ENGINE RPM
Engine rpm is supplied from an engine-driven
tach generator mounted on the rear of each en-
gine-driven oil pump and driven by a com-
mon shaft. Dial markings are based on percent
of maximum allowable engine speed. The large
dial is graduated in 2% increments from 0 to
100%; the small dial is graduated in 1% incre-
ments from 0 to 10%. Engine rpm of 100%
e q u a l s a p p r o x i m a t e l y 1 6 , 5 0 0 r p m . T h e
tachometer system uses self-generated elec-
trical power from the tach generator.
FUEL FLOW
Fuel flow is measured by a transmitter on the
metered fuel line to the combustion section.
Fuel flow is indicated on a single-needle gage
and uses DC power. A two-position L–R switch
located below the gage provides for selection
of fuel flow indication for the left or right en-
gine. Models 24-354 and subsequent and 25-231
and subsequent have dual-needle gages installed.
OIL PRESSURE
The oil pressure indicating system consists of
an oil pressure transmitter and a pressure switch
installed on the engine nacelle bulkhead, and
a dual needle oil pressure gage.
One red low oil pressure warning light (see
“Annunciator Panel” section) is installed on the
glareshield. If the oil pressure drops below 5 psi,
the red low oil pressure light will illuminate. The
light uses 28 VDC, and the gage uses 26 VAC.
NOTE
There is one light for both engines;
therefore, if only one engine is op-
erating, the red low oil pressure light
will be illuminated.
OIL TEMPERATURE
Two oil temperature indicators powered by 28
VDC are installed in the instrument cluster on the
switch panel, and a probe is installed in the bot-
tom of each oil tank.
ENGINE STARTING
Moving the starter-generator switch to the START
position applies power to close the respective
motive flow control valve and energize the standby
fuel pump. With the motive flow control valve
closed, the starter relay is energized to apply power
to the starter. At 10% engine rpm, the thrust lever is
moved to IDLE, energizing the ignition and sup-
plying fuel to the fuel nozzles. When the engine
reaches an idle rpm of 48%, the starter-generator
switch is moved to GEN. This deenergizes the
starter relay, opens the motive flow control valve,
turns off the standby pump and ignition, and ener-
gizes the generator relays. The generator fail light
extinguishes, and the generator supplies power to
the airplane electrical system.
ENGINE
SYNCHRONIZING
WOODWARD ELECTRONIC
SYNCHRONIZER (OPTIONAL)
The engine synchronizing system consists of
a magnetic pickup in each engine overspeed
governor, a control box, throttle cable actu-
ator, control switch (Figure 7-14), and indi-
cator light (see “Annunciator Panel” section).
7-17
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
Figure 7-14. ENG SYNC Switch