"When you select ATT, you will 'deactivate' the accelerometer, thus losing your NAV mode. In ATT, the gyros still supply info to your EFIS."
This is the part I have difficulty with... The manual states that:
"If alignment is lost in flight.... attitude information can be obtained by moving the selector to ATT. The IRU enters align mode for 30 seconds. This relevels the system and provides attitude displays on the PFD. For best accuracy, the aircraft must be in straight and level flight. Some attitude errors may occur during acceleration. After acceleration, errors are slowly removed"
If releveling and accuracy are affected by acceleration, then doesn't this mean that the acceleration is being measured? Doesn't attitude need some kind of earth centre sensing(like your old fashioned spinning gyros)...to know which way is down? Surely the accelerometers in the IRU's would perform this function?
Thanks.
Cheers.
Q.