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VNAV blues : problem identified + normal disconnect conditions

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Thanks Anthony and Vangelis. Sounds good!If I remember right: Don`t pour water onto those Gremlins :)

Ah yes... well somebody gave water to our Mogwai.... after midnight...;-)Now we have a gremlin, we're double careful !Anthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Just to give you an idea :- Started descent about 60nm from rwn extension, from a cruize alt of FL220- I was above the standard decel segment and reviewing the legs page I noticed I was going to arrive to rnw extension at 240kias, too high- I input on the legs page a restriction on rnw extension of 170/2000 and execed. I was about 40 nms out.- this resulted (I checked the maths) in a current deviation of +- 2000 HI, because the decel at rnw extension implied a shallow decel segment - about 8nm-, before resuming angle from there to 10000...- 2000 HI is a lot, and might result because the AC will try to compensate for it in an overspeed...Soooooooooooooooo, it is best, as in real life, to plan descents carefully nad in advance if you intend to use VNAV PTH ;-)anthonyPS (edit) : when approaching TOD, if you do some amendments to FP - such as choosing a star or defining an alt constraint on a downstream wpt -, this might result in the TOD being computed behing the aircraft, and the current phase go to descent at change execution. This was not taken care of, now it is !Anthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

I agree I have to plan my TOD/TOC better, it helps a lot. I tried a FSBuild2 fp from KSFO to KLAX yesterday. Loading it into the FMC, I noticed the TOC were far away from the mangenta line, on the opposite side in th ND, all alone. But fixing it was easy, the first waypoint was too close for FL350, so I changed it to FL250, executed, and the TOC ring suddenly popped into the right place :)Aslo I have found out it is important to look through all the waypoints on the LEGS page. Often I find one or two with altitudes lower than the CRZ level. A few edits and I`m ready to fly VNAV!

Ah ! can you mail me the FSBUILD produced FP without changing it ? I'd like to check something in it. [email protected] MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Hi Anthony,Just sent you the flightplan, both original and modified. Well the climb is a bit steep still, but I blame that on my sloppy planning :)

I was curious and went for a new test...The same plan was exported from FSBuild with the option "Export TOC/TOD", and FL410. Loaded the plan into the FMC, finished INIT REF where I set CRZ ALT=FL410. Again I got the offset TOC in the ND, like in the attached picture. Checking the LEGS page, I had lost ALT for the waypoints Wages and Ave. For who knows what reason I checked the CRZ page, and the level was zero. I set FL350, and that fixed Wages and Ave, got FL350. Seems the FMC doesn`t like levels higher than FL350? Like before, I fixed TOC by setting WP Wages to FL250. Last thing I discovered on the LEGS page was WP Reyes=1950ft or so. A bit low, as the next WP was FL100 I think...I`m not yet finished editing the flightplan, don`t know if it`s more Gremlins lurking around!

Hmm, had this too when loading the FP (all predictions ok now, BTW).Setting dep runway corrected this. I'll check this and fix it.It should not happen... Where's my other Mogwai ?anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Hi Anthony,The fresh, untouched fp I just sent you is made with build 132 (beta). I don`t know if that has anything to do with this, but I don`suspect that. But I know it is important to check out the plan before exporting. Personally I like to edit it in the FMC and then re-save it. Today, I`ll try to enter the plan manually, based on the FSBuild log file, and see what happens then.Regarding the Mogwai, don`t bring the flightbag with you ;)

'lo againThe TOC problem :the FP exports dep runway 25L which is not recognized by the AIRAC data, so the FMC resets the runway to none, but it forgot (!) to reset the runway position as well, and used the latter for calculations.Fixed now. Position reset if runway unavailable.cheersAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

will be 290 for descents as well.Anthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Yes, I had the same experience first time I used this plan. I entered KSFO on the RTE page, then I loaded the fp and executed. On the DEPARR page, I got no reaction clicking the KSFOKLAX LSK buttons. So I had to enter KSFO manually as the DEPORIGIN airport, that helped. I have experienced this situation with several plans. The FMC says "Not in Database" when I enter the fp, but I ignore the message, and are still able to exec the flightplan. Sometimes the runways are not listed. The I just enter one of the rwy directions (like 19L), and suddenly I get all the data...hmm, I wonder if slapping the FMC hard with my hand helps? :)

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