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(j)
A detected vertical speed failure is annunciated by removal of the digital readout and analog display and the appearance of a yellow boxed VERT where the analog display is normally located.
(k)
Selected barometric reference is displayed below the altitude tape full time as either a numeric value with units or as the letters STD for standard barometric reference (29.92 in. Hg). There are two display locations for barometric information, actual barometric reference used and preselected barometric reference to be used. Preselected barometric reference is displayed when standard (STD) is selected on the EFIS control panel for barometric reference used. When selected barometric reference is displayed, the units legend is IN. for inches-of-mercury or hPa for Hecto Pascals. The barometric reference display range is 22.0 to 32.0 inches-of-mercury or
745.0 to 1082.6 Hecto Pascals. A detected barometric reference failure is annunciated by removal of that display.
(5) Main and auxiliary EICAS displays
(a)
Air data system display presentation on the primary EICAS consists of total air temperature (TAT). TAT is displayed by a digital readout in degrees Celsius or degrees Farenheit including sign. When the readout indicates zero degrees, the sign is removed. A detected TAT failure is annunciated by removal of the digital readout including sign and units.
(b)
Air data system warning (red) and advisory (amber) messages are displayed on the primary EICAS. The latest occurrence message will appear on the top line of the display. An advisory message will follow a caution message if a caution message is displayed and a caution message will follow a warning message if a warning message is displayed.
(c)
Air data system status (white) messages are displayed on the secondary EICAS display. To bring up a status message on the secondary EICAS display, the STAT button on the EICAS display select panel must be pushed. Pushing the STAT button will bring up the latest occurrence status message.
(d)
A list of air data system EICAS messages are shown in Table 1.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
~............................................................. | TABLE 1 | | AIR DATA SYSTEM EICAS MESSAGES | ............................................................... | MESSAGE | TYPE | CAUSE | ............................................................... | ADC CENTER | STATUS | Center ADC failure | ............................................................... | ADC LEFT | STATUS | Left ADC failure | ............................................................... | ADC RIGHT | STATUS | Right ADC failure | ............................................................... | >OVERSPEED | WARNING | Airplane speed exceeds | | | | maximum operating speed | ............................................................... | P/S XFR VLV | STATUS | Pitot and/or static source| | | | select valve failed to | | | | transfer when commanded | ............................................................... | >SOURCE SELECT ADC | CAUTION | Both pilots using same | | | | ADC | 2.....................…...........…...........................1
K. Inertial Reference System (Ref 34-21-00)
(1)
Components of the inertial reference system that interface with the air data system are the:
(a)
Left inertial reference unit (L-IRU)
(b)
Center inertial reference unit (C-IRU)
(c)
Right inertial reference unit (R-IRU)
(2)
The inertial reference system receives digital data from the left and right ADCs on data bus No. 2 and data bus No. 4. The left ADC serves as the primary source for the left and center IRUs and the alternate source for the right IRU. The right ADC serves as the primary source for the right IRU and the alternate for the left and center IRUs.
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