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MAINTENANCE MANUAL
POSITION VELOCITY (IRS)
SENSOR DATA
CREW INPUTS
THROUGH CDU
KEYBOARD
INTER
SYSTEM
BUS
VHF RADIO
TUNING
COMMANDS
OFFSIDE FMC
FLIGHT MANAGEMENT COMPUTER
FMC Functional Diagram
Figure 2
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E. FMC Interface (Fig. 3 and 4)
(1)
General
(a) All digital bus inputs and outputs of the FMC will be formatted in accordance with ARINC 429 specifications.
(2)
Clocks (Fig. 5)
(a) Clock data is received from three sources: the MMRs, the Captain's clock, and the First Officer's clock. If the GPS ENABLE option is selected, the FMCs receive UTC clock data from both MMRs. The CAPT's clock supplies data directly to the left FMC and the F/O's clock supplies data directly to the right FMC. The intersystem bus sends data from each clock (CAPT or F/O) to the other FMC. Both FMCs normally use the UTC clock data from the MMRs. If valid clock data is not received from the MMRs, the FMCs will use data from the CAPT's or F/O's clock.
(3)
Central Maintenance Computer (CMC) (Fig. 6)
(a) The CMC logs and reports faults within the FMC. The CMC sends the date, time and test command word which initiates the FMC's Bilt In Test Equipment (BITE). The FMC performs its own fault detection tests. These tests can be initiated through the CMC or by pressing the self-test button on the front panel of the FMC. Any faults resulting from the BITE will be stored in the CMC via the EIUs for future reference. The FMC receives the test command word over a low speed digital bus.
(4)
Fuel Quantity System (FQS) (Fig. 7)
(a) Each FMC will receive data from one fuel quantity computer. This data consists of total fuel quantity and is calculated by the FQS through integration of the fuel flow. The data is received over a low speed digital bus.
(5)
Weight and Balance (W&B) (Fig. 7)
(a)
The W&B computer calculates the airplane's center of gravity and gross weight. It sends this information over a low speed digital bus to the FMC.
(b)
The airplanes gross weight, calculated by the W&B will be displayed on the PERF INIT page on the CDUs. The W&B calculated gross weight can be used for FMC initialization if valid or the pilot can enter a gross weight using the CDU keyboard.
(6)
Airborne Condition Monitoring System (ACMS) (Fig. 8)
(a) The ACMS receives engine related data from the FMC for purposes of recording. This data is transmitted over a low speed digital bus.
(7)
Modularized Avionics and Warning Electronics Assembly (MAWEA) (Fig. 8)
(a) The MAWEA provides aural warnings for crew alerting of unsafe or abnormal flight conditions. The FMC transmits minimum buffet speed and autothrottle status over a low speed digital bus.
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(8)
Cockpit Pressure Control System (CPCS) (Fig. 9)
(a)
The FMC transmits the following data for cockpit pressure control. 1) Time for climb 2) Time for descent 3) Time to touchdown 4) Cruise altitude 5) Landing altitude 6) Autothrottle mode 7) VNAV mode 8) FMC master
(b)
This data is transmitted via a low speed digital bus.
(9)
Ground Proximity Warning Computer (GPWC) (Fig. 9)
(a) The FMC transmits track angle, magnetic heading and present latitude and longitude position to be used for calculations in the GPWC. This data is transmitted over a low speed digital bus. 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(115)
