Manual Input Of RNP and UNABLE RNP Message
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Manual Input Of RNP and UNABLE RNP Message
I've noticed whilst sitting at the gate, than I was unable to generate an ">UNABLE RNP" EICAS message (747-400) by manually entering an RNP smaller than the displayed ANP. I waited about a minute for the message to appear to see if there was a time delay for the message, but I imagine that you would want to see a message relating to this ASAP.
Would there be an air/ground inhibit on this message or something more specific? e.g. LNAV and/or VNAV arm/engage
Thanks.
Cheers
NSEU
Would there be an air/ground inhibit on this message or something more specific? e.g. LNAV and/or VNAV arm/engage
Thanks.
Cheers
NSEU
Last edited by NSEU; 12th Dec 2010 at 01:46.
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AFAIK the logic is inhibited on the ground after a certain software version - noticed that the ANP was exceeding 10 NM while the IRS were aligning the other day and the aircraft didnt say a thing. On another ship (with older software) it immediately complained (UNABLE RNP) when the IRSs were turned on for alignment...
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stbyrud:
Perhaps the newer software was RNP AR compliant, which has far more demanding performance requirements than "plain vanilla" RNP.
AFAIK the logic is inhibited on the ground after a certain software version - noticed that the ANP was exceeding 10 NM while the IRS were aligning the other day and the aircraft didnt say a thing. On another ship (with older software) it immediately complained (UNABLE RNP) when the IRSs were turned on for alignment...
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That might well be the case - the aircraft in question (with the newer software) also continously displays ANP and RNP in the ND and has the ANP deviation bars on the PFD...
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NSEU:
That is speculation on my part. A load with RNP AR capabilities replacing a load without those capabilities would tend to show sublte changes of the nature described.
Improved software without RNP AR capability would likely have improvements of some type.
Actually, I wasn't aware of the new "AR" software.
Improved software without RNP AR capability would likely have improvements of some type.
