ENGINE 1
THRUST REVERSER AUTO RESTOW

NOTE:  ENGINES 2,3,&4 SAME AS ENGINE 1. SUPPLIES DISCRETE OUTPUT DRIVER

PSEU Logic Diagram Figure 3 (Sheet 10)
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 (b)  The discrete output signals are as follows:
 -Nose Gear Not Down and Locked - Used by Instrument Landing System (ILS)
 -Landing Gear Lever Unlock - Used to energize the landing gear lever unlock solenoid
 -Autospoiler Enable - Used to energize the autospoiler relays
 -Air Mode - Used to energize air/ground relays
 -Ground Mode - Used to energize air/ground relays
 -
Nose Gear Compressed - Used to energize nose gear steering relays

 -
Nose Gear Not Compressed - Used to energize nose gear steering relays

 -All Gear Down - Used by Stabilizer Trim/Rudder Ratio Module (SRM).
 (3)  
The PSEU has BITE (Built-In-Test-Equipment) to find failures and help trouble shoot the PSEU. BITE continuously monitors PSEU inputs, internal components, printed circuit cards, and operations important to correct PSEU operation. It makes sure that the circuits operate correctly. BITE compares the hardware operation of circuits to the software operation in the PSEU.

 (a)  
If a failure is found, the PSEU BITE operation will isolate the failure to the line replaceable unit (LRU).

 (b)  
After replacement of the LRU, BITE can make sure the hardware interfaces work correctly.

 (c)  
The LRUs for the PSEU system are the proximity sensors and the PSEU.

 (d)  
When a sensor or sensor wiring fails, BITE finds the defective sensor.

 (e)  
There are two types of failure, line relevant failures and shop relevant failures. 1) Line relevant failures are failures which need work by line

 technicians. Line relevant failures are as follows:
 -Sensors and related wiring
 -Discrete inputs
 -ARINC 429 receiver
 -Failed PSEU.
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 2)  Shop relevant failures are failures which need necessary work by shop technicians. These failures would cause replacement or repair of printed circuit boards, wiring, or assemblies. Shop relevant failures are as follows:
 -
Failed ARINC 429 receiver

 -
Failed ARINC 429 transmitter

 -
Failed printed circuit cards

 -ARINC 429 data ports disagree
 -Circuit cards that you cannot use together in the same PSEU.
 (f)  Failure Isolation 1) All line relevant failures are isolated as follows:
 -
Sensor failed

 -
Sensor or associated wiring open

 -
Sensor or associated wiring short

 -Discrete inputs are not in a correct state
 -ARINC 429 receiver port:
 -No data received for 3 seconds
 -Failure warning bit set
 -Parity error
 -Digital word has more than 32 bits
 -
One of the two ends of the transmission line is open

 -
One of the two ends of the transmission line is shorted to ground

 -
One of the two ends of the transmission line is voltage falling

 -Failed PSEU
 -Target position error
 -
Subsystem failed 2) Shop relevant failures are found in the levels as follows:

 -
Subsystem

 -Printed circuit board - proximity channel, logic path, or driver channel.
 (g) Failure Storage 1) The CMC keeps a record of line relevant failures. Use the CMC to find if the failure is continuous or not continuous. The PSEU does not keep a record of line relevant failures.
 2)  The PSEU non-volatile memory keeps a record of shop relevant failures. The memory also keeps a record of the flight leg number and the type of failure.
　
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