Learjet 60 - Fuel Control Unit; Fuel Pump; Thrust Levers

Learjet 60

Pilot's Manual
THRUST
LEVERS
Two thrust levers (one
for each engine) are located on the upper
por-
tion of the pedestal, and
operate in a conventional manner
with the
full forward position being
maximum thrust . Stops at the IDLE posi-
tion prevent inadvertent reduction of
the thrust levers to CUT-OFF .
The IDLE stops can be released by
lifting a finger lift on the outboard
side of each thrust lever . Detents
are provided for CUT-OFF, IDLE,
maximum cruise (MCR), maximum
continuous thrust (MCT), takeoff
(TO),
and automatic performance reserve
(APR) . Each thrust lever is
mechanically linked to a rotary
variable differential
transformer
(RVDT)
position transducer . The RVDT
provides dual electrical sig-
nals to the
FADEC which correspond to the
thrust lever angle (TLA) .
A switch, which
actuates in the CUT-OFF
position, provides a dis-
crete signal to the
FADEC to initiate the normal
shutdown sequence .
ENGINE-DRIVEN
FUEL PUMP
The engine-driven fuel
pump provides high-pressure
fuel to the en-
gine fuel control system
as well as motive-flow
fuel for operation of
the aircraft jet pumps .
The pump consists of a
low-pressure pump ele-
ment, high-pressure
pump element, relief valve,
and motive flow pro-
visions .
The pump itself is housed in the
hydro-mechanical fuel con-
trol unit . Fuel
from the low-pressure
element passes through
a filter
before it
enters the high-pressure
element . In the event
the pressure
differential
across the fuel filter
increases to a preset
level, the im-
pending bypass
indicator will actuate
and the white ENG
FILTERS
light
will illuminate . If the pressure
differential continues to
increase,
due to clogging, the filter bypass
valve will open to allow
fuel to by-
pass
the filter .
HYDRO-MECHANICAL FUEL
CONTROL UNIT
The
hydro-mechanical fuel
control unit (HFCU) mounts to the
perma-
nent magnet alternator on the aft
side of the accessory
gearbox . The
HFCU's
main function is to control
fuel flow to the engine's fuel
noz-
zles .
Fuel flow is regulated in response
to commands from
the FA-
DEC which computes the necessary
settings for the existing
condi-
tions .
The HFCU also provides
servo pressure to the variable
guide
vane
actuator, houses the engine-driven
fuel pump, and provides
fuel
pressure
regulation .
PM-123

2-3
Original