b LGCIU 1 in control of the L/G, LGCIU 1 Fails.
_ LGCIU 1 sets its status to 'On Standby'. LGCIU 2 observes that LGCIU 1 is 'On Standby' so it becomes 'Active' and takes and maintains control of the L/G system.
c Both LGCIU's Failed.
_ If both of the LGCIU's should fail, then both of the LGCIU's will set their status to 'On Standby'. Thus neither of the LGCIU's will have control of the L/G system.
Failure Monitoring
The software continuously monitors the performance of the LGCIU/system hardware. The main functions monitored are:
-proximity sensor outputs
-
L/G control-logic outputs
-
L/G control-lever inputs (UP and DOWN)
-electrical power supplies
-discrete (transistor) outputs
-ARINC 429 transceiver inputs and outputs exited in the correct sequence.
-memory failure (EPROM, RAM, NOVOL).
To detect failures in the hardware the software uses a comparison technique for example:
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4
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5
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it compares the two output signals from each proximity sensor
-
it compares each discrete output signal with the proximity-sensor input-signal.
When a failure is detected that does not affect the control of the L/G system, the LGCIU continues to be/become the 'Active' unit. The details of a failure are stored in the NOVOL memory and reported to the CFDS.
The software is monitored for failure by itself and a Watchdog Timer. The software monitors itself by the use of an audit trail technique. This is a software procedure that makes sure that each software process is entered and exited in the correct sequence. The Watchdog Timer's function is to check the software for serviceability at regular intervals. A serviceable software causes the Watchdog Timer to be reset. Should the software fail, the Watchdog timer will not be reset and this causes the LGCIU to change its status to 'On Standby'.
System Status/Maintenance Data Transmissions
The software continuously monitors the performance of the LGCIU and the inputs from the proximity sensors. The data collected is processed by the microprocessor and transmitted on the ARINC 429 data buses to:
-
the CFDS
-
the FWC (for ECAM display)
-
the SFCC's
-
the Cargo Door system
- other systems connected by ARINC 429 data buses (Ref. 32-62-00).
This is the function which also forms the ARINC 429 words that contain the system status and maintenance data.
Fault Logging
This software function stores failure and maintenance data in the NOVOL memory for later transmission to the CFDS. Failure data can be transmitted to the CFDS up to 64 flights after the failure occurred.
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6_ BITE
The software provides a Built in Test Equipment (BITE)
function which is additional to the continuous failure
monitoring function. The BITE test is started by manual use of
the CFDIU (Menu Mode) and takes approximately 7 seconds to
complete (Ref. 32-69-00).
The BITE test is inhibited:
- at aircraft wheel speeds greater than 70kts
- during flight.
7_ Landing Gear (L/G) Configuration Simulation
The L/G Configuration Simulation function is able to simulate
any or all of the landing gear configurations. This function
is provided for the use of the maintenance crew during test
and failure investigation tasks. It is inhibited during
flight.
A L/G Configuration Simulation is selected by manual use of a
CFDIU (Menu Mode (Ref. 31-32-00). While the LGCIU is in a L/G
simulation mode it will continue to supply both ARINC 429 and
discrete output signals.
8_ Intel 8251 RS232C Interface Device
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