(10)
 <CLASS 3 FAULTS> This gives every class 3 fault that has occurred, see Table 4. The MCDU display format changes. The change is related to the mode selection that is made. The text of the LRU failures is related to which LRU has failed. A sample of the LRU failures is given in Table

 4. A flight 'LEG' is specified as from initial power up, through flight, to power off after the aircraft has landed.

 H.
 LRU Faults, Shutdowns and Fault Tree Three classes of LRU faults exist, class 1 are the most serious and class 3 are the least serious. When certain class 1 LRU faults are detected, the ECB initiates an APU shutdown (if not inhibited) due to the impact of the failed LRU on the overall system operation. The class of the LRU faults and the text, sent to the CFDS, are shown in table 2, 3 and 4. The protective shutdowns with their associated text, shown on the APU shutdown page of the CFDS, are presented in table 5.

 The fault tree (table 5, col. 4) is used to associate a protective shutdown with a failed LRU that caused the shutdown. The fault tree is used in the following manner: If a protective shutdown occurs, the ECB search the fault tree for this particular shutdown. Once the shutdown is located, the ECB shall compare any failed LRUs that where detected on the current APU run with the LRU faults associated with the shutdown reason. If a failed LRU matches one of the LRUs associated with the shutdown reason, the failed LRU is displayed together with the shutdown reason on the APU shutdown page of the CFDS. If no current failed LRU matches an LRU associated with a particular shutdown reason, the ECB displays the shutdown reason and a list of LRUs which most probably caused the APU to shutdown (table 5, col. 3).
 J. BITE Detection
 (1) CLASS 1 Faults
 Table 2
 NOTE : FCN is an internal ECB-software Failure Code Number. Refer.
____
 also table 5

 -------------------------------------------------------------------------------
Text for CFDS Indication | ATA | BITE Detection (Failed LRUs) | FCN ============================+==========+================================+======
 AIR INTAKE FLAP ACTR  | 49-16-51 | Air Inlet door NOT open | 00 | | Inlet door open circuit FAIL. | | | Open circuit FAILURE | | | Inlete door open switch FAILURE|
 ----------------------------+----------+--------------------------------+------IGNITION UNIT P10 | 49-41-38 | Ignition Unit | 02 ----------------------------+----------+--------------------------------+------LOAD CTL VALVE P12 | 49-51-51 | Load Valve Solenoid | 03 ----------------------------+----------+--------------------------------+------DEOILING SOL P15 | 49-91-49 | Deoiling solenoid | 04
 ----------------------------+----------+--------------------------------+------FUEL CTL UNIT | 49-32-11 | Fuel solenoid or | 05 | | Fuel torque motor | ----------------------------+----------+--------------------------------+------- - -| - - -| No APU connected | 08
 ----------------------------+----------+--------------------------------+------DIFFERENTIAL PRESS XDRC | 49-51-16 | DP transducer | 13 P24 | | |
 ----------------------------+----------+--------------------------------+------OIL PRESS SW P14 | 49-94-14 | Low oil pressure switch | 14 ----------------------------+----------+--------------------------------+------OIL SUMP TEMP SNSR P25 | 49-91-51 | Oil sump temperature sensor | 16
 ----------------------------+----------+--------------------------------+------INLET GUIDE VANE ACTR | 49-23-51 | IGV actuator torque motor | 20 P21 | | |
 ----------------------------+----------+--------------------------------+------SURGE CTL VALVE P18 | 49-51-52 | Surge valve torque motor | 21 ----------------------------+----------+--------------------------------+------
ECB 59KD  | 49-61-34 | ECB internal failure: | 27 | | drv. for import. LRUs fault or | | | memory fault or | | | speed converter fault or | | | AD converter fault |
 ----------------------------+----------+--------------------------------+------CONTACTOR 5KA | 49-42-41 | Main start contactor failed, | 28 | | open or short | ----------------------------+----------+--------------------------------+------CONTACTOR 10KA | 49-42-42 | Back-up start contactor failed,| 29 | | open or short | ----------------------------+----------+--------------------------------+------SPEED SNSRS P26,P27 | 49-71-13 | Speed sensors 1 and 2 | 39
 ----------------------------+----------+--------------------------------+------SPEED SNSR P26 AND ECB | 49-71-13 | Speed sensor 1 and opposite | 40 59KD | | speed converter |

 -------------------------------------------------------------------------------
Text for CFDS Indication | ATA | BITE Detection (Failed LRUs) | FCN ============================+==========+================================+====== ----------------------------+----------+--------------------------------+------
　
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