(i)
No Flame Shutdown The ECB shuts down the APU if APU light-off (adequate rise in EGT) does not occur within 23 seconds after the fuel shutoff valve is opened.
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CES
(j)
Flap Not Open Shutdown The APU is shutdown if the ECB does not receive the INLET DOOR FULLY OPEN signal within 30 seconds after the APU MASTER SW is set to ON. Additionally the ECB shuts down the APU whenever the APU speed is more than 7 % rpm and the INLET DOOR FULLY OPEN signal is lost for more than 0.5 seconds.
(k)
High Oil Temperature Shutdown The ECB shuts down the APU if the oil temperature is more than 325 deg.F (162.77 deg.C) for 10 seconds.
(l)
No Speed Shutdown The ECB commands an APU shutdown if the APU speed is not more than 7 % rpm within 30 seconds after start sequence was initiated and the air intake flape is open.
(m)
Inlet Overheat Shutdown The ECB commands an APU shutdown if the APU inlet temperature (T2) is more than 350 deg.F (176.66 deg.C) for 3 seconds.
(n)
No Acceleration Shutdown The ECB detects a slow start and shuts down the APU if the start initialization is complete and the
-
Acceleration is less than 0.5 %/s for 60 seconds,
or
-
Acceleration is less than 0.3 %/s for 30 seconds,
or
-
Acceleration is less than 0.1 %/s for 15 seconds and APU is in light-off condition (adequate rise of EGT).
(o)
Reverse Flow Shutdown This shutdown logic is programmed to detect only steady reverse flow (min. 6 seconds). Momentary reverse-flow conditions do not cause an APU shutdown. The reverse-shutdown logic is enabled only when the APU is on-speed. The logic uses the total pressure- (PT) and the differential pressure (DP) transducer signals to sense a reverse-flow.
(p)
Clogged Oil Filter Shutdown The ECB shts down the APU if:
-a clogged oil-filter signal is triggered
and
-
the oil temperature is higher than 100 DEG.F (37.77 DEG.C) and
-
the APU is on governed speed condition (> 95 % rpm).
This shutdown is inhibited during flight (TSO/JAR).
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(q) Main Power Interrupt Shutdown On every APU shutdown (normal or protective), the ECB sets a flag that a regular shutdown sequence has occured. On the next power-up the ECB checks this flag. If it is not set, it indicates that the previous APU run was terminated by a power loss, and the ECB records a loss of DC power shutdown. Power interrupts shorter than 50 msec will not cause a shutdown.
8. BITE Test
_________
The BITE tests the three subsequent BITE modes:
-
The Power Up Test (PUT),
-
The In Operation Test (IOT),
-
The self test if started from the MCDU.
-
GND Scanning For the indication of the report and test pages on the MCDU refer to the chapter 49-73-00 Analyzers.
A.
Power-Up Test (PUT)
The PUT starts if the subsequent signals are available:
-
the power up initialization is complete and
-
the APU speed is below 7 % or
-
the start signal received for more than 60 seconds.
During the PUT the drivers and the loads are tested for open and short.
The switches are tested for their position and the sensor signals are
compared to their limits.
B.
In Operation Test (IOT) The IOT tests all LRUs which are necessary for the APU operation. The IOT starts after the PUT.
C.
Self Test The self test is similar to the power-up test. It is operational when:
-
the test is manual started from the MCDU,
-
the APU speed is less than 7%.
D.
GND Scanning The GND Scanning gives the possibility to show system failure. You get access to the GND Scanning through the MCDU on ground, wether the APU is running or not. When the APU runs and GND Scanning is activated, the failures are shown when they occure. These failures are not memorized.
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