Bleed-Air Control System; Apu Protection System - BOMBARDIER Challenger 601-3A CL-600-2B16 Pilot Training Manual

BLEED-AIR CONTROL SYSTEM

General
The bleed-air control system consists of an
electropneumatic surge valve and an elec-
tropneumatic load control valve.
Surge Valve
The surge valve prevents compressor stalls
and surges during operation when APU bleed
air is not being used. The surge valve is opened
by a signal from the ECU at 10% rpm during
starting and remains open unless the APU
bleed-air switchlight (Figure 6-5) is latched
in when APU rpm is above 95%.
Load Control Valve (LCV)
The LCV is the APU bleed-air valve which
connects the APU air plenum to the airplane's
pneumatic system.
The ECU arms the LCV for operation when
rpm is above 95%. Pushing to latch the APU
bleed-air switchlight (Figure 6-5) will simul-
taneously open the LCV and close the surge
valve. The LCV is monitored by the ECU when
open, and, if operating EGT exceeds design
limits, the ECU will signal the LCV to the
closed position and the surge valve to the open
position. The valves will remain in these posi-
tions until the EGT drops and the ECU allows
the valves to resume their selected positions.
To prevent hot engine bleed-air feedback into
the APU, an electrical interlock circuit will
prevent LCV opening if either or both of the
following conditions exist:
• The left engine 10th stage bleed-air
switchlight is pushed in.
• The right engine 10th stage bleed-air
switchlight and the bleed-air ISOL
switchlight are both pushed in.
An amber FAILED light works through the
electrical interlock circuit. The FAILED light
will illuminate after a five-second time delay
if the load control valve has not closed and one
of the following conditions exists:
6-6 CL 601-3A/R
CL-600-2B16 PILOT TRAINING MANUAL
For more information on APU bleed-air con-
trol, see Chapter 9, "Pneumatics."

APU PROTECTION SYSTEM

The APU protection system provides for
automatic shutdown for any of the follow-
ing conditions:
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
• The left engine 10th stage bleed-air
switchlight is pushed in.
• The right engine 10th stage bleed-air
switchlight and the bleed-air ISOL
switchlight are both pushed in.
• APU overspeed—in excess of design
limit (110%)
• High EGT—in excess of design limit
(732° C) (or an open or shorted ther-
mocouple)
• Overcurrent—excess current demand
by the ECU or any circuit controlled by
the ECU
• APU low oil pressure—APU oil pressure
below the minimum design limit when
APU rpm is above 95%
• APU high oil temperature—APU oil
temperature in excess of design limit
for 1 second
• Generator adapter low oil pressure—
generator adapter oil pressure below
minimum design limit for 10 seconds
• Generator adapter high oil tempera-
ture—generator adapter oil temperature
above design limit
• APU OVERHEAT or fire—Overheat or
fire detected by the APU fire sensing
loop
NOTE
Pushing the APU FIRE PUSH switch
will also cause an APU shutdown.
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