Emit
On the idea of using 5 degrees radar downtilt if all IRU's are lost:
From where does the radar get information of the whereabouts of the horizon?
(info that is needed to determine where 5 degrees below the horizon is).
My prior post, apparently unclearly, stated if IRU input to the WXR is lost, the WXR will continue to paint, but with reference to the fuselage: 0 pitch and 0 bank. The 5 degree downtilt I suggested would be in reference to the longitudinal and horizontal axes of the plane, rather than the IRU reported horizon.
Bank right, and you get more ground return on the right, and less on the left. Same for nose up/down.
I realize now I made a mistake in terminology on that post, unrelated to this question, so I will edit.
GB