AMEVoice

Purpose of the OBMS (from A320 Manual) REMEMBER ALWAYS REFER TO THE AMM

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The purpose of the onboard maintenance is to provide maintenance personnel with an aid to fault diagnosis further to a complaint of the crew.

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To accomplish this goal:

(1) Each system includes a Built-In-Test Equipment (BITE) used for detection and isolation of faulty equipment. Furthermore the system is able to initiate tests for the purpose of confirming a fault condition or checking that proper system operation is restored after corrective action.

Remark:

To simplify the task of maintenance personnel:

- the faces of the computers and the maintenance test functions have been standardized

- the maintenance messages are displayed in clear English language and always concern the faulty component or, in some cases, the faulty system.

(2) A Centralized Fault Display Interface Unit (CFDIU) acquires and processes (completes, correlates, memorizes and presents) the data transmitted by the BITEs and the warnings which have originated the crew complaint.

(3) The result of fault diagnosis is displayed to the maintenance operator through the Multipurpose Control and Display Units (MCDU) and the Printer which constitute the user interface.

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Levels of Maintenance

The failure information delivered by the Centralized Fault Display System (CFDS) corresponds to several levels of maintenance.

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(1) Line maintenance

This maintenance is characterized by rapid intervention of maintenance personnel in a short time period; it is limited to the isolation and replacement of a faulty equipment.

This action consists of the identification and/or confirmation of fault condition(s), the isolation of the fault and the replacement of the faulty unit (i.e the Line Replaceable Unit (LRU)).

A test is carried out before and after the removal/installation procedure to check the correct operation of the system.

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(2) Hangar or main base maintenance

This maintenance is characterized by intervention of maintenance personnel in a longer time period and generally concerns actions that cannot be performed at line maintenance level, either because the procedures are too lengthy or because more skilled personnel are required.

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(3) Workshop maintenance

These maintenance actions are performed at regular intervals (check

A, 2A, B...). Intervention of maintenance personnel is then scheduled according to aircraft utilization and concerns the items of equipment for which some mechanical parts are not monitored and/or tested. These failures are called hidden failures.

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B. System BITE Functions

(1) General

- Each electrical or electronic system of the aircraft includes a fault detection, isolating and storing device called a BITE

- A system consists of a set of removable components called LRUs that are specific to the system and that are said to be internal to the system. In many cases, a system uses data from other systems that can be considered as _sensors_ and that are said to be LRUs external to the system.

Example : In an autopilot, the control unit, the computers which determine the laws and the power systems are internal LRUs.

The air data and inertial reference units, the radio altimeter, are external LRUs.

- The BITE system reacts to any fault affecting operation, whether INTERNAL or EXTERNAL to the system.

- Each LRU is a component internal to a given system and no other.

Example : A pressure sensor used for several systems is taken into account as an internal component by one of these systems only.

- All systems including a BITE system are connected to the CFDIU.

- The systems are connected to the CFDIU by means of the system bus.

Exceptions : the FMGS via the FAC 1 and the EFCS via the FCDC use specific b uses.

- The responsibility for fault detection and isolation lies with the system. The CFDS does not perform any processing and it does not modify the diagnosis made by the system.

- For complex systems, one of the computers plays the role of system

BITE, in other words it collects the maintenance data from the peripheral computers and it ensures the interface between the computers and the CFDS.

NOTE : A system BITE is supposed to analyze the data received with a view to establishing a consolidated diagnosis.