Help understanding VNAV page in PMDG 747 F

[Krister 51]

This is something I haven't come across before and need some help understandiing! I am currently enroute EDDF-KBOS and let FSBuild create a flightplan that is accordingly loaded. I am at FL320 (Max is FL328 and recommended FL280 according to the FMC). I have been flying for about an hour so I still have a looong way to go.For the first 30 min everything looked normal and I had the CRZ page up on the VNAV page on the FMC. I left the simulator for 15 minutes and when I returned it had gone to the DES page. If I manually go to the CRZ page the only thing I see is L1 CRZ ALT waiting for an entry (boxed), OPT and MAX. There is nothing else there - no STEP TO, KBOS ETA/FUEL or ECON SPEED. If I enter FL320 into L1 it goes to the DES page, however I see the complete CRZ page momentarily before it changes.Obviously I should have the CRZ page open since I have 8 hours left. What have I done really?!Update: Initially I loaded the airplane with the fuel amount FSBuild suggested and added a few tons. The FMC complained about not sufficient fuel which is nothing unnormal. But I now tried loading almost double the amount of fuel and I still get the not sufficient fuel message although I am established in cruise.And as a further update: I tried descending to FL280 as the FMC wanted as optimal. I was in VNAV/LNAV mode and enter FL CH however the aircraft speeded up from 315 to 400 during the descent. Shouldn't it have maintained 315? Now I am totally lost!

[Krister 51]

I think I should look up how I actually loaded up the aircraft. Fuel flow is 4 on each engine and all engines are at 103% just to maintain mach 0,80 at FL280! :)

[cowpatz 243]

Was the gear up? :D CheersSteve

[Krister 51]

lol.. I actually checked for that! :) But yes, and I still have no clue to what actually happened. It goes into the archive with the other x-files!

[Tabs 2,790]

You don't want to be flying near Max Alt like that - you want to be at or slightly below the Optimum Alt on the VNAV page... Then step climb as you burn off fuel...

[Krister 51]

And that is also what I usually do, this was just an exeption. But what can explain the fact that I got the DES page so early in the flight? I've never seen it before and the "only" thing I did different from earlier crossings over the atlantic was that I fiddled around with the load manager for the 747-400F (for the first time) and set it to 2/3 full (if I remember correctly - not full anyway). As long as it doesn't show its ugly face again, it really doesn't matter, but IF it does I wonder what I should look for! :)

[opherben 0]

a. For economical cruise, you want to cruise initially the round thousand figure at or above OPT ALT available for your direction of flight, in your case FL280. Then use step climb, set 2000 in FMC vice ICAO for RVSM airspace, and follow the PROG page data.b. Set engine rating to CON, to ensure sufficient excess thrust to overcome atmospheric changes.c. To deal with the FMC irregularity, set the AP to maintain current flight path, reload your route, place the next route fix in LSK1L on Legs Page1, then VNAV and LNAV. When set correctly and installation undamaged, it will fly properly.>You don't want to be flying near Max Alt like that - you want>to be at or slightly below the Optimum Alt on the VNAV page...> Then step climb as you burn off fuel...