L-1011 Navigation: Model Selector Unit (INS) (34-43)

 The attitude position (ATT) disables the navigation computer but retains the platform for attitude reference.

There are two mechanical stops - one between the standby and align positions of the switch, and one between the NAV and ATT positions. To move the switch past the stop, the switch must be pulled up and rotated past the stop. Once the mode selector has been placed in the NAV position, it can be returned to the align position without dumping the program in the computer. However, if the switch is placed in either the standby or attitude positions, the program is cleared and the set must be realigned before it can be used for navigation.