I am not in any position to offer an
answer to your question XV105, but may I offer a 'speculation'? I would hazard that the projection you highlight might be a Radio Altimeter aperture? It looks like a casting or even a forging and far too fancy for a drain. It seems to me the surface in which the aperture is 'machined', would be pretty much horizontal in the landing configuration and thus offer accurate height of the centre of gravity perhaps? Given that the cockpit would be many feet above that, it makes sense.
Errr..... I'll get me coat.
