A321 Slat Datum Zero
This afternoon, I was reading through the procedure to adjust the slat track closure doors on the A321. Part of the proceedure is to retract the slats manually to the "datum zero" position to adjust the closre doors in that position. However it does not explain what the datum zero position is. A word search of the AMM only to be referenced in 2 other places. Flap installation and slat 5 installation in memory serves me right.
Can anybody tell me if Datum Zero is the slats retracted using the slat rigging block at slat track 9? Or is it the slats retracted to the APPU reading taken before removing the drive shaft?