(2)
APU in Operation When the APU operates outside of its set limits, the ECB shuts it down automatically. The ECB does this in relation to the APU configuration and flight phase. The fault is kept in the BITE fault memory. An overspeed or an emergency stop signal will also cause the APU to shut down. This is not related to the configuration.
C. Self Test The BITE of the ECB does a self test of the APU systems with the APU off line (not in operation) through an ARINC 429 bus. The BITE examines all the internal ECB and external APU circuits. A record of LRU failures is transmitted to the CFDS. A self test is also used to make sure that the system is satisfactory after maintenance action has been taken. The self test cannot occur when the APU speed is more than 7 %. The self test takes approximately 3 s.
D. Table of LRUs examined through the BITE of the ECB in different test modes.
Table 1
------------------------------------------------------------------------------NO | LRU | TEST MODE | ALTERNATE | | PUT | IOT | SELF TEST | VALUE
-------+--------------------------+-------+-------+-------------+-------------1 | MAIN START CONTACTOR | X | X | X | 2 | BACK UP START CONTACTOR | X | X | X | 3 | STARTER MOTOR | | X | | 4 | HOT SWITCH | X | | X | 5 | LOW OIL LEVEL SWITCHES | X | | X | 6 | LOP SWITCH | X | | X | 7 | LCIT SENSOR | X | X | X | X 8 | LCDT SENSOR | X | X | X | X 9 | GENERATOR OIL TEMP SENSOR| X | X | X | X
10 | SPEED SENSORS | X* | X | X* |
11 | DELTA P SENSOR | X | X | X | X
12 | PT SENSOR | X | X | X | X
13 | P2 SENSOR | X | X | X | X
14 | APU SERIAL NO. ENCODER | X | X | X |
15 | EGT SENSORS | X | X | X |
16 | APU OIL TEMP SENSOR | X | X | X | X
17 | LOAD VALVE POS. SWITCHES | X | | X |
18 | ECS DEMAND | | X | |
19 | AIR INTAKE FLAP ACTUATOR | X | | X |
20 | DE-OIL SOLENOID | X | | X |
21 | FUEL SOLENOID | X | X | X |
------------------------------------------------------------------------------
NO | LRU | TEST MODE | ALTERNATE | | PUT | IOT | SELF TEST | VALUE
-------+--------------------------+-------+-------+-------------+-------------22 | LOAD VALVE | X | X | X | 23 | IGNITION UNIT | X | | X | 24 | FUEL TORQUE MOTOR | X | X | X | 25 | SURGE VALVE TORQUE MOTOR | X | | X | 26 | IGV ACTUATOR | X | | X | 27 | ECB | X | X | X | 28 | GEN/SCAV OIL FILTER | X | | X |
NOTE : X* = The input signal conditioners are tested for possible
____ failures in some modes since input signals are known within reasonable limits.
R **ON A/C 063-099, 401-499,
The BITE of the ECB 59KD operates in three main modes:
-Power Up Test (PUT) mode,
-In Operation Test (IOT) mode,
-self test mode. The test mode in which the ECB operates is related to the step of APU operation and also which of the LRUs are examined. A list of the LRUs examined by the ECB BITE during the different test modes is shown in Table 1.
A. Power Up Test (PUT) The BITE of the ECB 59KD automatically starts the PUT when the MASTER SW 14KD is set to ON. The BITE sends test signals to the different control system components and sensors, and makes an analysis of the replies. The ECB then makes a logic decision (with the use of the data collected) to permit or stop an APU start attempt. The ECB can also permit the APU start to continue, although some unimportant LRUs have failed; it uses alternative control values and schedules. The LRU failures are kept in the BITE fault memory for 64 legs. The ECB prevents an APU start until the PUT is completed. This will take approximately 3 s.
B. In Operation Test (IOT) The IOT mode functions during the APU start up, operation and shutdown. The BITE of the ECB 59KD continuously monitors the APU operation limits. It makes sure that the APU operates in a pre-programmed envelope. The LRU failures are kept in the BITE fault memory. The ECB, with the ECB configuration known, and the record of LRU failures can:
-start an automatic shutdown, or,
-
continue operation with the use of alternative values for the failed LRUs, or,
-
continue operation if LRUs fail.
(1)
APU Start During an APU start, the BITE of the ECB monitors the APU performance and will stop the sequence if the APU goes out of limits (a pre-programmed envelope). The cause is kept in the BITE fault memory.
(2)
APU in Operation When the APU operates outside of its set limits, the ECB shuts it down automatically. The ECB does this in relation to the APU configuration and flight phase. The fault is kept in the BITE fault memory. An overspeed or an emergency stop signal will also cause the APU to shut down. This is not related to the configuration.
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