Lots of fuel leaking below air intake on lower front cowl

[Nathan K. Hammond]

Don't worry Ron, were still cool.

nkh

[Nathan K. Hammond]

Doc, back to your question.... Head Pressure refers to the fuel pressure at the carb, on a carbureted engine. In the case of Aeronca's (and most other high wing, carbureted airplanes) there is no fuel pump, the whole system works on gravity. Here's the reader's digest condensed version without going into the physics of it all:

The fuel tank is located above the carb, so the fuel coming out of the line at the carb is under pressure because of the Potential Energy (Energy=Mass x Height). Because each airplane has it's own head pressure theoretically (M x H) you have to adjust the Seat height to prevent the carburetor bowl from over filling. In other words, the fuel pressure (head pressure) can create more force than the buoyancy of the float, and you adjust the Seat accordingly.

As for the proper head pressure when setting up a carb for a Champ... well I OBVIOUSLY don't know because my carb drips when the fuel is left on.

Here is a picture to help understand how a Carb works.

FYI: if your carb is dripping, it's because the Seat is at the incorrect location, which in turn, allows too much fuel in the bowl, which then becomes higher than then Nozzle, so the fuel flows out of the Nozzle.



nkh

[drskyking]

Thanks Ron. Again, mine doesn't leak a drop when off, only after running, last night after 2 hrs of flight, much less, but still some. Will let you know what I find!

[drskyking]

Nathan also, thanks for the info! Makes perfect sense, however, it doesn't leak when engine not running....Thanks for the diagram!