Original Flight Hardware: INS Mode Select Unit (MSU)

Since the Lockheed L-1011 was/is a pre-GPS area aircraft, the navigation system in the L-1011 is based on an inertial navigation system (INS) only. So, basically, the MSU controls the application of power to the INS and controls the STBY, ALIGN, NAV and ATT modes of operation as indicated by the switch.



Here as a more detailed description of the modes:

STBY - Turns INS power on and selects standy mode. Pilot enters the present latitude and longitude and he or she may perform a display test. An automatic alignment sequence starts. The system is not affected by aircraft movement while in STBY.

ALIGN - Select alignment mode in which the system aligns automatically. The INS turns on the READY NAV annunciator when the automatic alignment is completed to indicate the the INS is ready for the pilot to switch to the NAV (navigate) mode of operation.
NAV - Select navigation mode. This it he normal flight operation mode of the system and must be selected prior to moving the aircraft.
ATT turns of navigation mode and the INS will provide attitude information only.



The READY NAV annunciator comes on in ALIGN mode to indicate that the alignment sequence is completed an the NAV mode can be selected.
The BAT annunciator comes on when the backup DC voltage is being used and is less than the minimum required to operate the INS.



Panel Locations