# Tag Info

10

The quoted explanation about "fail operational" and "fail passive" is correct, in that "fail operational" means the system will continue to function after an failure, and "fail passive" means the system will not misbehave after an failure. The exact number of autopilots required to make this work, however, is debatable; and much depends on how you define it....

4

Definitions provided by the FAA can be found in AC 120-28D - Criteria for Approval of Category III Weather Minima for Takeoff, Landing, and Rollout. From the document we find for Fail Operational: 4.3.2. Fail Operational Category III Operations. A Fail Operational System is a system which after failure of any single component, is capable of completing ...

2

I don't think the quote you gave is correct. This might be the case for some aircraft (like the Boeing 777 with 3 autopilots), but not in general. A more general definition is: Autoland systems are normally designated Fail Operational or Fail Passive. A Fail Operational system must have at least two autopilots engaged for the approach. The failure ...

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