Learjet 20 Series Pilot Training Manual page 333

The slave unit will display the same selected
altitude as the master ("A" illuminated) and ad-
justing its ALT SEL knob will change the se-
lected altitude on both the slave and the master,
as long as the same units (feet or meters) are
selected. If different altitude units of measure
(feet or meters) are selected on the ADDUs,
the preselect display on the slave ADDUs will
blank and its ALT SEL knob will be disabled.
Static Port Switch
The static port switch is capable of isolating
the pilot and copilot air data static sources
(see Figure 16-14). In the normal position
(centered on BOTH), the LH and RH pilot and
copilot static sources are cross coupled and
neither the L or R static port switch annunci-
ators on the air data panel will be illuminated.
To isolate the pilot static air data source, po-
sition the toggle switch to the left, and the L
annunciator illuminates amber. Under this
condition, the pilot ADDU now receives its
static source from the pilot forward static port
while the copilot ADDU receives its static
source from the pilot aft static port. Similarly,
to isolate the copilot static air data source,
position the toggle switch to the right, and
the R annunciator illuminates amber. Under
this condition, the pilot ADDU receives its
static source from the aft copilot static pres-
sure port, while the copilot ADDU receives its
static source from the forward copilot static
pressure port.
NOTE
When the static port switch is used
to isolate the pilot static air data
source, the copilot Mach/airspeed
indicator (MASI) indications should
be considered suspect because the
copilot pitot source could be ques-
tionable. Similarly, when isolating
the copilot static air data source, the
pilot MASI indications should be
considered suspect.
16-16
LEARJET 20 SERIES PILOT TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
Selecting the L or R static port switch could
also affect altitude position corrections as pre-
sented in the "Performance" section of the
AFM Supplement. Therefore, the pilot and
copilot position error correction charts should
not be used when either the L or R static port
switch positions are selected. However, the
standby altimeter position error chart is still
valid.
Standby Altimeter
The standby altimeter is plumbed to the air-
craft static shoulder ports. Power for the al-
t i m e t e r l i g h t i n g i s p r o v i d e d f r o m t h e
emergency battery. The standby altimeter is ca-
pable of displaying altitude in feet and baro-
metric scale in in. Hg or Hpa. Refer to the
"Performance—Altimeter Position Error:
Standby Altimeter" in the Airplane Flight
Manual Supplement to determine correct al-
titude for current flight conditions.
Pitot-Static Probes
Air data sensing is accomplished by utilizing
two heated Rosemount pitot-static probes.
The pilot total pressure is obtained from the
pilot side pitot-static probe. The copilot total
pressure is acquired from the copilot side
probe. The pilot static pressure is acquired by
cross coupling the pilot side forward static
port with the copilot side aft static port.
Similarly, the copilot static pressure is ac-
quired by cross coupling the pilot side aft
static port with the copilot side forward static
port.
Prior to all flights in RVSM airspace, the air-
plane skin surface in the pitot-static probe re-
g i o n ( RV S M c r i t i c a l r e g i o n ) a n d t h e
pitot-static probes must be inspected for ob-
vious damage or deformation. If damage or
surface irregularities are found, the airplane
is not permitted to operate in RVSM airspace.
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