Learjet 60 - Auxiliary Power Unit (APD)

Pilot's Manual
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Learje 60
AUXILIARY POWER UNIT (APU)
The optional Auxiliary
Power
Unit
(APL), located in the rear equip-
ment bay,
is a self-contained, single stage gas turbine unit that can be
operated continuously up
to
an ambient temperature
of 130' F
(54' Q .
The APU provides electric power for ground operations of the aircraft
electrical system,
independent
of the aircraft main engines . It is restrict-
ed to ground operations only . The starting,
acceleration
and operation
of the engine is controlled byan integral system of automatic and coor-
dinated pneumatic and electromechanical controls
.
The AM engine is comprised of
three
major sections : the accessory sec-
tion, compressor section and turbine section . Engine power for the aux-
iliary power unit is developed through compression of ambient air by
a single entry,
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m- ,, radial, outward-flaw, centrifugal compressor . The com-
pressed air, when mixed with fuel and ignited, drives a radial inward-
flow turbine rotor .
The APU
control panel (located above the copilot's
circuit breaker
panel) contains all the primary controls to operate the APU . There is
also an APU
Relay Panel
and APU BITE (Built-In-Test-Equipment) box
(primarily for maintenance used, located in the APU compartment,
which displays the fault codes associated with the APU .
The engine is controlled and serviced by four systems : the engine fuel
system, lubrication system, electrical
system and
indicating system .
Fuel for the APU flows from the fuselage fuel tank on aircraft 60-001
tint 614072, or the left wing fuel tank on aircraft 60-073 and subsequent,
ough the APU boost pump, a shutoff valve and a fuel filter prior to
reaching
the AM The
APU uses
approximately 40 pounds of
fuel per
hour . Running out of fuel in the fuselage fuel tank or left wing fuel tank
will introduce air in the APU fuel lines which will cavitate the APU and
prevent it from restarting immediately, The APU gearbox serves as an
(A
sump far
the APU self-contained lubrication system
.
The
APU Elec-
tronic Sequence Unit (ESU) is a fully automatic system that directs de-
livery of the correct amount of fuel regardless of ambient conditions
and load requirements, as well as properly sequencing control of fuel
and ignition during starting
.
The ESU also monitors engine
parameters
during operation and automatically shuts down the APU in the event
a parameter is not within operational limits . A weight-on-wheels input
prevents operation of the APU while airborne .
Z44
PAT-a23
Change 4