Leerjet 35/36 Developed for Training Purposes 4K-7
February 1998
Powerplant
Fuel Control System
The fuel system consists of:
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fuel pump assembly
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hydro mechanical fuel control
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electronic fuel computer
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fuel flow divider assembly
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fuel atomizers.
Fuel is pumped by the engine fuel pump, filtered by the fuel fil-
ter, metered by the hydro mechanical fuel control in conjunction
with the fuel computer, delivered by the fuel manifold, and
atomized by the fuel nozzles.
The two-stage fuel pump contains a filter element and a filter
bypass valve. If the filter becomes blocked and a bypass
occurs, a red indicator pin on the pump housing pops out.
The fuel computer provides the following functions:
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start scheduling
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fuel scheduling
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ultimate overspeed protection
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surge valve control.
SPR (manual fuel enrichment) is a function of the fuel computer
and is controlled by the SPR switch labeled Land R. It is not
available if the computer is in manual mode or is turned off.
Although SPR is not required for normal starts, it should be
used for starts at temperatures below 0×F and during airstarts.
The SPR switch must be released when the engine ITT
reaches 400×C.
The fuel control unit modulates the metering valve to limit
engine RPM to 105%. The fuel computer provides ultimate
overspeed protection; if N
1 exceeds 109% or N2 exceeds
110%, the fuel computer energizes the ultimate overspeed
solenoid valve to shut off the fuel.
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