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Two radio altimeters are installed in the A320. They measure the aircraft height above the ground accurately .

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There are no radio altimeter controls in the cockpit. Both radio altimeters come on automatically when AC power is applied to the aircraft.

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After a brief self test, the radio altimeters are in a standby mode during ground operations. They become active at lift-off and then operate continuously until touchdown.

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Radio height is always expressed as the number of feet between the bottom of the wheels and ground.Radio Altimeter data is supplied to several different users and is displayed on both PFD at all times below 2500 feet AGL.

FMGC

RADIO ALTIMETERDATA

GPWS

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Normally, Radio Altimeter 1 (RA1) height is displayed on the captain’s PFD and RA 2 on the First Officer’s PFD.

RADIO ALTIMETER2

RADIO ALTIMETER1

Captain’s side First officer’s side

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The radio altitude display on the PFD changes in color and size based on height above ground and / or proximity to the decision height..

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This color coded digital readout is coupled with a white ground indication line and a red ground ribbon on the Altimeter scale.

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The ground indication line and the red ground ribbon correspond to the raising ground level when the aircraft is descending.

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As the aircraft descends below approximately 500 feet AGL the red ribbon appears at the bottom of the altimeter scale and begins to move up.

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The white ground line moves from the bottom of the PFD towards the horizon.

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At touchdown, the ribbon is in the centre of the altitude readout and the white ground line is merged with the horizon, as shown. These are designed to be used as a ground reference during autoland operations.

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In addition to the visual indications, during approach, there is a synthetic voice for radio height announcement.

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Depending on individual airline requirements, auto call-out announcements are made at pre-determined radio-altimeter heights.Example, “FOUR HUNDRED” at four hundred feet radio altitude.These call-outs will be heard even if the loudspeakers are turned off.

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Definitive text :At pre-determined heights, the announcement will be heard through the loudspeakers, even when the loudspeakers are turned off.For example, at four hundred feet, a call out of “FOUR HUNDRED” is made.

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GLOSSARYAUDIO FCOM

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OPERATION

ECAM INDICATION

GENERAL