This was ignored on the Maule forum... or stumped em... Why do carbureted Maules have an engine driven fuel pump? Do other back country high wing planes have fuel (not boost) pumps?? Most high wing planes don't have them since they don't need the engine to drive fuel supply to a carb. What's going on?

Hi Spinner

I replied on the Maule forum.

Gene

Spinner

I can not speak specifically to the M@#$e. But the usual reason has to do with "head pressure" in the fuel line. Basically they are insinuating that if you do a maximum performance take off it is possible / probable to get the carburetor above the fuel - ergo - ZERO fuel pressure between the tank and the carb. Something like that.

That is sort of the way Harry Delicker of Delair in Porteville Calif. explained it to me.
Similar to some of the older Cessna 100 series that have the RED zone in the last quarter tank.
You can fly straight and level and descend in the red zone, but a take off would allegedly leave one with less than adequate fuel pressure.

Fortunately with my 180hp conversion I can take off with 20* flaps and the wing stays mostly flat.
Still it does have both a mechanical and a boost pump. Never use the boos pump - yet - but glad it is there.

There should be more and better explanations than just mine on this forum.

Hope that helps

Chris C

Maule uses a fuel accomulator tank outside the pilot's lower kick panel. It is normally under full gravity pressure from the tanks when full. If a tank is run dry and the accomulator tank is not full there will not be sufficient pressure to feed the carburetor.



Gene

My 175 O-360 constant speed will climb nose high enough to run out of fuel with just gravity. It has an engine driven and boost pump. Placard to use boost pump on take off and landing. Gravity will not do. Maule should be even better climb angle. Maybe not the answer but something the lawyers made happen.ML

The way it was explained to me that the FAA requires the gravity fuel flow rate to be 150% of what the engine will use at full power. If the fuel system cannot deliver this flow rate, presumably at any fuel level (full or empty), an engine driven fuel pump is required. And in case of failure of that fuel pump, a boost pump is therefor also required. I was told that the fuel line size was the limiting factor in the C150/150 & C170/180 conversions. Maybe it's easier to just add the fuel & boost pumps than to re-plumb with bigger fuel lines- esp if the fuel tank outlets would need to be enlarged also.