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What means Cruise/Cost Index LRC


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Long Range Cruise (LRC) is a setting you can enable in the FMS for VNAV Cruise.

I was interested in it when I came across it some years ago, about why would an airline want to use LRC over a specific Cost Index or what have you...the setting appears in FMS all along the Boeing line, even the 737 has LRC.

I asked a couple pilots about it and they both said the same thing, never in their time flying have they ever used LRC, and they too dont know why or when it would ever be used. It seems to be a dumbed down mode in the computer, I didnt get into details, but it seemed that it didnt take into consideration all the variables that using a cost index would , it is more of a 'preset' if anything, so thus airlines use Cost Index over the hard coded LRC, since they all seem to have their own algorithmic means of dispatching what CI to use depending on winds, the state of the greater airline schedule, fuel prices, flight length, and so on....

So I took this information and pretty much decided...if they real drivers dont bother with LRC, then why should I

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LRC is 99% of maximum range cruise. However, MRC is such a sensitive speed to fly, that any speed deviations gets you either on the back side of the thrust curve, or well ahead of the curve.

LRC is birth of the jet age.

Cost Index is current state of technology in commercial aviation. About the only time you fly constant mach is oceanically, or when required by an MEL/CDL.

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