electronic flight instrument system.doc

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Electronic Flight Instrument System

Airbus A340

Introduction

The Electronic Flight Instrument System (EFIS) is an avionics system

connected with most of the aircraft systems to carry out the two following

main display functions, EFIS Display Function and ECAM Display Function:

(1) EFIS display function

The EFIS display function is shared in two, one for CAPTAIN and one for

FIRST OFFICER.

Each crew member has at his disposal two displays presenting the whole

FLIGHT information (for safe flight and navigation), the PFD and the ND.

(a) The two Primary Flight Displays present the following short term data:

- Attitude angles:

i- Pitch

ii- Roll

iii- Heading

- Airspeed indications: computed Airspeed and various manoeuvring or

limit speeds,

- Altitude, vertical speed,

- Trajectory deviations (ILS),

- Automatic flight mode announcement,

- TCAS alert.

(b) The two Navigational Displays present the following long term data:

- Radio navigation (VOR, DME, ILS, MLS, ADF),

- Flight management paths

- Weather radar mapping

- TCAS report.


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(2) ECAM display function

The ECAM display function is unique for both crew members

(For further details, Ref. to 31-50-00).The ECAM display function presents the whole aircraft information via two

displays : the EWD and the SD.

(a) The EWD presents the following data:

- Engines primary indications,

- Slats/flaps positions,

- Warning/memo messages related to the main systems of the aircraft.

(For further details, Ref. to 31-66-00).

The Electronic Flight Instrument System (EFIS) architecture is designed to

cope with requirements in regard to:-

- REDUNDANCY

(2 Primary Flight Displays, 2 Navigational Displays, 1 Engine Warning

Display, 1 System Display, 3 DMCs),

- SEGREGATION

(4 types of symbologies (PFD, ND, EWD, SD), Primary Flight Display,

Navigational Display, Engine Warning Display and System Display),

- RECONFIGURATION capabilities for minimization of operational

consequences and maximization of A/C availability in case of any

Electronic Instrument System component failure.


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This reconfiguration function is mainly aimed at changing the six displays

of the main instrument panel whenever necessary.

These displays are:

- The Primary Flight Display (PFD) : all information related to the

behaviour of the aircraft

with respect to pitch and roll axes.

- The Navigation Display (ND): all information related to the behaviour of

the aircraft with respect to yaw axis

describing the aircraft horizontal situation.


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- The Engine/Warning Display (EWD):

ENGINE area : engine parameters fuel on board

slat and flap position indication.

WARNING area : All equipment failures together with their

consequences on the flight.

- The System/Status Display (SD) : a sketch of the main aircraft systems

with a symbology relating the behavior of

most of the items of equipment concerned

by the system.

-Weight saving objectives have led to the design of the EFIS which enables

to draw all these displays on six display units (DUs).

-Three Display Management Computers (DMCs) drive the displays.

-The EFIS reconfiguration function is achieved by means of a set of

switching devices plus some software implements within the DMC and the

DU to enable reconfiguration of these system parts which include a failed

component.-Various reconfiguration (more on page 9.) possibilities are provided in

the EFIS in order to cope with the operational requirements in case of

failure of:

- a bus input

- a DMC

- a DU

- a control panel (EFIS control panel of the Flight Control Unit (FCU) or

ECAM control panel).

More Explanation on the

reconfigurat

ion in page

9.


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Component Description

(1) General

The EFIS display functions are performed by the 3 DMCs and the 6 DUs.

The DMCs receive data from different avionics systems in the aircraft,

decode them and process them in such a way so that the externally

connected DUs in the cockpit can use them to generate symbols and

pictures on their screens.

(1.1) DMC description


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The 3 DMCs are identical and interchangeable.

The DMCs are able to perform the EFIS function or the ECAM function.

Each DMC is independent from the other and has its own:

a) power supply module

b) acquisition modules

c) processing channel.

(a) Power supply


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The DMCs are supplied from various buses (115VAC from NORMAL and

EMERGENCY A/C network) to ensure that at least two DMCs remain

available in case of emergency configuration. The DMCs also receive

28VDC for WXR, and output discrete.

(b) Acquisition modules

The acquisition modules enable the DMCs to handle all the input signals

from the other avionics systems, and to convert them in a suitable format

before memorization.

If one acquisition module fails, the operation of the other one is not

affected.

(c) Processing channel

1 - Validation/selection

Before processing, the validity of data is checked: if it is not satisfactory,

another source is selected.

2 - Emission

- Data processing: the data memorized in the acquisition module are

processed by the CPU then stored for transmission via the A629 link,

together with some orders to generate the

right image onto the DUs.

- Parameters are sent to the DMC peripherals on an ARINC 429 output

bus.

This output bus goes through an aircraft wiring switching stage which

enables continuous supply after system reconfiguration.

(d) Other functions

1 - Switching

A WXR switching function selects the WXR tranceiver in contol on the

CAPT/ FO side and coming from the DMC1, 2 or 3.


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DU Monitoring

Each DU monitors two of the remaining five DUs by comparing the critical

parameters value at the DMC relevant input and the value of the same

parameters returning on the ARINC 629 feedback bus.-When a discrepancy is detected, a message related to the faulty DU is

displayed on the monitoring DU and a warning is sent to the FWC.

3 - Test function

The BITE test is performed in the DMC and the results are stored for later

transfer to the Central Maintenance System (CMS).

(1.2) DU description

The 6 DUs are identical and interchangeable. Each DU receives digital

signals from its related DMC through an A629 Link, and also through a

particular bus (A453) for the weather radar link. These digital signals

convey instructions and data corresponding to the displays to be

presented on the DUs.

DMC Technical Data

(1) Housing

- Size : 6 MCU

- Colour : brown.


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- Number of boards : on the face, 5 boards on the back, 1 mother

boards

and protection boards.

- Number of connectors : 1 ARINC 600, size 3.- Total weight : 5.5 kg.

(a) Input capacity

- discrete : 108 (type: open/ground or 28VDC/open)

- ARINC 429 : 99 channels (low speed or high speed)

- ARINC 629 : 8 channels (high speed)

- ARINC 453 : 4 channels

(b) Output capacity

- Discrete : 13 (type: open/ground or 28VDC/open)


- ARINC 629 : 2 channels

- ARINC 453 : 1 channel

- RS232 : 2 channels for flight test only

- ETHERNET : 2 channels for data loading

(c) Cooling

Standard ARINC 600 cooling.

(2) DU Technical Data

(a) Size of the screen

The available size of the screen is a flat square of 6.25 X 6.25 inches,

slightly larger than the former CRT technology.


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(b) Weight : 7.6 kg

(c) Input capacity- Discrete : 18 (type: open/ground or 28VDC/open)


- ARINC 629 : 3 channels used, 2 full provision channels and

wrap around

- ARINC 453 : 1 channel

- Discrete : 1 (type: 28VDC/open)

- Analog DC : 3 plus 2 reference voltages and one cell provision

A set ofswitching devices and some automatic processes are

provided to the crew. They are:

- Two EFIS DMC selector switches, one on the Captain side, the other on

the

First Officer side.

- Two PFD/ND pushbutton switches, one on the Captain side, the other on

the

First Officer side.

- One ECAM SWITCHING/DMC selector switch

- One ECAM SWITCHING/ECAM/ND selector switch for ECAM/CAPT ND or

ECAM/F/O ND

transfer.

- automatic DU switching available after a PFD DU fault or an EWD DU

fault.


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Reconfiguration.

A. Power Supply Reconfiguration

The power supply system also enables some reconfigurations when some

supply sources are missing.

B. Source Reconfiguration

Some sources are reconfigured manually (flight management - air data -

inertial reference ), some others are reconfigured automatically (flight

guidance - radio altimeter).

Some input sources are fully redundant (engine sources), whereas some

others loss their data when they fail (central maintenance computer).

These reconfigurations are described in A340 Maintenance Manualpage

31-62-00 (EFIS data acquisition).

C. Reconfiguration in Case of an EFIS Component Failure

In order to achieve satisfactory redundancy of the system the following

principles have been adopted:

D. EFIS Reconfiguration Devices

The reconfiguration function includes:

- a set of pushbutton switches, selector switches and potentiometers to

enable the crew manual action

- a set of external relays (separate from the DMC and the DU)

- some software processes implemented in the general application

software program teleloaded from the F.L.A.S.H.

These devices allow to cope with:

- a single DMC failure

- a dual DMC failure

- a single DU failure

- a dual DU failure

Furthermore a combination of some of these failures has been taken into

account.


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(1) A reconfiguration takes place only when:

- The DMC which drives a display unit is faulty

- A DU is faulty (or switched off).

In all cases manual switching has priority over automatic switching.

(2) DMC source reconfiguration

-When one EFIS normal source is faulty, the crew select the DMC3 source

first.

-Then, when the DMC3 fails in turn, the crew select the remaining

opposite DMC. This operation is the COPY mode.

-Whatever the actual configuration, the DMC which drives the CAPT PFD

and ND is the one selected by the Captain:

- When the EFIS DMC selector switch is in the NORM position, the CAPT

PFD and ND are driven by the DMC1

- When the EFIS DMC selector switch is in the position 3, the CAPT PFD

and ND are driven by the DMC3

- when the EFIS DMC selector switch is in the position 2, the CAPT PFD and

ND are driven by the DMC2.

The same applies to the First Officer EFIS displays:

the active DMC which drives the F/O PFD and ND is the one manually

selected by the First Officer (NORM is DMC2, 3 is DMC3, 1 is DMC1).

(3) COPY mode

The COPY mode is the configuration in which the four EFIS displays are

driven by a single EFIS part of one valid DMC: -

-this copy mode takes place only when one single DMC is valid. When two

DMCs are

available, the CAPT side and the F/O side are driven independently to

keep the most redundant situation.

(4) EFIS REVERSE mode


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In some cases it is necessary to exchange the PFD and the ND. This is

the EFIS reverse mode.

Furthermore, a PFD/ND transfer occurs to satisfy priority of the PFD over

the ND.The PFD and ND are then exchanged.

The reverse mode takes place when the PFD DU is no more valid but the

ND DU is still valid.

The reverse mode can also occur on crew request.

When a reverse mode occurs automatically, the previous normal mode is

not automatically recovered if the PFD DU condition turns back to

normal. But, if the reverse mode is manually (or automatically)

requested, a new request reverts PFD/ND configuration to normal.

(6) ECAM REVERSE mode

In some cases it is necessary to exchange the EWD and the SD. This is the

ECAM reverse mode.

The ECAM reverse mode occurs automatically when the EWD DU is no

more

valid but the SD DU is still valid.

If the EWD DU becomes valid again, the normal mode is not

automatically recovered. It can be manually requested if the pilot

switches off the EWD DU and on again, or if he switches the DU to

another ECAM DMC.

(7) ECAM/ND transfer

This transfer enables to show one of the ECAM displays on one ND DU,

on crew request.

(8) ECAM single display mode

The single display mode occurs when only one DU is available to show

both ECAM displays.

In the single display mode the EWD is preferably displayed but a

system page is available when the crew push the related key on the

ECAM control panel.


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The single display mode takes place automatically when only one DU is

available for ECAM function. Then the EWD is displayed in priority on

the single DU and the SD is available on request.

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