I have seen this problem a couple of times now. For my current flight, over 4300 nm, I have entered a FL of 300/340 in the FMC, set the altitude control to 30000 on the FCP, done all the profile and autoflight type things for take off. I take off and hit autoflight above 300' and the aircraft climbs as it should, all indicators are purple on the PFD, the speed, thrust, NAV2 and the preset altitude. The aircraft climbs to around 29500 and then switches to HOLD 30000 and won't climb any further - the engine mode also stays at CLB. The PERF screen on the FMC shows the optimal FL as being FL300 with a max of FL320. Any ideas what I have done wrong?

Can you post a few screenshots please?Paul

Can you post a few screenshots please?Paul

Flight has finished unfortunately, next time I'll try to grab some, if it happens again.

Were both altimeters reset to STD? I imagine that the AFS uses the on-side altimeter for altitude hold mode, so AP1 will use the Captain's data, and AP2 will use the FO's data. Don't ask me what happens if somebody selects the standby ADC though!Paul

Were both altimeters reset to STD? I imagine that the AFS uses the on-side altimeter for altitude hold mode, so AP1 will use the Captain's data, and AP2 will use the FO's data. Don't ask me what happens if somebody selects the standby ADC though!Paul

Yes both were set to STD - I'll try to recreate tomorrow.

Did your Opt/MaxFL in the MCDU show at or above your set FL. If the MCDU (FMS) (PERF pages) says that your max FL is 315 the aircraft will stop climbing at 315 and continue at that altitude. You may be able to climb 500 ft above the maxfl but not all the way to your set cruising alt, probably due to weight. as your flight progresses it should allow you to climb higher.

Did your Opt/MaxFL in the MCDU show at or above your set FL. If the MCDU (FMS) (PERF pages) says that your max FL is 315 the aircraft will stop climbing at 315 and continue at that altitude. You may be able to climb 500 ft above the maxfl but not all the way to your set cruising alt, probably due to weight. as your flight progresses it should allow you to climb higher.

The FL was set as 300/340 and the OPT/MAX was 300/315. Initially the Altitude was set to 30,000 on the FCP.

Ok, I'm in the air again and it seems to be behaving itself. The only thing that I can think of is that yesterday when setting the altimeters to STD I used a pre-programmed FSUIPC shortcut, this time I pulled the baroset knob