Still getting this irritating FMC message, please help...

[Guest kelvind80]

Hi there,I feel something's seriously up with my 747-400 for FS9. It has the most recent update, service update 1.2 (22nd May 08) and it said it has corrected the UNABLE NEXT ALT Logic, but mine doesn't appear to have.I've attatched three pictures to show you my point. Basically I'm on RW27R at LHR; on a WOBUN 2F, no additional weather changes, just the basic weather. I am using full TO and CLB thrust. She's weighing 384,200 KG so a little heavy, I have a ZFW of 235,900 KG, and the distance is ~4,800 NM.Firstly, have I calculated the fuel right with an alternate as KOAK, then Sacremento as a second - 75NM = 3,600 KG; and also holding time about 40 mins = 6,100 KG, and minimum landing fuel of 10,900 KG; which ultimately equals 17,500 as the reserves (MLF + ALT + 1/2 HLD = 10,900 + 3,600 + 3,050), so a planned landing weight of 260,000 - which is well within the limits, so just wondered if I was over calculating somewhere.Which leads me onto my second problem: if you look at my pictures (in order) you'll see the trouble I'm having. The first one before VNAV is armed, you can see that it states there's an error that I'll be 760ft below the constraint. Second picture shows that I've armed VNAV and received the UNABLE NEXT ALT message because of the error. Then I've shown that (as all ways when I fly that, just to test it to see if any change) I'm way above the constraint, let alone the error of -760. I have the screen shot at 3,000ft, which is ~3 NM from Burnham which is where the constraint is set... and when I continued the flight, I was infact at 4,000ft so way above what was required.So please, please help me rid of this error. I'd be most greatful.Thanks a lot,Kelvin D

[downscc 1,327]

This exact same departure has been used to describe the UNABLE NEXT ALT message at least twice in the past month. I suggest that you do a search to find the detailed discussion. In summary, the message may be considered an advisory that is based on a profile inside the black box.Another famous SID in this context is LOOP at KLAX. A heavy Queen might have to work at it to get over the constraint at the LAX VOR since most of the flight path is in a turn.Bottom line, the message is an advisory not an error. Good piloting techniques, such as you demonstrated, will be able to exceed the AT OR ABOVE constraint. I like the AT OR BELOW 6000; when light, you can almost feel the neg G's as you push the nose down to stay low.

[Airbrakes 0]

To get rid of the Advisory, simply press the CLR or clear button on the bottom right corner of the FMC.... Once you pass that waypoint you shouldint get that message again.