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Guest t288msd

Top of descent and VNAV

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Guest t288msd

I know there are some known problems with VNAV that are being investigated, but here's one that I'm having that may be unrelated.The scenario: ...Cruising at FL420 (high, I know, but I'm very light and its the optimum). ...1000nm from destination. ...CI of 35, econ cruise showing M0.818. ..A/T, LNAV and VNAV on. No speed showing in the IAS/Mach window of the MCP (using the econ sped from the VNAV screen)....Three remaining waypoints in the LEGs page: STT, 800nm from destn; CF30, 10 miles from the runway; and RW30, the runway. (No STARs in use)I decide to track DCT to CF30 so I click it on the LEGs page and then clicking STT to overwrite it, and then click EXEC. Everything works fine, STT disappears, the acft makes a small turn to the left towards CF30 but the acft slows to M0.712 and remains at that speed. I'm still 900nm from CF30. The top of descent disappears from the PROG page indicating we are past top of descent.Re-inserting STT brings the speed back up and re-instates the top of descent indication on the PROG page. Removing it again had the same effect. I reinstated STT, overflew it and everything went fine.If this is a known problem with top of descent calculations when removing the last 'at cruise' waypoint, fine. If not I'd appreciate it if you could have a quick look.cheersMatt

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Guest t288msd

I tested this once more and got the same problem. Not much of an issue at airports with STARs, but for those without, it can be an issue.rgdsMatt

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Guest t288msd

Thanks John. The arrival airport was Bermuda, TXKF.

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