Why do we have to perform a full ADIRS alignment between latitudes of 2 degrees North and South on the A320 family? In the latest FCOM revision under the preliminary cockpit preperation normal procedures chapter ADIRS alignment has been added. However most of the conditions remain the same except for a new line which has been added wherein a full ADIRS alignment has to be performed at airports where the latitude is within 2 degrees North and South.
Could anyone explain with a reference why Airbus has decided to add this ?
As per my company FCOM this is only applicable to certain MSNs (mainly our newest A320-251N's)
SOP is modified to introduce a new condition to perform a complete IRS alignment during cockpit preparation. When departure airport is located between latitudes 2° north and 2° south, a full alignment must be done. This is to avoid excessive drift of Honeywell ADIRU Block III during the subsequent flight.