737NG FMC Descent Problem

[GAJ52 54]

I have just been flying online at FL280 in VNAV with a restriction to fly a particular waypoint FL260 or below, so I selected the relevent waypoint and added /260B which it accepted and also put FL100 in the A/P panel ALT window prior to the waypoint. With VNAV still selected nearing the waypoint it made no attempt to descend to be FL260 or below, just continued at FL280 ??Ant idea what may have gone wrong ?Glen

[cavaricooper 2,614]

Forgive my asking, but did you EXECute? There ought to have been a TOD point appear on the ND if you did........Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png| XP Pro SP3 | 2 x APC UPS | Coolermaster Stacker 830 SE | Gigabyte P35 DS3R | e8500 @ 4gHz | Tuniq Tower 120 | EVGA 8800GT 512MB | Creative X-Fi Fatal1ty | 2 x 1 GB Corsair XMS2 | 2 x 320GB WD Caviar RAID 0 | Corsair HX620W PS | CH Products Yoke-Pedals-Throttle Quadrant | Aerosoft 747MCP-EFIS-EICAS |

[onurksn 1]

Glen,Forgetting to EXEC would be the first thing in mind but descending from FL280 to FL260 could be done in less than a minute, the AP won't start descending until you're very close to the given waypoint especially if there is a headwind.Also, did you take a look at your VNAV indicator on the ND? repeat the same thing, or a similar situation see if it happens again.Regards

[GAJ52 54]

Carl / OnurThanks for your helpYes I did EXEC the selection, thats what brought my attention to the problem, the TOD 'green circle' was just past the waypoint in question. As I watched the aircraft sail past the waypoint at the wrong level I decided to turn VNAV off and do it the old fashion way.I will try it again and this time closely monitor the VNAV indicator.Glen

[Mats_J 2]

Glen,Next time you encounter this please pay attention to what is annunciated in the FMA (Flight Mode Annunciator). Or maybe you even remember what modes the AFDS (Automated Flight Director System) was in for the flight in question?Cheers,