POWERPLANT
AIRPLANE
OPERATIONS
MANUAL
2-10-10
Page
2
Code
01
DECEMBER 20, 2002
The fuel-metering valve is controlled by the FADEC and controls fuel
distribution from the gear pump to the engine fuel nozzles.
Downstream of the metering valve, a pressurizing valve (PRV)
generates adequate system pressure for the proper functioning of the
main metering valve and pressure drop servos and CVG hydraulic
actuator. The PRV also provides the primary means for engine fuel
shutoff, commanded through the Latching Shutoff Valve, that receives
a Stop input from the cockpit through the FADEC.
FUEL-COOLED OIL COOLER (FCOC)
The FCOC is installed externally on the bottom of the outer bypass
duct, aft region. Fuel flows from the FPMU’s centrifugal pump to the
FCOC where it simultaneously cools the engine’s lubrication oil and
warms the fuel. A thermal/pressure bypass valve bypasses oil flow to
prevent fuel leaving the FCOC from being heated above 93.3°C
(200°F). The oil is also bypassed if the differential oil pressure is
greater than 50 psi due to hung or cold starts. After the FCOC, the fuel
goes to the filter.
COMPRESSOR VARIABLE GEOMETRY (CVG)
ACTUATION SYSTEM
The high-pressure compressor has a variable geometry vane system
on its five stages to provide maximum engine performance over a wide
range of engine speeds. The FADEC contains a schedule of vane
positions versus corrected gas generator speed (N2) that has been
selected to provide the optimum compressor efficiency of steady-state
conditions and adequate stall margins during transients.
The FADEC senses the vane position and, by means of fuel pressure
from the FPMU, commands the CVG actuator movement to position
the compressor-inlet guide vanes and the first five rows of compressor
vanes to the desired setting.
FUEL NOZZLES
Each engine has 16 fuel nozzles, that furnish atomized fuel to the
combustor at the proper spray angle and pattern, for varying airflow
conditions.
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