Learjet 20 Series Pilot Training Manual page 345

pilot's sidewall (Figure 17-8), and the third is
solenoid-operated by an aneroid switch. The
manually controlled PASS OXY (forward) valve
is normally in the NORM (open) position, which
allows oxygen up to the manually controlled
PASS MASK (aft) valve and to the aneroid-
controlled solenoid valve. Oxygen can be
admitted to the passenger distribution system
through either of these passenger mask valves,
both of which are normally in the closed position.
With the PASS OXY valve in the OFF (closed)
position, oxygen will not be available to the
passenger distribution system in any event. This
position may be used only when no passengers
are being carried.
With the PASS OXY valve in the NORM (open)
position, oxygen will be automatically admitted to
the passenger distribution system through the
aneroid-controlled solenoid valve if the cabin
reaches 14,000 ±750 feet. The aneroid switch
opens the solenoid valve and deploys the passenger
masks. On SNs 24-256 and subsequent and 25-095
and subsequent, it also illuminates the cabin
overhead lights.
In the event of aircraft electrical failure, automatic
deployment of the passenger masks is not possible.
The oxygen solenoid valve requires DC power
through the OXY VAL circuit breaker for
automatic mask deployment.
PASS MASK VALVE
17-8
LEARJET 20 SERIES PILOT TRAINING MANUAL
Figure 17-8. Passenger Oxygen System Controls
FOR TRAINING PURPOSES ONLY
With the PASS OXY valve in the NORM (open)
position, rotating the PASS MASK valve from
AUTO to the MAN position admits oxygen into the
passenger distribution system and causes the
passenger oxygen masks to drop. This position can
be used to deploy the passenger masks at any
altitude, but will not cause the cabin overhead lights
to illuminate.
Figure 17-9. Passenger Mask
FlightSafety
international
ELASTIC STRAP
OXYGEN MASK
REBREATHER BAG
PASS OXY VALVE