B737NG LAND 3 Sources

[mmrassi]

Hello Everyone,

In description regarding LAND3 in FCOM, It states that 2 A/P and 3 inertial sources are operating normally.

Can someone tell me what are these three "Inertial Sources" ?
And does "Land 2" mean that the failuer happened in one of those 3 inertial sources or it may also include A/Ps?

Thanks

[STBYRUD]

The third inertial source is the ISFD. The other two are the IRSs. LAND 2 could mean an inertial source (interface) failure, an autopilot failure though would give you a NO AUTOLAND.