(b)
The BITE self-test mode is initiated by pressing the TEST button on the EICAS Maintenance Panel. A second press of the TEST button or release of the parking brake will cause the computers to exit the test mode.
(c)
The BITE self-test mode is also initiated by a program pin error.
(d)
A self-test routine involves an end-to-end test of system health. When the TEST button is pressed, internally generated signals drive the input receivers of each computer. Each EICAS computer responds independently to the test. All the automatic monitoring described above continues except for crosstalk input data comparison. Any disagreement detected previously during system operation is retained in memory for display on the test page.
(e)
The system conducts a single self-test cycle and responds in the following manner. 1) The master caution light output discrete is set to ground.
This causes the two master CAUTION lights to come on.
2) The aural command output discrete is set to ground. This signal causes the WEU to sound the caution owl aural (Ref 31-51-00).
3) The take-off thrust output discrete is set to ground. This signal enables the WEU to output its takeoff-configuration warning siren signals (Ref 31-51-00).
4) The test page displays TEST IN PROGRESS during test signal processing. After processing is finished, the ground is removed from the output discretes. The warning siren from the WEU will cease, but the master CAUTION lights will remain on until they are manually reset.
ú
31-41-00
ALL ú ú 23 Page 53 ú May 28/01
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757
MAINTENANCE MANUAL
(f) The results of the test are displayed as follows: 1) The message SELF TEST COMPLETE appears in the top left. 2) The two classes of faults, INTERFACE FAULTS and INTERNAL
FAULTS, appear below the SELF TEST COMPLETE message. a) If faults are found, the quantity of faults appear to the left of fault type. b) If there are no faults, the word NO appears instead of the quantity. 3) The faults are stored in fault reporting pages; PRESENT STATUS and FAULT HISTORY. 4) VIEW PRESENT STATUS and CLEAR TEST RESULTS show if there were any faults recorded during the current flight leg. 5) The faults for the current flight leg are found in the PRESENT STATUS fault reporting page(s). 6) From the EICAS self test page, you push the MAN switch twice to show the PRESENT STATUS summary page.
NOTE: The PRESENT STATUS page will only show if there
____ are faults. The display will not change if there are no faults.
7) The title LEFT(RIGHT) EICAS COMPUTER, along with PRESENT STATUS, appears at the top center of the summary page.
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