Fuel System; General Description - Thrush Aircraft S2RHG-T65 TURBO THRUSH Maintenance Manual

THRUSH AIRCRAFT INC – MODEL S2RHG-T34 TURBO THRUSH
AIRCRAFT MAINTENANCE MANUAL

FUEL SYSTEM

GENERAL DESCRIPTION

(See Figure 5-1)
A 230 U.S. gallon fuel supply is available for the Turbo Thrush. In each wing, fuel is
contained inside integral wing tanks (wet wing fuel tanks) just outboard of the fuselage.
The left wing and right wing fuel tanks are interconnected through a 5 U.S. gallon header
tank that is located in the fuselage. The fuel supply lines, to the engine, are routed from
the header tank outlet finger screen through a fuel shutoff (on/off) valve to an electric
driven fuel boost pump. The electric driven fuel boost pump discharge is then routed
through a 25-micron main fuel filter to an engine driven fuel boost pump. The electric
driven fuel boost pump serves two purposes, first as a backup system to provide
continuous fuel pressure to the engines high pressure fuel pump in case the engine
driven fuel boost pump fails and secondly to provide boosted fuel pressure to the engines
high pressure fuel pump during engine starting. Fuel from the aircraft fuel system enters
the engines high pressure fuel pump which has two fuel filters, a 74-micron inlet filter and
a 10-micron discharge filter (Refer to the engine appropriate maintenance manual for
pertinent maintenance details for the engine supplied filters and fuel system).
The fuel tank vent system is designed to keep the fuel spillage to a minimum. The fuel
tanks are vented through tubing connected at both the inboard and outboard ends of the
individual fuel tanks to the centrally located vent system in the fuselage. Ram air enters a
vent scoop, on the fuselage under the left wing, and pressurizes the vent system to
maintain positive pressure on the fuel tanks. The vent system is provided with two quick
drains, located on the fuselage under each wing to drain any fuel that might happen to
have got in the tanks outboard vent lines.
At engine shutdown, fuel from the flow divider/dump valve, located at the 6 o'clock
position on the engines fuel nozzle manifold or start control unit on older engines
equipped with a start control unit, is directed to a residual fuel reservoir "EPA tank"
mounted inboard on the L/H aft shin skin. This reservoir holds approximately 3 engine
shutdowns worth of fuel before the fuel will exit the reservoirs' vent system. This reservoir
should be emptied after each shutdown. Also, it is common and normal after an engine
compressor Water Wash or Performance Recovery Wash to have water or soap appear
in the reservoirs' drained waste fuel.
The fuel quantity gauge is located on the lower left instrument panel. The fuel quantity
indicated system consists of two transmitters, one indicator gauge, and an L/H or R/H
tank fuel quantity selector switch. A transmitter, installed in each wing tank, transmits an
electrical signal to the single fuel quantity indicator. The instrument reads either the left or
right fuel tank individually, as chosen by the electrical control switch, adjacent to the fuel
quantity indicator gauge on the instrument panel.
The two fuel tanks are serviced through filler ports located on the top of both wings. The
filler ports incorporate security chains to prevent the loss of the fuel caps. Service the
aircraft from refueling facilities that utilize proper ground handling equipment and filter
systems to remove impurities and water accumulations from the bulk fuel. If filtering
facilities are not available, filter the fuel through a quality high-grade chamois. Fuel tanks
should be serviced after the last flight of each day to reduce condensation and allow any
entrapped water accumulations to settle to the fuel system drains. Prior to the next flight,
5-2
Effective: 9/16/05