Changing the barometric scale from in. Hg to
Hpa:
• Depress and hold the barometric knob
for more than 4 seconds, but less than 8
seconds. Each depression will toggle
the baro scale between in. Hg and Hpa.
Changing the altitude readout from feet to
meters:
• Depress the barometric knob for more
than 8 seconds. Each depression will
toggle the altitude readout between feet
and meters.
NOTE
When returning from Hpa/meters to
in.Hg/feet, depress the barometric
knob for more than 8 seconds to
change altitude readout from meters
to feet. Depress the barometric knob
a second time for more than 4 sec-
onds, but less than 8 seconds, to re-
turn the barometric scale from Hpa
to in. Hg.
• Set the barometric pressure by
turning the barometric knob on
each ADDU. Momentarily press-
ing the barometric knob will set
29.92 in. Hg (1,013 Hpa).
NOTE
The master and slave barometric set
knobs are totally independent and
different units. Barometric settings
are possible between the pilot and
copilot ADDUs.
• Both ADDUs must be selected to
the same units (feet or meters) or
the altitude preselect function will
o n l y o p e r a t e f r o m t h e m a s t e r
ADDU.
The altitude position correction—Flaps (0°),
gear up, pilot and copilot ADDU charts in the
“Performance” section of the AFM Supplement
only applies when the STBY annunciator is il-
luminated on the ADDU display. Under nor-
mal conditions, the corrections are negligible.
The pilot and copilot altitude position correc-
tion charts in the AFM Supplement are to be ap-
plied under all applicable flight conditions.
Altitude Reporting
Altitude reporting may be supplied from ei-
ther ADDU. Selecting ADC1 provides alti-
tude information from the pilot ADDU for
either transponder. Selecting ADC2 provides
altitude information from the copilot ADDU
for either transponder. The TFR 1–2 transfer
switch is on the transponder control panel.
Selecting TFR1 transmits altitude informa-
tion from the LH transponder supplied by the
selected ADDU. Selecting TFR2 transmits al-
titude information from the RH transponder
supplied by the selected ADDU.
Autopilot Interface
Either ADDU may be used to supply inputs to
the AIU and hence the autopilot. Selecting
ADC1 uses the pilot ADDU as the air data source
for the AIU. Selecting ADC2 uses the copilot
ADDU as the air data source for the AIU. The
selected ADDU will have the active master in-
dicator “A” illuminated and will be the unit
used for transponder, autopilot air data input,
and other auxiliary inputs (Figure 16-15).
Altitude Alerter
Select the desired alerter altitude by rotating
the ALT SEL knob (Figure 16-15). A clockwise
rotation causes the selected altitude to in-
crease and a counterclockwise rotation causes
the selected altitude to decrease. Knob selec-
tivity will be 100 feet per detent (30 meters in
metric mode).
16-15
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
