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Guest cobalt60

Position locater

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Hi I noticed that the position indicator on the 744F is made of several chars any idea how to fix this???

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a bit vague, your question is. what is "chars". and who is this?max

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I get three *** and another >-< which I assume is the correct one. The *'s are not aligned and seem to be a error in the latest update.

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Hi,The * symbols are the position indicators derived from the three IRS units. The >o< symbol is the GPS data derived position (looks like a satellite).They (the *'s) will drift with the IRS drift - I guess pmdg modelled this.The GPS will usually stay dead on the nose though.Cheers,David

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To the best of my knowledge you will only see the drift after a pretty long swim across the pond. Back when a friend of mine used to fly MD-11s which were not GPS-equipped (only IRS units and navradios), he said after a long flight across the pacific, as the nav-radios started picking the VOR stations the plane would start banking erractly on its own every now and then as it triangulated its true geographic position from the stations since the IRS units had drifted considerably. Best Regards,Victor Limahttp://www.precisionmanuals.com/images/forum/800driver.jpg

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"To the best of my knowledge you will only see the drift after a pretty long swim across the pond."They do drift in real life sitting at the gate and during taxy to the runway for T/O. In 30 minutes, I've seen as much as 0.5nm drift. This is probably why, pre-GPS, the FMC position was updated when you pushed a TOGA switch.Realistic drift levels are modelled in the 744F (more realistically than the pax).The symbols represent raw data (before they are averaged and processed to produce an more accurate FMC present position).Hope this helps.Cheers.Q>

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IRS's can't be updated when the aircraft is in motion (which it will be when the pilots push TOGA). Only the FMC position can be updated.I was oversimplifying with my TOGA updating statement....If GPS's are not functioning(or perhaps inhibited), then yes, I would agree with you that TOGA updating (for the FMC) would still be available. GPS inhibits TOGA updating.. at least on the 744. Cheers.Q>

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There is a difference between IRU position and FMC position.On the 777, the FMC position is checked between IRU/GPS and VOR-DME and updated when errors are detected.THE IRU position is only updated when the aircraft is stationary in align mode.I have seen a significant error in FMC position when a bad VOR/DME is autotuned. When VOR/DME is priority, position will shift and be wrong until a good VOR/DME is autotuned - or - you manually disable the bad VOR/DME.This happened often in Canada early in the 777 days - but was corrected in later system updates. In later years it almost never happens.As was indicated in a previous post - after a long time over water, even with GPS updating, when you get close enough to land that a radio signal is received, the FMC position will update. This "could" cause a brief track change but it is usually insignificant.---leo---

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