Why the slow climb to cruise altitude in 747x?

[Guest horizonflyer]

The past couple of flights I have taken I have noticed that when I am about 5 or 6 thousand feet from my cruise altitude (usually anywhere from 330-360), using autopilot with VANV/LNAV engaged, the 747x all of a sudden for no reason drops to a really slow climb and almost stops climbing completely. I notice no other issues with the aircraft when this happens, any thoughts?Thanks,Tom

[FLEX1978 373]

Information like gross weight, Air tempreture wind speed and direction, climbing in FLCH or VNAV etc would help a lot.Rob

[Guest horizonflyer]

Rob:I load the 747x 2/3 full of fuel with the fuel planner, can't think of gross weight at the moment off the top of my head, wind speed is not anything out of the ordinary when it usually starts the slow climb around FL270 or 290. And I am always in VNAV.And I have only been in the Atlas Air repaint 747X freighter.I can take a screenshot and attach it next time it happens.Hope that helps.Thanks,Tom

[lehbird 48]

I took my first flight with this AC yesturday (ironically, the same model and livery you reverenced Tom!!) and had similar problems. I could not get a climb rate of more than 300FPM above 29,000. Granted, I was ~80% full of cargo and fuel. I could be wrong, I just thought a 747 could climb a little better than that at that altitiude, with that configuration.

[Guest horizonflyer]

>I took my first flight with this AC yesturday (ironically,>the same model and livery you reverenced Tom!!) and had>similar problems. I could not get a climb rate of more than>300FPM above 29,000. Granted, I was ~80% full of cargo and>fuel. >>I could be wrong, I just thought a 747 could climb a little>better than that at that altitiude, with that configuration.lehbird:Glad to see that I am not the only one affected, hopefully we can find out why. Tonight I am going to try a smaller fuel/cargo load and see what happens.I'll keep you posted.Tom

[posherid 2]

Hi,it looks to me that the issue you have is that your trying to climb with your cruising speed (most likely above mach .84 and at that speed don't expect miracles. Try to limit your speed to .82 and you'll quickly see the climb rate increasing (in VNAV mode). However at that level, a climb rate around 1000 fpm is not at all abnormal (if you're fully loaded). Typically also the initial flight level will be around FL290 - FL310 and you'll only be able to climb higher after having consumed some fuel (it can take easily 2 hours before you're able to step climb to the next level).