Unable Cruise Altitude

[greg100o 12]

I am new to 747 400. I successfully completed the Illustrated Guide to Getting Started with the PMDG 747 tutorial, where everything worked flawlessly.I then tried to set up flight from Seattle to Portland Oregon, cruising at 15,000, similar weights etc. But in fact no matter what altitude I put in for cruise even 8,000 it says Unable Cruise Altitude, and one cannot finish programming the FMC and get on with the flight. No way do I beleive that the 747 cannot reach 15,000 feet in a 150 mile flight!Anyone with an idea of what I am doing incorrectly? I do not see this error specifically in the manual.Thanks,Greg

[Tabs 2,790]

Are you setting the reserve fuel option in the FMC to something really high? That can trigger it if so...

[greg100o 12]

Ryan,It was actually set at zero.Greg

[crvm 0]

You are most likely heavy and the TOC point on the path is overlapping the E/D point while in ECON VNAV. It's not that the aircraft cannot climb - it's that you have to think about descending all while the AFDS is in control. You can lower your needed fuel - Do not use a reduced thrust takeoff - Modify your crz altitude - Select MAX ANGLE spd through the FMC's CLB page. Weight is most likely the main factor here...Best,Randy J. Smith<<>>

[Guest aputzich]

Hi Greg,I had the same problem and found out that this goes away when you specify a departure runway (at least that worked for me).Andreas

[Guest Peter Lloyd]

GregHit this same one myself last weekend on a KBFI-KPDX trip. (Nice convenient familiarization trip on the 74). Southbound departure onto the St Helens SID doesn't have enough airspace to get up to 15000ft on a derated climb and back nice and easy to PDX. You can get up there OK, but you sure have to get down in a rush to get to the right height overhead Battleground. Try a northerly SID departure from KSEA or KBFI.(Guys in Seattle are fussy about noise reduction.)I don't like the northern approach for 28L or R at PDX, so favor an easterly approach from the Dalles. Have a play with setting up some fixes off KPDX to get a nice smooth transition. This is a really good route to practise these on. Spokane is another good short trip from Seattle.EnjoyPeter

[greg100o 12]

THanks folks I will give some of these tips a try as I progress along!Great airplane!!Greg

[greg100o 12]

After spending a lot of time looking at different scenarios, I find that not filling is a value in the FMC for fuel reserves caused the "Unable Cruise Altitude". Why this is so makes no sense to me. There is mention in the manual that if nothing is filled in it is assumed to be 4,000 pounds. I wonder if this is a bug.Greg