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Jumping T/D

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Hi,I've been having this problem from time to time : in cruise my T/D starts jumping e.g. 5nm before a VOR, then it changes to 5NM after a VOR, like it doesn't know where to start descend. And there are no altitude constrictions like "above x altitude"Anybody a clue why this happens ?

Did you input or changed any "DES FORECAST" winds ?Or did you get some wind change ?These 2 items may cause a "jump" in the T/D point.

  • Author

negative on the descend forecast. I do however run ActiveSky 2004, so that my produce windchanges enroute...

UM it is a little jumpy on PMDG's NG and winds etc will make it more pronouced. If it matters, I believe that pilots use the CLIMB page for TOC distance and not follow the actual TOC green marker on the ND although it is a visual reference point on the route... Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

Randy J Smith

  • Author

>> UM it is a little jumpy on PMDG's NG and winds etc will make>it more pronouced. What are you meaning by UM?If it matters, I believe that pilots use>the CLIMB page for TOC distance and not follow the actual TOC>green marker on the ND although it is a visual reference point>on the route...> I am not having problems with the TOC but with TOD. I am not comprehending what you mean by visual refernce point. I presume a visable point on the PFD ?

LOL sorry "UM" means that I am thinking, sorry I was not clear. TOC-TOD markers on the Navigation Display mean the same thing for what I am explaining to you since they both are effected by movement. T/D shown as a GREEN T/D on the magenta route on the Navigation Display. This will not always stay in the exact spot on the Navigation Display but will at times appear a little "jumpy" moving on the LINE and with weather etc will effect this "movement" even more. What I mean by visual reference point is that on the Navigation Display you have a dynamic visual map displayed and the T/D-T/C DECEL points shown on there give you a visual "idea" of where on your route you can expect the event to happen..Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

Randy J Smith

Hi,I'm using the AS2004 too (great great great add-on !) and sometimes I got a T/D jump when I fly in a new wind area. So I think that this could be a nice explanation.

  • Author

Thanks for the comments and help guys. I presume it must be related to AS2004 activity.

Another thing that I've noticed causing that is if the FMC crossing altitudes aren't set up properly on the legs page. For example you put a restriction on waypoint A of 250/7000ft, but waypoint B which is after waypoint A has a restriction of 315/FL190. Meaning that the FMC will have to descend to 7000ft then climb to FL190. That usually produces the jumping TOD circle. This can happen if the STAR has incorrect crossing restrictions set up. Changing the crossing restrictions generally corrects the jumping problem for me.That's 90% of my cases. The other 10% has to do with weather, specifically winds. In that case, the Jumping settles down when you get close. Mind you, I've only seen this about 4 or 5 times.

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