An incident with a Rotax 912 ULS Bing carburetor
On turning on the fuel in my plane, even without the electric fuel pump on, fuel was pouring from the bottom of the motor enclosure, it was found that the co-pilots carburetor was literally pouring out of the bottom of the fuel bowl though a hole about 1mm in diameter.
On the removal of the bowl, it was found that the outer float was laying over in the bowl along with its holding pin.
On further testing, it was found that the fuel pump could keep the bowl full of fuel and the float working even though the fuel was pouring out of the hole in the bottom of the carburettor. The problem was fixed, but, is this a design fault? If the hole didn’t go right through the carburetor bowl and the same thing happened, then the fuel then would not have been able to escape and become a fire hazard. We were lucky it was found before flight.
I have a feeling that this has been happening for a while as sometimes when I did the pre-takeoff checks, I would wipe my finger under the co-pilots side carburettor and there was an orangey fuel stain, consequently, I have taken the bowl off to have a look at the bowl seal but only to find nothing obvious. The pin must have been loose but not loose enough to fall out of it’s mounting hole.