somehow lost VNAV mid flight

[MarkW 1,490]

Just in the last few hours of an atlantic crossing and I decided to load the Descent Forecast (flightplan from PFPX and weather from ASN).  After I did this all of the computed altitudes were blanked out and in the progress page the ETA and Fuel values were flashing.  I could never get them back and ended up manually working out my descent and using V/S.  Just wondering if this is normal behavior or some issue with my sim.  thanks.

[pcubine 143]

Just wondering if this is normal behavior or some issue with my sim. thanks.

It doesn't sound like normal behavior. I have requested and loaded descent forecasts hundreds of time and never seen this. Was there any message on the CDU prior to this happening? Like maybe VERT PATH FULL.

[spesimen 135]

a similar topic was posted some time ago  and it turned out it was because of a speed/altitude restriction in the STAR that was not possible to meet in conjunction with the updated econ descent speed. for example the STAR required 280 and the calculated econ descent was 330.

modifying the descent speed on the vnav page to something like 280 made it all work again.

 

maybe when you updated the forecast it modified your descent speed to an unusable value such as this.

 

the thread was here; http://www.avsim.com/topic/495968-vnav-disconnect-flying-the-coorz3-out-of-kden/

 

cheers!

-andy crosby

[MarkW 1,490]

a similar topic was posted some time ago  and it turned out it was because of a speed/altitude restriction in the STAR that was not possible to meet in conjunction with the updated econ descent speed. for example the STAR required 280 and the calculated econ descent was 330.

modifying the descent speed on the vnav page to something like 280 made it all work again.

 

maybe when you updated the forecast it modified your descent speed to an unusable value such as this.

 

the thread was here; http://www.avsim.com/topic/495968-vnav-disconnect-flying-the-coorz3-out-of-kden/

 

cheers!

-andy crosby

 

Great catch, thanks for this comment, that sounds reasonable.