"The fact that ATT does not work is either an oversight or shoddy programming. All it requires is to stop the part of the IRS software which updates the nav solution and clear down a few validity flags. "
As I understand it, Synthetic, IRU's will not give you an accurate ATTitude indication unless you are flying relatively straight and level for a certain period of time. Would a D level sim programmer have to model the IRU's to this sort of detail level (showing slight errors in attitude if the aircraft had not been flying straight and level). Or is this what you meant by "nav solution"?
A few years ago, I wanted to see what would happen on a real aircraft when selecting from OFF to ATT whilst in motion (to see what sort of displays I would get). I tried selecting ATT whilst an aircraft was being towed from one gate to another. During the period from selecting from OFF (to ATT) to the horizon appearing on the displays, the aircraft made a sharp right turn. As I recall, the attitude display took about about 45 seconds or more to appear. The displays, without motion, normally take about 30 seconds to appear, so the radical movement , I suspect, was confusing the IRS's. Disappointingly, the horizon showed no abnormalities when it did appear (I was hoping for a 45 degree tilt
) Perhaps IRS's in reality don't display a correct horizon unless you have been flying straight and level for some time?
Anyway, I think I'm moving a bit off topic here, so...
Cheers.
Q.