Cabin Blower Distribution
The cabin bower assembly consists of a squirrel-
cage blower(s) driven by a DC motor. The
blowers draw air from the cabin through the
evaporator and discharge through adjustable
louvered vents behind the pilot on SNs 23-003
through 24-129, and through the single or dual
ducts located on the ceiling above the baggage
compartment in later airplanes. When installed,
the optional heating elements are located
within these ducts.
On airplanes with dual ducts, two variable-
position diverter doors are installed, one on the
bottom of each duct. They are manually con-
trolled by the CLOSE–OPEN knob adjacent to
the louvered grille (Figure 11-15). When rotated
in the OPEN direction, both diverter doors are
raised up into the path of the blower airflow,
causing some of the flow to be diverted back into
the baggage area. This results in a reduction of
the airflow into the cabin. When the knob is
rotated to its extreme in the CLOSE direction,
the doors are flushed with the bottom of the
ducting, maximizing airflow into the cabin.
Cockpit Fan Distribution
Between the two ducts fed by the cabin blowers
is another duct which encloses the axial cock-
pit fan. The cockpit fan is a 28-VDC fan con-
trolled by a rheostat located on the copilot’s
sidewall (Figure 11-16). This fan draws air from
the baggage compartment area. These ducts run
directly to the overhead outlets in the cockpit.
The cabin blower is controlled by the FAN
position on the COOL SYS–OFF–FAN switch
on the climate control panel (Figure 11-17). The
cockpit cooling fan is controlled by a rheostat
on the copilot’s side panel.
Figure 11-16.
Fan Rheostat
Figure 11-17.
COOL SYS–OFF–FAN Switch
AUXILIARY COOL SYSTEM
The Freon refrigeration system is installed to
provide supplemental cooling for ground and
in-flight operations and can also be used for
dehumidification. See Figure 11-18 for the
system diagram.
11-14
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
Figure 11-15.
Diverter Door Control
