Maybe I'll have to get myself seriously updated on how a present-day Rad Alt works.
The 30°/60° tx/rx cone makes some sense, but I would still have thought the RA would "lock on" to the first return, which would be from straight down below the aircraft (unless you were 200 ft off the Rock of Gibraltar).
"Old Boffin"
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Edit
The radio altimeter receives information from:
a) The ground within an ellipse of 30 degrees in the for and aft axis and 60 degrees in the athwartships axis beneath the aircraft
The venom seems to be in the head, rather than the tail:
"...receives information from..."
Considering the typical RA aerial pattern, this is probably true.
It then should be capable (and presumably is), to process this information sufficiently to display the height ABOVE GROUND of the aircraft, even if the aircraft is not horizontal, either in pitch or roll.
Anybody has a straightforward answer? Or do I have to go and dive into ancient literature, or (heaven forbid) Google?