Protection Systems; Normal Differential Control; Overpressure Limiter; Altitude Limiter - BOMBARDIER Challenger 601-3A CL-600-2B16 Pilot Training Manual

PROTECTION SYSTEMS

The protection systems incorporated in the
pressurization system are:

• Normal differential control

• Overpressure limiter (maximum differ-
ential)

• Altitude limiter

• Negative pressure relief

NORMAL DIFFERENTIAL
CONTROL
The normal differential control is an auto-
matic function of the pressurization controller
when operating in the AUTO mode. Normal
differential pressure for the controller is lim-
ited to 8.8 psid.

OVERPRESSURE LIMITER

Each outflow valve includes an overpressure
limiter that constantly senses the difference be-
tween cabin pressure and atmospheric pressure.
If this value reaches approximately 9.1 psid, ei-
ther, or both, valve(s) will respond and increase
the metering rate to limit the differential.
ALTITUDE LIMITER
Each outflow valve includes an altitude lim-
iter to prevent cabin altitude from exceeding
a preset value. Cabin pressure is admitted to
a sealed bellows chamber, compressing the
bellows and keeping a valve closed. If cabin
altitude reaches approximately 13,000 ±500
feet, the bellows will expand (because of the
decreasing cabin pressure) and open the limit
valve. The outflow valve will close and limit
the cabin altitude to approximately 13,000
±500 feet.
CL-600-2B16 PILOT TRAINING MANUAL
NEGATIVE PRESSURE RELIEF
A negative pressure-relief feature is part of
each outflow valve to prevent atmospheric
pressure from exceeding cabin pressure. In
effect, one side of each outflow valve di-
aphragm is exposed to atmospheric pressure
while the opposite side is exposed to cabin
pressure. If the atmosphere to cabin pressure
differential reaches approximately 0.5 psid,
atmospheric pressure will open the outflow
valve poppets and equalize the cabin and at-
mospheric pressures. If this occurs during de-
scent, the cabin will descend at the same rate
as the airplane. This can produce physical dis-
comfort if the rate is sufficiently high.

PNEUMATIC RELAY

A pneumatic relay is incorporated in the pneu-
matic (right) outflow valve only. In the auto-
matic mode, the pneumatic relay is inactive.
Loss of battery bus power or moving the
MODE switch to MANual activates the pneu-
m a t i c r e l a y w h i c h t h e n r e s p o n d s t o t h e
MANual regulator UP-DOWN lever and the
manual RATE knob to control the metering rate
of both outflow valves.
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL 601-3R 12-5
L t é e
L t d .