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747-400 dual FMC fail.

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747-400 dual FMC fail.

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Old 1st Sep 2022, 08:14
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747-400 dual FMC fail.

Just wondering If dual FMC fail. Is L-NAV function still available ?
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Old 1st Sep 2022, 21:49
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LNAV is not available in the case of dual FMC failure. (Most) active RTE legs are retained by the CDU alternate navigation function at the time of failure and will display on the respective ND. However no steering commands are generated so you'd have to fly it in HDG SEL or similar.
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Old 2nd Sep 2022, 09:41
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If we can only use HDG mode to track the route displayed on ND, are we still meet the RNP10 requirement?
personally, I think if we lost both FMC. we lost RNAV capability and eventually, we are not able to meet the requirement.
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Old 2nd Sep 2022, 14:36
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At least 1 FMC is required for RNP 10.
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Old 2nd Sep 2022, 15:50
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You do however retain Cat3 No DH Autoland capability.
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