A380 Landing Gear
Vibes,
The bogie of the landing gear is positioned when the gear is extended by a pitch trimmer (hydraulic actuator). On the A330/340 a/c the Main (Wing) landing gears are tilted 'tail down' as they have a load carrying capability even when the front wheel are not on the ground - this improves takeoff performance. The B777-300 also has a similar but simpler system.
On the A380 there is no load carrying capacity when all wheel are not on the ground. The choice of positioning of the bogie for landing is usually made due to loads considerations - high loads occur as the wheels touch down and spin up due to gyroscopic forces.
I assume you are referring to the Body Landing gears on the A380 ? These are positioned 'nose down' for landing (by a pitch trimmer which is fully extended). On retraction this pitch trimmer retracts and positions the bogie 'nose up' so that the gear fits into the landing gear bay. Landing with the bogie 'nose up' is a failure case (of the pitch trimmer) which generates higher loads.