A320 difference in predictions on FMGS/ND
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Greetings
The point I am taking about is the NEXT WAYPOINT, displayed on the ND versus the active leg.
For the JET case, as long as you are not yet within the jet stream it makes sense, the FMS is blending the wind using an actual wind much weaker therefore the wind average is far less that what it should be, and it affects your predictions, until you are within the jetstream then ...
The point I am taking about is the NEXT WAYPOINT, displayed on the ND versus the active leg.
For the JET case, as long as you are not yet within the jet stream it makes sense, the FMS is blending the wind using an actual wind much weaker therefore the wind average is far less that what it should be, and it affects your predictions, until you are within the jetstream then ...
Joined: Jan 2005
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From: W of 30W
Originally Posted by waren9
FCOM 1.31.45 indicates that current G/S only is used to give the ETA for the next waypoint shown on the ND
Best exemple is to take a first waypoint something like 200 NM after takeoff and look at the difference of ETA between ND and MCDU.
Take that reading early after takeoff when GS is still pretty low and the difference will not be counted in minutes ... but in minutes X 10
As soon as GS increases, difference shrinks.
Joined: Aug 2005
Posts: 37
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From: Malaysia
kijangnim,
I thought you said the difference is because of
So which is which now?!
The point I am taking about is the NEXT WAYPOINT, displayed on the ND versus the active leg.
For the JET case, as long as you are not yet within the jet stream it makes sense, the FMS is blending the wind using an actual wind much weaker therefore the wind average is far less that what it should be, and it affects your predictions, until you are within the jetstream then ...
For the JET case, as long as you are not yet within the jet stream it makes sense, the FMS is blending the wind using an actual wind much weaker therefore the wind average is far less that what it should be, and it affects your predictions, until you are within the jetstream then ...
and That wind is used to compute the waypoint displayed on the ND, but will use the distance based on the bearing between the aircraft position and the waypoint, whereas on the MCDU it is based on the active leg (which could be great circle, rhumb line, Arc ....)
