Learjet 60 - Engine Fuel and Control

Learjet 60
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Pilot's Manual
ENGINES
ENGINES & FUEL
The Learjet Model 60 is powered by two PW305A Pratt and Whitney
two-spool, front-fan engines . Each engine is rated at 4600 pounds
thrust at sea level .
A spinner and an axial-flow fan, located at the forward end of the en-
gine, are driven by the low-pressure rotor . The low-pressure rotor
consists of
an axial-flow fan (low-pressure compressor) and a three-
stage low-pressure axial turbine, mounted on a common shaft . The
high-pressure rotor consists of a high-pressure compressor
(four axial
stages and a single centrifugal stage) and a two-stage
high-pressure
axial turbine, mounted on a common shaft . The
rotor shafts are con-
centric, so that the low-pressure rotor shaft passes through the
high-
pressure
rotor shaft . The high-pressure rotor drives the
accessory
gearbox through a driveshaft geared to the N2
rotor shaft .
An annular duct serves to bypass
fan air for direct thrust and also di-
verts a portion of the fan air to the
high-pressure compressor . The by-
pass ratio (bypass flow to core flow) is 4
.55 : 1 . Air from the low-
pressure compressor flows through variable
inlet guide vanes and
first-stage variable stator vanes to the
high-pressure compressor and
is discharged into
the annular combustor . Combustion products
flow
through the high- and
low-pressure turbines and are discharged
ax-
ially through the exhaust duct to
provide additional thrust .
ENGINE FUEL AND CONTROL SYSTEM
The engine fuel and control system
pressurizes fuel routed to
the en-
gine from the aircraft fuel
system, meters fuel flow, and
delivers ato-
mized fuel to the
combustion section of the engine . The
system also
supplies high-pressure
motive-flow fuel to the aircraft fuel system for
jet pump
operation . The major components of the system
are the
thrust
levers, the engine-driven fuel pump, the
hydro-mechanical fuel
control
unit (HFCU), the full authority digital electronic
control (FA-
DEC),
variable inlet guide vanes, variable stator vanes, and
the surge
bleed control .
PM-123
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