North Wing S-LSA Maintenance Manual
Model: Scout 912
Version 3.2
Release date 04-16-2014
Page 56
4.4 Fuel System Repairs
The fuel system schematic is shown below. The fuel tank is about a 17 gallon polypropylene
tank designed to straddle the root tube. An aircraft style drain valve allows removal of a
sample of fuel to assure no water is present in the tank. An equalizer line, located slightly
above the bottom of the tank to avoid picking up contaminants, gradually balances the level of
fuel in the left and right halves. The fuel supply to the engine is taken from the equalizer line
with a tee in the line.
From the equalizer line, the fuel flows to the electric fuel pump which is controller manually
from the switch on the instrument panel. The electric fuel pump can be used in case of a
failure of the mechanical fuel pump, and it can be used to prime the carburetors after sitting
dormant for several days. It is not intended for continuous use when the engine driven fuel
pump is working as designed.
A fuel pressure regulator was used on some units with the earlier Rotax 912 engine. After
Rotax added a fuel pressure regulator in the carburetor crossover line, this external regulator
became unnecessary. Your unit may or may not have a pressure regulator. If so, the fuel
pressure to the engine is limited by the regulator to 4.5 psi. This only comes into play when
the electric fuel pump is being used to avoid damage to the mechanical fuel pump on older
Rotax 912 engines. Under normal conditions, the electric fuel pump would be off and the
pressure at that point in the line would be less than atmospheric because the mechanical pump
would be drawing fuel up the fuel line.
The fuel pump is driven by the crankshaft eccentric on the Rotax 912 engine. The pump has
one outlet that feeds into the fuel manifold then to each carburetor.
The fuel lines are
¼
” alcohol resistant urethane tubing with clamps or wire wraps at both ends.
Not typically on
units after 2011