Diamond DA 42 NG, Maintenance Manual

Page: 977 / 2339

AIRCRAFT
DA 42 NG AMM Fuel
Doc # 7.02.15
Rev. 4
28-20-00
Page 3
15 Mar 2018
2. Description
A. Normal Operation
Figure 1 shows the schematic diagram of the fuel distribution system for the DA 42 NG airplane,
auxiliary tanks not installed. Figure 2 shows the schematic diagram with the auxiliary fuel tanks
installed. Figure 3 shows the items connecting the auxiliary fuel tank to the main fuel tank.
A flexible hose connects the main fuel tank outlet to the fuel transfer/shut-off valve. The fuel
transfer/shut-off valve is located in the related engine nacelle, aft of the engine firewall. A lever in
the cockpit center console controls the fuel transfer/shut-off valve via a mechanical drive system.
The fuel transfer/shut-off valve connects to the parallel installed independent pre-filters and the low
pressure fuel pumps. The electrically powered fuel pumps connect then to the fuel filter assembly.
A drain valve is located at the bottom of the fuel filter assembly. The bottom of the fuel filter
assembly forms the sediment trap.
The fuel filter assembly connects via flexible hose to a fuel bulkhead fitting on the engine firewall.
From there a flexible hose connects the bulkhead fitting to a fuel pressure pulsation damper and
then to the engine driven high pressure fuel pump.
A flexible hose connects the engine fuel system return line to the return bulkhead fitting located on
the engine firewall. A flexible fuel hose connects on the nacelle side to the return line of the fuel
transfer/shut-off valve. Another flexible hose connects the return of the fuel transfer/shut-off valve
to the related main fuel tank return system.
During normal operation the fuel returning from the left engine will flow through the left fuel cooler
back into the left fuel tank. Flexible hoses connect the fuel cooler into the fuel return system. The
fuel cooler is located in the rear of the engine nacelle. A NACA duct in the lower surface of the rear
engine nacelle supplies air for the fuel cooler. A shroud around the fuel cooler guides the air from
the NACA duct through the matrix of the fuel cooler. The air from the cooler exits from the nacelle
through air outlets at the rear of the nacelle.
If the optional auxiliary fuel tank is installed (OÄM 42-056), a flexible hose runs from the outlet of
the auxiliary fuel tank to the auxiliary fuel pump. Another flexible hose runs from the outlet of the
auxiliary fuel pump via an inline filter, a solenoid valve and a check valve to a T-fitting which feeds
the auxiliary fuel into the return fuel circuit.
The check valve and the solenoid valve prevent a backflow of the cooled return fuel from the engine
into the auxiliary fuel tank. To protect the solenoid valve from contamination an inline filter is
installed in the fuel transfer line directly at the outlet of the auxiliary fuel pump.