Cessna 152 1979, Pilot Operating Handbook

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CESSNA SECTION 7
MODEL 152 AIRPLANE & SYSTEMS
DESCRIPTIONS
1 July 1978 7-21
Fuel flows by gravity from the two wing tanks to a fuel shutoff valve. With the valve in the ON
position, fuel flows through a strainer to the carburetor. From the carburetor, mixed fuel and
air flows to the cylinders through intake manifold tubes. The manual primer draws its fuel from
the fuel strainer and injects it into the cylinder intake ports.
Fuel system venting is essential to system operation. Blockage of the venting system will
result in a decreasing fuel flow and eventual engine stoppage. Venting is accomplished by an
interconnecting line from the right fuel tank to the left tank. The left tank is vented overboard
through a vent line which is equipped with a check valve, and protrudes from the bottom
surface of the left wing near the wing strut attach point. The right fuel tank filler cap is also
vented.
Fuel quantity is measured by two float-type fuel quantity transmitters (one in each tank) and
indicated by two electrically-operated fuel quantity indicators on the lower left portion of the
instrument panel. An empty tank is indicated by a red line and the letter E. When an indicator
shows an empty tank, approximately.75 gallon remains in either a standard or long range tank
as unusable fuel. The indicators cannot be relied upon for accurate readings during skids,
slips, or unusual attitudes.
The amount of unusable fuel is relatively small due to the dual outlets at each tank. The
maximum unusable fuel quantity, as determined from the most critical flight condition, is about
1.5 gallons total. This quantity was not exceeded by any other reasonable flight condition,
including prolonged 30 second full-rudder sideslips in the landing configuration. Takeoffs have
not been demonstrated with less than 2 gallons total fuel (1 gallon per tank).
The fuel system is equipped with drain valves to provide a means for the examination of fuel in
the system for contamination and grade. The system should be examined before the first flight
of every day and after each refueling, by using the sampler cup provided to drain fuel from the
wing tank sumps, and by utilizing the fuel strainer drain under an access panel on the right
side of the engine cowling. The fuel tanks should be filled after each flight to prevent
condensation.
When the airplane is equipped with long range tanks, it may be serviced to a reduced fuel
capacity to permit heavier cabin loadings. This is accomplished by filling each tank to the
bottom of the indicator on the fuel filler neck. When filled to this level, the tank contains 13
gallons ( 12.25 usable in all flight conditions)