PART 1-DESCRIPTIVE
(ii) The fuel from all the permanent tanks passes to a col-
lector box which also acts as a negative "g" reservoir
and incorporates negative "g" valves affording a fuel
supply for ten seconds inverted flight. The tanks, which
are not pressurised, are vented to atmosphere. A satis-
factory delivery pressure at altitude is ensured by a
booster pump, which is immersed in the fuselage tank.
(iii)The flow of fuel from the wing tanks to the fuse-
lage tank is controlled by a float valve mounted at the
top of the fuselage tank. The wing drop tanks are pres-
surised from the engine blower casing. Mod. 591 incor-
porates a reducing valve from each wing drop tank, thus
ensuring that fuel can be drawn from one tank should the
other be holed.
(iv) Fuel from the booster pump passes through a low pressure
cock and a filter, to an engine-drive pump capable of
maintaining a constant fuel pressure throughout the
power range. An aneroid-operated barostat, fitted to the
delivery line of this pump, controls the fuel supply by
returning surplus fuel to the collector box as height is
gained. The engine r.p.m. therefore remain substantially
constant at any selected throttle opening. From the
engine-driven pump fuel passes to the throttle (fuel con-
trol valve) and the high pressure cock. A minimum pres-
sure valve is fitted in parallel with the throttle. This
ensures that at altitude, regardless of the throttle setting,
sufficient pressure will be maintained at the burner ring
to prevent flame extinction, providing the booster pump
is ON. Maximum pressure at the burner ring is con-
trolled by an overspeed governor. From the overspeed
governor fuel passes to the starter valve, and the line is
tapped to supply a fuel accumulator. The purpose of the
accumulator is to provide a fixed quantity of fuel at a
known pressure at the moment of starting. When starting
the engine, a dump valve drains any fuel present in the
system, before the pressure builds up; when shutting
down the engine it prevents free fuel draining into the
combustion chambers after the pressure has fallen.
2. Fuel contents gauges
(i) Contents gauges
Five fuel contents gauges (38) are mounted below the
centre instrument panel. The top left- and right-hand
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