PPRuNe Forums - View Single Post - Different ETA ND/MCDU on Bus
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Old 13th September 2012 | 11:10
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nitpicker330
 
Joined: Jun 2009
Posts: 2,167
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From: Australia
Nope. ND simply works out current distance to waypoint at current G/S and gives you an ETA. Simple slide rule stuff.

FMGEC Is a bit smarter than that, it calculates the ETA using your Selected/managed profile ( CLB CRZ DES ) and uses the forecast winds you've entered PLUS it blends in actual winds to arrive at accurate ETA predictions for all down route waypoints including Dest.

Hence over long sectors ( 450 miles ) the ND and FMGEC Flt Pln ETA's for your active waypoint may be a lot different due to the current wind being different to the forecast up ahead of you.

Same on the Boeing's I've flown.

Last edited by nitpicker330; 13th September 2012 at 11:19.
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