Can someone tell me what I'm doing wrong...?

[Guest]

I seem to remember another PMDG user had a similar problem to mine but I cannot find the thread for it. Well, anyway here's an issue which I'm 100% sure is my own fault but I can't figure out what it is im doing wrong.And, yes it's VNAV related!! Ok, so I'm cruising at FL310, I reach my T/D point, so I open my FMC, go to DES, select Path Speed Des and then I hit DES NOW...the speed is set for 290kts and below 10000ft it's set for 240kts.Ok, after I hit DES NOW things appear to be ok for the moment. My vertical speed drops to around 2000fpm. After a bit, I get a msg on the FMC which states "Autospeed disconnect" and an icon appears in my PFD in yellow "CWS" The plane then proceeds to pitch up and climbs about 1000ft and then descends at a rate which would make every person on board simply pass out...something like -9000fpm!!!So, a flight that had previously been wonderful has just been turned into chaos simply by using VNAV. I know the darned system is a huge source of frustration for virtual pilots and real-world pilots but I'm quite sure no one is dropping like a stone out of the sky like I seem to be!Any words of wisdom greatly appreciated.RegardsChuck Nevin

[Guest whites]

I don't know about the problem your having though it sounds a bit nasyt :-) but, to begin a decent at T/D just set the MCP to a lower altitude before reaching the T/D, the 737 will begin decending all by itself after crossing the top of decent.Maybe a speed decent is for loss of cabin pressure so that why it's decending so fast :-) Don't level out too quick though and leave the wings behind! The autothrottle disconnect might be because at that decent rate the aircraft can't control the speed so it figures you know what your doing so it will let you have control :-)Steven.

[crvm 0]

It's because you need to CONTROL the overspeed that is happening, in other words USE THE SPD BRAKE! WHen that happens you can do a few things to get it back, hit ALT HLD for a moment and dial in the target descent speed, once the bird slows to the target reengage VNAV. Remember that a SPD DES will not follow any PATH but pitches for target des spd only. [h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-8/196432/winglets_lg.jpg [h3] AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h3]

[Guest]

Cool, I'm going to go try again right now.Thxchuck nevin

[crvm 0]

Great, you should try to keep it within 10 knots if at all possible, as long as you have the spd brake going you should be able to keep it within the range so it will not disconnect, if I recall it's 20 knots over the target that it will disingage, real bird I think is 15 knots...[h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-8/196432/winglets_lg.jpg [h3] AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h3]