interesting problem with VNAV using saved flightplans

[Haukeland]

I have now used the updated 737 in FS 2002 a lot of days with flawless VNAV function. I saved a few flightplans in the FMC and could flight them without any problems. Than I saved some more planes and stored them -again only the routes without any settings on PERF page - and took a test flight:
I engage VNAV and LNAV at about 1000 AGL. Flaps up at 186 kn. At about 6000 ft VNAV suddenly disengages and the aircraft continues climbing with SPD engaged but no visible VS. I have not done anything before that occurs. The only way to reengage VNAV is to change altitude on MCP slightly and than to press the VNAV button again. Than the aicraft climbs as usual. This behaviour is present with FSUIC on or off, I have a normal VNAV climb when making a flight plan in the FMC and not using the stored ones. I see the problem both in FS 2000 and 2002. I transferred some newly stored flightplans from the FS 2000 FMC database to FS 2002.
Anyone who can help me with this?

[Palle]

Same problems here ! I hade just a few FLT-plans saved and they worked great. After saving a couple more flightplans my old ones stoped working properly. Problems vid VNAV and so on. After reading this messages i deleted all my flightplans and entered in a new one , saved it and load it again and now everything works.This sound verry verry strange i know, but i cant find any other reason why it starts working again.I will try to save more and more flt-plans to se if it happens again.

Lennart

[Tom_Main]

Hi Guys,

It is not a problem with VNAV. The aircraft was gooing into a ALT ACQ state. What happens with a saved fmc plan is simple. The value in the MCP Altitude block at the time you save the flight is saved. Now when you reload, that value is the internal value we are working off of. If you do not change the value on the MCP, this is where you get the confusion.

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[Palle]

Hi Tom

So if i make some changes to the fligtplan during a flight and save it i get what i have on the CMD Alt block as an internal value (not vissble on the CMD)next time i load the flightplan ?

Lennart

[Tom_Main]

Lennart,

Unfortunatley yes. Nick does not have the MCP update with the saved values when the plan is loaded.

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[Palle]

Thank´s Tom

Your information about this will probably solve all my problems (with the FMC offcours) :)

Lennart

[Haukeland]

Thanks for your respons! The practical solution seems to be the following: First loading the flightplan, than choosing cruise altitude on MCP. This works for me.