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The passenger versions of the A330 have a small but noticeable nose-down angle when sitting on the ground:

roll, roll, roll towards the cockpit

(Image by contri at Flickr, via russavia at Wikimedia Commons.)

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:

thing that goes bump in the daytime

(Image originally by Ceecookie at Wikipedia, via Leptictidium at Wikimedia Commons; cropped and modified by me.)

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.

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  • $\begingroup$ I would assume that if the aircraft is designed to sit nose-down, they would design it to prevent the issues in your last point about center of gravity. $\endgroup$
    – fooot
    Nov 14, 2019 at 23:34
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    $\begingroup$ Cant answer your question but to add to the question.. the cabin floor also raises towards the rear of the aircraft. If you look at the window line just a bit forward of the last passenger door you will see a point where it slops upwards. $\endgroup$
    – Anilv
    Nov 15, 2019 at 0:41

1 Answer 1

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For one reason or another, the main gear was made longer that originally planned and it was decided to avoid the cost and weight also extending the nose gear to match. The nose down angle while rolling along the ground is no big deal one way or the other, except for looking bad and disconcerting passengers who wonder why the plane is tilted forward.

Lots of airplanes are like that, sometimes because of changes made during development, but more typically after fuselage stretches where the main gear had to be made longer to keep the extended tail off the ground during rotation (the flying pencil CRJ1000, which I used to be type rated on, feels like a backwards taildragger in that regard). Obviously, the freighter needs a level cabin floor for loading, hence the nose gear band-aid; for the passenger versions, it's not really necessary and the blister and extra structure to do all that is just ballast and drag, serving no useful purpose.

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    $\begingroup$ It does not seem to come from a stretched variant. All A330 variants (except the -200F) have a lower nose (see page 60ff. in this PDF). $\endgroup$
    – Bianfable
    Nov 15, 2019 at 7:59
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    $\begingroup$ I fail to see how it answers the question ("why..."). You may explicit and highlight this point in your answer $\endgroup$
    – Manu H
    Nov 15, 2019 at 8:58
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    $\begingroup$ I think this does answer the question. Main gear length is determined by the need for tail clearance at take-off and landing. Nose gear length can be anything you want (unless it's a freighter), and a shorter nose gear will be lighter, so relatively long aircraft end up with a nose down angle on the ground. $\endgroup$
    – Robin Bennett
    Nov 15, 2019 at 13:44
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    $\begingroup$ Edits made to flesh it out a bit. $\endgroup$
    – John K
    Nov 15, 2019 at 13:48

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