EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
34-33-00
ALL ú ú 07 Page 5 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
H17053
A
747-400
MAINTENANCE MANUAL
C. EFIS Control Panel (DH Related Functions)
(1)
The EFIS control panel provides selection of the decision height (DH). DH can be selected from -20 to +999 feet by turning the DH SELECT knob. DH numerical value selection and status appears on the pilots' primary flight displays (PFD). If the control panel DH and RST (reset) functions fail, these functions may be set and reset at the pilots' control data units (CDUs). The RST switch terminates DH alert when it is pushed and allows selection of a new DH value. (Ref 34-22-00).
(2)
The EFIS control panels are located on the pilots' glare shield P10.
D. Primary Flight Display (PFD) (Radio Altimeter and Decision Height (DH) Related Functions)
(1)
Radio altitude and DH data is displayed just above the airplane symbol/attitude reference section of the pilots' primary flight displays (Fig. 1). This data is used mainly during approach, landing, and climbout.
(2)
Radio altitude is displayed only for altitudes between -20 and 2500 feet. From -20 to 100 feet the display updates in 2-foot increments, between 100 and 500 feet the display updates in 10-foot increments, and from 500 to 2500 feet the display updates in 20-foot increments. Above 2500 feet the display is blank.
(3)
Decision height is displayed above the radio altitude. If DH selected is negative, the display is blank. Decision height alert is armed when the airplane descends through an altitude of 75 feet above the selected decision height. Arming does not result in a display at the PFDs, but will result in a DH alert audio signal to the pilots' interphone panels, if connected.
(4)
As the airplane descends through the selected decision height value, radio altitude readout changes from white to yellow, and the green decision height numerical display above the radio altitude changes to large yellow letters DH. During the first 3 seconds the letters DH blink to alert the pilots that the airplane has descended to the selected DH altitude.
(5)
The DH alert at a primary flight display can be reset by:
(a)
Pressing RST (reset) pushbutton switch at associated EFIS control panel.
(b)
Ascending to a height 75 feet above selected decision height.
(c)
When reset, letters DH and DH numerical readout return to normal green display and RA readout returns to white.
(6)
Radio altitude fault indication at primary flight display.
(a)
Invalid RA data is indicated by yellow letters RA enclosed in a yellow box (flag).
(b)
If RA is equal to or less than 2500 feet invalid DH data is indicated by yellow letters DH enclosed in a yellow box (flag). If RA is greater than 2500 feet and DH is invalid, the DH display is blank.
(7)
Radio altitude No Computed Data (NCD) at primary flight display:
(a)
RA NCD is indicated by blank RA display when airplane is above 2500 feet. If airplane is below 2500 feet, radio altitude (RA) NCD is indicated as yellow letters RA in a yellow box (flag).
(b)
DH NCD is indicated by yellow letters DH flag display.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
34-33-00
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A
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