Distance Measuring Equipment (DME)
(1)
The DME interrogators provide distance information to the FMC, through the DAA. When manual tuning is selected on the VHF navigation control panel, a manually selected DME frequency is tuned. If automatic tuning is selected the DME interrogators are tuned by signals from the FMC.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
(2)
When automatic tuning is selected, station selection is determined by the FMC, using navigation information and station geometry information. In the event that one of the DME interrogators is manually tuned to a station that does not satisfy the range and geometry of the FMC, (or if one of the DME interrogators fail); the FMC will automatically place the remaining DME interrogator in a frequency agility mode, provided automatic tuning has been selected. This remaining DME interrogator will be automatically tuned, (at five-second intervals), between two DME stations. Two DME stations, however, must be available that satisfy the range and geometry criteria of the FMC. Agility tuning allows DME/DME position determination with a single DME.
VHF Navigation Receivers
(1)
The VHF navigation receivers provide deviation and bearing information to the FMC, through the DAA. When manual tuning is selected on the VHF navigation control panel, a manually selected VHF frequency is tuned. If automatic tuning is selected, the VHF navigation receivers are tuned by signals from the FMC, and station selection is determined by the FMC, using navigation and station geometry information.
Fuel Quantity
(1)
The fuel summation unit processes and sums signals from individual fuel tank indicators, to determine total fuel. The summation unit provides this total fuel information to the FMC, through the DAA.
Inertial Reference System (IRS)
(1)
The IRS is the primary component on the airplane for attitude measurement, and position determining. The IRS utilizes a ring laser as its means of inertial reference. Each IRS provides present position, heading, attitude, velocity, altitude, ground speed, and vertical speed to the FMC; through an ARINC 429 high-speed Digital Information Transfer System (DITS).
(2)
An output ARINC 429 channel from the FMS allows the user to initialize the IRS on the ground through the CDU by entering the airplane present position latitude and longitude values.
Digital Air Data Computer System (DADC)
(1)
Two DADC interface with the FMC. The DADC system provides altitude, DADC, airspeed, mach, and temperature information to the FMC, through an ARINC 429 low-speed DITS.
Clock
(1)
The clock provides an output of Greenwich Mean Time (GMT), or GMT and date (if GMT and date clock is installed) to the FMC. This interface is in accordance with ARINC 429 low-speed DITS.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
(2)
The captain's clock supplies clock data to the left FMC. The left FMC supplies the clock data to the right FMC on FMC bus 18. The first officers clock supplies the clock data to the FMCs when the captains clock is not valid, or when the FMC SOURCE SELECT SWITCH is in the BOTH ON R position when power is supplied. The right FMC then supplies the left FMC the clock data.
Discrete Signals
(1)
The FMC accepts discrete input signals from wing anti-ice, engine anti-ice, and engine bleed systems. These systems when activated cause an engine thrust reduction. The FMC uses these discrete signals to provide corresponding reductions to calculated performance values.
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