Landing
As the airplane descends and reaches the pre-
selected cabin altitude, the outflow valve mod-
ulates toward the open position. The cabin
should be unpressurized at landing.
SNs 23-003 through 24-139, -170
through -184, -186, -187, and -189, and
25-011 through -026 and -028
On landing, the left squat switch opens the
safety valve which dumps any remaining cabin
pressure upon touchdown .
SNs 24-140 through -169, -185, -188,
-190 through -209, and 25-003 through
-010, -027, and -029 through -045
The left squat switch opens the outflow valve
and dumps any remaining cabin pressure upon
touchdown.
SNs 24-210 through -229 and 25-046
through -063, except -061
Either the left or right squat switch controls the
squat switch relay box. When the airplane lands,
the squat switch relay box opens the outflow
valve and dumps any remaining cabin pressure
into the nose.
EMERGENCY
PRESSURIZATION
Starting with SN 23-030, on those airplanes
modified by SK 23-140 and all subsequent
airplanes, an emergency source of pressur-
ization bleed air is provided to increase the
flow of air into the cabin in the event of a leak
or other malfunction.
On SN 23-030 and subsequent, emergency
pressurization is provided by use of the wind-
shield defog system (see Chapter 10). This is
accomplished by directing bleed air from the
bleed-air manifold through the defog shutoff
valve to the cockpit. By closing the external
defog knob, opening the internal defog knob,
and holding the defog switch to DEFOG for
approximately five seconds, emergency pres-
surization is accomplished.
On model 23 airplanes converted to model 24
and SNs 24-100 and all subsequent airplanes,
bleed air from the bleed-air manifold is routed
through the defog shutoff valve to the cock-
pit by holding either the defog switch to
D E F O G o r t h e W S H L D H E AT s w i t c h t o
AUTO and pushing the IN NORMAL/OUT
DE-FOG knob to IN.
On all airplanes, the AIR BLEED switch is
turned off to isolate any leaks between the
flow control valve and the check valves in the
aft pressurization bulkhead.
12A-12
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international