777 AIRCRAFT MAINTENANCE MANUAL
RA SYSTEM -RA ANTENNA
EFFECTIVITY BEJ ALL 34-33-00
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EFIS Control Panel
The EFIS control panel controls the radio minimums and resets the radio minimums alert. The radio minimums show on the captain and first officer PFDs. The left EFIS control panel controls the captain PFD. The right EFIS control panel controls the first officer PFD.
The RADIO/BARO MINS control has these three concentric controls:
*
Two-position rotary switch (minimums reference selector)
*
Three-position rotary switch which is spring loaded to center (minimums selector)
*
Radio minimums reset switch.
The flight crew uses the minimums reference selector to select either radio minimums or barometric minimums. Radio minimums is the same as decision height (DH). Barometric minimums is the same as minimum descent altitude (MDA).
When the flight crew selects a radio minimums value, the three-position rotary switch, which is spring loaded to center, adjusts the radio minimums between -1 foot and +999 feet.
The flight crew pushes the reset switch to reset the radio minimums alert.
EFFECTIVITY
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The barometric minimums function does not relate to the radio altimeter operation.
PFD
The PFD shows radio altitude and radio minimums values. The flight crew uses this data during approach and landing.
Radio altitude shows digitally for altitudes between -20 and 2500 feet. The display updates in:
*
Two foot increments from -20 to 100 feet
*
Ten foot increments from 100 to 500 feet
*
Twenty foot increments from 500 to 2500 feet.
The display goes out of view above 2500 feet.
Radio minimums show on the PFD. The radio minimums display has the letters RADIO (radio minimums) and the radio minimums value. If the radio minimums value is less than zero feet or more than 999 feet, the display goes out of view.
Radio Minimums Alert
This happens as the airplane descends through the radio minimums value:
*
Radio altitude display changes from white to yellow
*
Green letters RADIO and the radio minimums value below it change from green to yellow.
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* Radio altitude, the letters RADIO, and the radio minimums value blinks three times at a 4Hz rate.
Each of these resets the radio minimums alert:
*
Push the radio minimums reset (RST) switch on the EFIS control panel
*
Airplane climbs to 75 feet above the radio minimums value
*
Radio minimums alert resets automatically at touchdown.
Reset causes the radio minimums value to go back to green and the radio altitude to go back to white.
RA Data Invalid
Invalid RA data causes a yellow RA flag to show in place of the radio altitude. The invalid occurs when the RA transceiver detects a failure in the RA system.
Radio Minimums Data Invalid or NCD
Invalid or NCD EFIS control panel data causes the letters RADIO and the radio minimums value to go out of view. The invalid occurs when the EFIS control panel, the onside CDU, and the center CDU fail.
RA Display Priority
The flight crew cannot manually select a radio altimeter for the PFD. When an RA transceiver fails, the AIMS selects another transceiver to show on the PFD. The selection priority shows below. A RA yellow flag shows on the PFDs only when all radio altimeters fail.
AIMS priority selection of PFD RA display:
Captain PFD L, C, R
First Officer PFD R, C, L
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Purpose
In addition to the EFIS control panels, the flight crew can use the CDUs to select a radio minimums value and to reset a radio minimums alert. When the flight crew uses the CDU, the onside EFIS control panel does not operate.
Operation
The captain selects a radio minimums value on the left CDU. The captain’s radio minimums show on the captain’s PFD. The first officer selects a radio minimums value on the right CDU. The first officer’s radio minimums show on the first officer’s PFD.
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