(14)
Navigation Display (ND) (Fig. 13)
(a) The FMC transmits navigation data to the navigation display. This data consists of data related to track, heading, wind speed and direction, ground speed, distance to go, estimated time of arrival, and data contained in the NDB. Data contained in the NDB consists of all waypoints, navaids, airports and their corresponding data. This data is transmitted over a high speed digital bus.
(15)
Auxilary Engine Indicating and Crew Alerting System (EICAS) (Fig. 13)
(a) The EICAS receives all data relating to engine parameters as well as thrust modes (T/O, CLB, CRZ CON and their corresponding derates). This data is transmitted via the EIU on a low speed digital bus. The EICAS is also hardwired to the high speed bus directly from the FMC. This is because the CRT which normally displays the EICAS format is also capable of displaying the ND format.
(16)
Electronic Interface Unit (EIU) (Fig. 13)
(a) All engine related data to and from the FMCs are routed through the EIUs. The FMC's built in test equipment reports all failures to the CMC via the EIUs.
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(b)
The FMC receives both low speed and high speed digital data from each EIU. The low speed data consists of the following: 1) Bleed discretes 2) Bleed discretes status 3) Engine fuel flow (all engines) 4) Left and right manifold pressure 5) Fuel jettison discrete 6) Select flap position 7) Stick shaker speed 8) Maximum operating speed
(c)
The high speed data consists of:
1) Thrust resolver angle (TRA)
2) EEC status
3) EPR actual
4) EPR command
5) EPR maximum
6) Exhaust gas temperature
7) Main oil temperature
(d)
The FMC transmits low speed digital data to each EIU. This data consists of all engine related data and data to be displayed on either the EFIS or EICAS. It also transmits an analog A/T caution signal.
(17)
EFIS Control Panel (Fig. 13)
(a)
The EFIS control panel (EFIS CP) enables display options in which the crew can select. These options consist of display modes, display range, additional display data, barometric units, decision height and minimum descent altitude.
(b)
The FMC uses these display options in order to format its data for display purposes. The data is transmitted over a low speed digital bus.
(18)
Inertial Reference System (IRS) (Fig. 14)
(a) The IRS supplies the primary navigational data. This data consists of the following: 1) Along track horizontal acceleration 2) Lateral acceleration 3) Normal acceleration 4) Cross track horizontal acceleration 5) East-West velocity 6) Flight path acceleration 7) Ground speed 8) Inertial altitude 9) Inertial vertical speed 10) IRS discretes 11) Magnetic heading 12) North-South velocity 13) Pitch angle 14) Present position - latitude and longitude
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15) Roll angle
16) Track angle true
17) True heading
18) Vertical acceleration
(b)
The FMC's navigation function uses mixed position and averaged velocity data from the three IRUs. The navigation function selects the IRU to be used for its primary data source as explained in the navigation computation function section.
(c)
The other FMC functions (Thrust and Guidance) follow the selection of the autopilot as the determining factor for the selection of data from the IRSs as follows: 1) The left IRU is the selected source data when one of the
following conditions is met.
a) No autopilot is engaged and neither flight director is
on b) Only the left autopilot is engaged c) The left autopilot was the first engaged autopilot in 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747-400 AMM 飞机维护手册 导航 NAVIGATION 3(117)
