What's the difference between the two, Fail Passive and Fail Operational?

[Guest]

Can anyone explain the difference between Fail Operational and Fail Passive?Thanks..........

[Guest HPSOV]

Fail Operational- Land 3. Where you have 3 autopilots engaged, such that any single failure will result in the remaining 2 autopilots being able to safely land the aircraft. Ie if there is a failure autoland remains operational.Fail Passive- Land 2. Where you have 2 autopilots engaged, such that a single autopilot failure will result in the disengagement of both autopilots with no significant deviation from the established flight path. In this case the pilot must manually take control and go-around/land.For Land 2 operations you are restricted to CatII minima, or 100ft, which also happens to be the minimum altitude from which it is recommended you are able to disconnect an autopilot and manually land. For Land 3 operations below alert height (100ft <-- may be a company specific figure) it is considered safe to continue to an autoland to CatIII minima in the event of a single failure. The design safety factor is 1 in 10000000, which is considerably better than the proven safety factor for manual landings (ie the chance of autoland pranging, even after a single failure is less than the chance of a pilot manually flying).

[Guest Mark McG]

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