The passenger versions of the A330 have a small but noticeable nose-down angle when sitting on the ground:
In contrast, A330s built as freighters have a noticeable bump under the nose,1 which allows the nose gear to be mounted low enough down that it reaches the ground with the aircraft sitting level:
I can think of some disadvantages of having a nose-down body angle on the ground:
- Boarding (and, to a lesser extent, deboarding) would be slowed down slightly by the passengers having to negotiate a sloped cabin floor (especially those having to drag very heavy pieces of luggage uphill in the process).
- Ground servicing of cabin equipment would be expected to be made somewhat trickier by the sloped floor (a galley cart or other rollable object inadvertently left unattended for a moment would roll away towards the cockpit, potentially causing damage or injury if it has a sufficient length of unobstructed aisle to get up to a good clip).
- The nose-down body angle tilts the aircraft forwards compared to the situation that would arise with a completely-level fuselage; this moves the aircraft's center of mass forwards, shifting more weight to the nose gear that would otherwise be carried by the main gear, and, thus:
- Requiring a heavier, more substantial nose gear than would otherwise be the case.
- Reducing the maximum braking force available from the main gear (and thereby increasing the aircraft's stopping distance).
- Slightly decreasing the aircraft's directional stability on the ground (ye olde wheelbarrowe effect).
Indeed, the vast majority of large airliners sit level on the ground, rather than nose-down, so why is the A330 different in this regard?
1: Freighter A330s converted from passenger aircraft have no such bump, as the aircraft's cargo-loading system is fully capable of dealing with the slight slope.