Hey everyone Another question, as always! You guys teach me so much - thank you,


so your flying a carbureted engine aircraft and the aircraft is put in a condition that creates Nagative G's where you see your papers and in some cases your poor dog flying around in the back seat!,

my question is while that is happening for about 2-5 seconds - would your carbureted engine quit?

or does the Engine Driven Fuel pump drive the fuel, does a carburetor engine even have a engine drive fuel pump!? other than auxiilery hmmm that's two questions in one!


thanks!

As far as I understand it, engines with float type carburetors will fail during negative g operations because the float itself requires gravity to function and maintain a constant level of fuel in the body. Pressure carburetors solve this problem by putting the fuel under positive pressure to ensure delivery.

Well...if it's got something that's called "Auxiliary", it MUST have something called "Primary". Don't you think?. In piston (carbureted) engines, the "primary" fuel pump, is the engine driven pump. And that pump has little to do with the negative G issue, since the fuel pumps (doesn't matter if it is primary or auxilary) drives the fuel to the carb. The engine would quit (in a float-type carb, which is not approved for aerobatic flight), because there's little or no fuel in the fuel chamber in the proper "position" to feed the engine.

Ed

Back in ww2 all american fighters had pressurised carbs

Thanks Gentlemen Appreciate it ;)

The engine does not quit in 2-5 seconds. My son got air..he loved it.. I didn't. Not something to practice just for whoo haas.

Hey Becky, Your probably flying around in a Fuel Injected C172, we're talking about something a little different!

Unless your not and you are talkinga bout what we are then that's great thanks

Fuel injected 152? The injection system would be more valuable than the airframe, but I digress. Two seconds of zero or low negative g, almost certainly no problem. Five seconds of negative g (say 1/2 or more) and I'm sure that you'll hear less noise. And it's fuel metering we are talking about, not pressure. Find out what the float chamber (in the carburettor) does and you'll be able to answer your own question.

PM

Thanks for the advice Pitdown, I should do that, it's on my list of things to read and understand along with many others!!

Ah, PM, how Ive missed you over these last few quiet months

I just found an article here in english that keeps it very simple and sums it all up (enginewise):
http://www.airborne-aviation.com.au/resour...tips/0510a.html

Chill

If there is enough pressure generated by your fuel pump(s) your float type carburator will continue supplying enough mixture for the engine to bang bang. I very much doubt that the standard issue civilian "week-end puddle jumper" piper or cessna could deliver, they where NOT built or certified for this condition.
On a side note, I would be more concerned about fuel starvation within the tanks as your maneuver makes your precious go-juice float away from the fuel intakes. Again the Piper/Cessna civilian kind where not designed with "acceleration following" fuel intakes. How about them apples?
It only takes 8 to 10 spins in a 150 to starve the engine as the fuel is pushed away from the fuel intakes to the wing tips. That is 10-20 seconds to watch the prop go horizontal, and good luck restarting a completely starved engine. I suppose a prolonged negative acceleration would prove to be just as dramatic.
Of course dramatic is relative to the amount of altitude you have to roll yourself a cigarette, light it up, prime the engine, set the mixture, and crank the starter bloc; while applying enough dynamic airflow to help rotate your little airscrew back to life. We might even be high enough that we just shock cooled the engine into spitting it's rings, sleeves, pistons out for inspection, through that crack that appeared.

Let me answer that based on experience: It will definitely sputter for a moment in time...and so will your heart!