(14)
Continuously self-tests fuel quantity channel boards and processor I/O boards, and indicates if any board has failed.
(15)
Calculates the uplift fuel quantity and fuel density for display on the EICAS fuel maintenance page (AMM 28-21-00/001).
D.
Operation of the processor is controlled by printed circuit boards, located behind the hinged cover on the front of the processor. One individual fuel quantity channel (IFQC) board is installed for each fuel tank (except the horizontal stabilizer tank). Two input/output (I/O) boards are installed. Operational status of a board is checked by observing its LED indicator light, which is visible through the window on the processor cover. If the LED is green, the board is operational. If the LED is red, the board is faulty. If the LED is not illuminated, a power failure exists.
(1)
Each IFQC board uses inputs from the tank units, compensator, and densitometer, along with tank profile data stored on the board, to compute the fuel volume and fuel mass for its tank.
(a)
Each board uses an INTEL microprocessor as the central processing unit. Memory provisions include read-only memory (ROM) for program storage and tank profile data, and random access memory (RAM) for scratchpad functions.
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(2)
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(b)
Other board inputs include test commands from the I/O boards, the setting of the associated volumetric shutoff adjustment potentiometer, and data pertaining to airplane configuration and status (calibration units, presence of engine dry bay, airplane on ground).
(c)
The board outputs data in digital format to the I/O boards. Data includes calculated fuel volume and mass, calculated fuel density, in-tank component parameters (capacitance, resistance), and fault messages.
(d)
The IFQC boards are all interchangeable, each board containing tank profile data for all tanks. The tank associated with a particular location in the board file is determined by the configuration of the tabs on the board receptacle.
The I/O boards are the interface between the IFQC boards and other components of the fuel quantity indicating system. The I/O boards also control the automatic shutoff feature and preselect feature of the pressure fueling system. For more information on the pressure fueling system, refer to AMM 28-21-00/001.
(a)
Each board uses an INTEL microprocessor as the central processing units. One CPU (I/O CPU) receives fuel tank data from the IFQC boards and computes total fuel quantity and density. It also controls the pressure fueling operation. The IOC transmits data to EICAS and the CMC through the ARINC 429 digital data bus, transmits fuel quantity data to the fueling quantity indicators, and controls the fuel quantity processor BITE. Memory provisions include read-only memory (ROM) for program storage, random access memory (RAM) for scratchpad functions, and non-volatile memory for preselected and uplifted fuel quantity storage and component fault data.
(b)
I/O board inputs include data from each IFQC board, indicator and system test commands, and processor BITE initiation commands from the CMC. The I/O boards also receive signals required to find the necessary fuel load and to control the pressure fueling operation. For more information on the pressure fueling system, refer to AMM 28-21-00/001.
(c)
If the secondary I/O board fails, normal processing continues and the failure is transmitted to the CMC on the ARINC 429 bus. If the primary I/O board fails, fuel quantity processing continues but the pressure fueling operation is inhibited.
(d)
The I/O boards are interchangeable.
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A
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