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Another question's answers refer to certain Boeing jets having the capability to annunciate "Land 2" and "Land 3" when flying a coupled ILS approach. What does each of these modes require, and allow, beyond the basic coupled ILS? How are they different from one another?

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From "Smart Cockpit"

B777 Automatic Flight (PDF!)

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AFDS Status Annunciation
The following AFDS status annunciations are displayed just above the PFD attitude display:
• FLT DIR (the flight director is ON and the autopilots are not engaged)
• A/P (the autopilots are engaged)
• LAND 3 (three autopilots are engaged and operating normally for an automatic landing)
• LAND 2 (AFDS redundancy is reduced; in some cases, only two autopilots are available)
• NO AUTOLAND (the AFDS is unable to make an automatic landing).

With a LAND 3 indication, the autopilot system level of redundancy is such that a single fault cannot prevent the autopilot system from making an automatic landing (fail operational).

With a LAND 2 indication, the level of redundancy is such that a single fault cannot cause a significant deviation from the flight path (fail passive).

An EICAS message is displayed for any fault which limits the capability of the automatic landing system. Aural alerts for EICAS messages not affecting safety of flight are inhibited until after touchdown. Changes in autoland status below 200 feet, other than a transition to NO AUTOLAND status, are inhibited.
From Chapter 9, pages 22-23

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    $\begingroup$ This is great information, but if at all possible please post text rather than images: searching won't find text information in an image. If that isn't possible here then adding a brief summary/explanation to the image would be a good alternative. $\endgroup$ – Pondlife Jan 3 '16 at 22:45
  • $\begingroup$ So, Land3 with all AP working, gives you Cat III autoland, right? And Land2 is good to, what, Cat II mins but you still have to make the landing? Is there a reason beside an A/P failure what you'd be in, or prefer to be in, Land2 instead of Land3? Are these modes needed for anything besides Cat II and Cat III mins? (Other than exercising the system, currency, etc.) $\endgroup$ – Ralph J Jan 4 '16 at 4:04
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    $\begingroup$ Land 2 is still good for a Cat III Autotland but with a Decision Height of 50'. There are numerous other equipment failures that can cause Land 2 status. (Autothrottle, Pitot heat, ILS receiver,Hydraulics etc). $\endgroup$ – Mike Sowsun Jan 4 '16 at 12:33
  • $\begingroup$ There is very little correlation with the Land 3 and CAT III. $\endgroup$ – Burhan Khalid Jun 22 '16 at 18:11

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