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747-400
MAINTENANCE MANUAL
(b)
If the onside EFIS CPs fail, then the CDU operates as the EFIS/EICAS control panel. Direct data entry can be entered in through the CDUs EFIS control or EICAS control pages selected on the MENU page. Onside for the L-CDU is the left EFIS/EICAS control panel and the onside for the R-CDU is the right EFIS/EICAS control panel.
(c)
The data consists of the following: 1) Baro corrected HPA 2) Baro corrected INHG 3) Decision height - selected 4) Decision height selected - Derate 5) EFIS discretes 6) EICAS discretes 7) WXR range
(d)
This data is transmitted over a low speed ARINC 429 digital
bus.Weather (WX) radar (Fig. 25)
(a)
The EFIS control panel enables the operator to enter a WXR range. The display range selected is transmitted over a low speed ARINC 429 digital bus to the WX RADAR unit.
Air Data Computer (ADC) (Fig. 25)
(a)
While the CDU is being used as an alternate EFIS control panel the operator is allowed to choose the units in which the barometric pressure can be displayed. These units are Hecto-Pascal (HPA) or inches of mercury (INHG). This data is transmitted over a low speed ARINC 429 bus to be used by the ADC.
Electronic Interface Units (EIUs) (Fig. 25)
(a)
The CDU transmits EFIS control panel data to the EIUs. This data consists of all the options on the EFIS control page as well as the EICAS pages of the CDU when there has been a EFIS CP failure.
Airplane Condition Monitoring System (ACMS) (Fig. 24)
(a)
The center CDU receives a subsystem identifier and text transfer from the ACMS for display purposes. The CDU provides the capability of displaying faults and messages from various subsystems through the ACMS. This data will only be displayed on the center CDU. The bus input is a low speed ARINC 739
ARINC Communications Addressing and Reporting System (ACARS) (Fig. 24 and 25).
(a)
ACARS is used to transmit data to and from ground facilities while the airplane is on the ground or while airborne. The information transmitted consists of flight plan, predicted wind data, preflight data for take-off and a request for position. The initiation of data transfer can either be performed by the ground based station or by the pilot through the CDU. The data will be transmitted over an ARINC 739 low speed bus.
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MAINTENANCE MANUAL
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Flight Control Computer (FCC) (Fig. 26)
(a) The CDUs receives ILS tune inhibit discrete signals from each of the FCCs . The right CDU will receive a signal from the right FCC, the left CDU from the left FCC and the center CDU from the center FCC.
(10)
Inertial Reference System (IRS) (Fig. 23)
(a)
The IRUs will send the following data:
1) Along track horizontal acceleration
2) Lateral and longitudinal acceleration
3) Cross track horizontal acceleration
4) East-West velocity
5) Flight path acceleration
6) Ground speed
7) Inertial altitude
8) Inertial vertical speed
9) IRS discretes
10) Magnetic heading
11) North and south velocity
12) Pitch angle
13) Present position - latitude and longitude
14) Roll angle
15) True heading
16) Vertical acceleration
(b)
This data is transmitted over an ARINC 429 high speed bus.
(11)
Flight Management Computer (FMC) (Fig. 12)
(a)
The CDU provides pilot interface with the FMC. It allows the operator to enter initiation data, reference data and display desired information. The input data from the FMCs is as follows: 1) Display update 2) Flight plan 3) Frequency data 4) Initial word 5) Subsystem identification
(b)
The output data from the CDU consists of:
1) Keyboard select
2) CDU BITE data
3) CDU identifier
4) Barometric correction HPA or INHG
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