that can produce combustion.  Near the limits of that range your engine gets rough.  If you're out of that range it gets quiet.  If you are operating near the maximum rich mixture and you hit the high boost, you could create a mixture that won't produce combustion.  In cruise we are running close to stochimetric, either a little richer or a little leaner.  So our engines can handle the extra fuel flow caused by the high boost.  But on takeoff we are running quite a bit rich (several GPH) of stochimetric.

 

So it's reasonable to think that if an aircraft wasn't set up for proper fuel flow, and the fuel flow was high enough to start causing loss of power, that a pilot could interpret the rough running engine as a LOW fuel flow emergency and hit the high boost.  That would put him out of the "combustion range" of mixtures and the engine would quit.

 

Maybe someone knows how rich we can be before the engine starts running rough or quits, I'm curious.  I'm guessing there's a formula somewhere.

 

Mike Easley