Originally Posted by channel4
Therefore as i understand in emergencies when we need to calculate landing distance we use 'L/D Conf Full without AB' and then apply failure factor.
Not in "emergencies" but rather when you have an aircraft failure affecting your landing distance like one of those depicted in QRH 2.32.
Bomb on board, crew incapacitation, medical situation...could lead to declare an "emergency", but even though overweight landing is an abnormal operation, it must not be treated like an in-flight failure.
If time permits, FCOM 2.03.20 p2 (manual landing distance with autobrake) will give you a realistic actual landing distance in CONF3 + AUTO BRK regarding your scenario.