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installed on airplanes SN 1156-1252 equipped with SPZ-8000
DAFCS. The upper half contains the red text annunciation of APU
LOAD that is illuminated if electrical loads exceed limits and must be
reduced when operating above 30,000 feet. The lower half contains
the amber text annunciation of APU LOAD that illuminates when
APU electrical loads are nearing limits when at high altitudes.
• ELWS FAIL (amber) / ELWS CONFIG (amber) - is a split
annunciator installed on airplanes SN 1034, and 1156-1429. The
upper half contains the amber text annunciation of ELWS FAIL that
is illuminated when the system is unreliable for monitoring APU
electrical loads. The lower half contains the amber text ELWS
CONFIG that illuminates when the Electrical Power Monitoring
Panel (EPMP) is not properly conÞgured for ELWS operation.
2. Tail Compartment Controls and Indications:
A. APU Remote Failure Indicator Box:
A remote failure indicator box for the APU is mounted in the tail
compartment to facilitate maintenance on the APU. The box has magnetic
ÒcatÕs eyeÓ indicators that are activated whenever a malfunction causes an
automatic shutdown of the APU. The box has indicators for:
• H-OIL TEMP - high oil temperature auto-shutdown
• L-OIL PRESS - low oil pressure auto-shutdown
• OV CUR - auto-shutdown caused by an overcurrent in the APU ECU
circuitry (not the alternator)
• OV TEMP - high EGT auto-shutdown
The indicator box also has two toggle switches. One toggle switch resets
the failure indicators, the other toggle switch shuts down the APU using the
same overspeed signal as the OVSP TEST-STOP switch on the cockpit
APU control panel.
B. Hourmeter:
An hourmeter is installed in the tail compartment near the APU enclosure
(location varies) to log the operating time of the APU. The meter is
activated when the APU RPM reaches 95% and displays the cumulative
time of APU operation. The meter is used to determine when to perform
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-49-00
Page 11
October 11/02
Revision 8
required maintenance checks that are speciÞed after a certain number of
APU operating hours.
3. APU Start Sequence:
During an APU start, the following indications are normally observed (it is
assumed that normal preßight and prestart procedures outlined in section
03-02-00 of this manual have been accomplished):
• APU MASTER switch ON - air inlet door opens, fuel shutoff valve in left
wing tank opens, and, when air inlet fully open, OIL PRESS LOW indicator
illuminated
• START switch depressed and held until RPM rise indicated, switch is then
held in electrically
• At 10% RPM, APU fuel valve opens and ignition is powered, EGT rises
• At 25% RPM, an acceleration timer started by ECU. Timer monitors start
for 16 seconds or until RPM reaches 95% for 4 seconds
• At 30% RPM, OIL PRESS LOW light should extinguish and oil pressure
should indicate approximately 40 psi
• Acceleration up to 60%, EGT should not exceed 988¡C
• At 60% RPM, the START switch disengages, indicated by the ON legend in
switch extinguishing, surge valve opens, EGT begins decreasing
• At 95% RPM, after a 4 second ECU initiated delay, ignition is terminated,
the bleed air load control valve and alternator are available, and the
hourmeter begins tracking APU operating hours
• At 100% (±3%), EGT should stabilize at approximately 665¡C. After RPM
has stabilized for 1 to 2 minutes, electrical and pneumatic loads may be
placed on the APU.
4. CAS Messages:
A. Warning (Red) CAS Messages:
CAS Message Cause or Meaning
APU FIRE APU Þre detected
APU LOAD (1) APU electrical load not within limits for operation above
30,000 feet
NOTE(S):
(1) SN 1034, 1156-1252 with SPZ-8400 and 1253-1429
B. Caution (Amber) CAS Messages:
CAS Message Cause or Meaning
APU ALT BRG FAIL Main bearing of APU alternator has failed and alternator is
operating using the auxiliary bearing
APU ALT HOT APU alternator above 300¡F /149¡C
APU LOAD (1) APU electrical load not within limits for operation above
30,000 feet
APU MASTER WARN APU MASTER switch in the ON position but APU is not
running
AUX AC POWER FAIL APU alternator has failed or dropped off line
OPERATING MANUAL
2A-49-00 PRODUCTION AIRCRAFT SYSTEMS
Page 12
October 11/02
Revision 8
NOTE(S):
(1) SN 1034, 1156-1252 with SPZ-8400 and 1253-1429
C. Advisory (Blue) CAS Messages:
CAS Message Cause or Meaning
APU ALT OFF AUX PWR switch on Electric Master panel not selected
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