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I know it is impossible to climb with a fully loaded aircraft to FL390. How do I calculate the target altitude with the combination of aircraft weight. If I let the FMC do the work, the aircraft immdediately wants to climb to FL330 or more. Is there a manual or something else.

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The Vnav page on FMC will tell you what the optimal altitude will be in the beginning of your trip and then will show you the first step-up.Michael J.


Michael J.

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Yes, but sometimes the engines have to work very hard to bring the aircraft to the altitude in the FMC. Sometimes the speed reaches the stall speed. That's why I thought there is another way to calculate the climb.

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Guest ilh

I have never beeen anywhere near stalling when climbing with VNAV or FLCH to the FMC-calculated optimal altitude. Climbing with V/S and too high a setting could lead to a stall as its first priority is vertical speed, not airspeed.Are you using POSKY's aircraft.cfg or .air file?Lee Hetherington (KBOS)763 PIC/POSKYv3 Merge

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Guest

I'm using the Wilco air file and the POSKY cfg. file. Should this cause the problem. I experiencend these problems when , for example, climbing from FL290 to FL330, about 20 minutes after take off with filled tanks. The engines were unable to lift the aircraft to this altitude. The result was that the speed dropped below 180 kts. or less.

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Took off last night fully loaded, over 400,000 lbs gross. The FMC gave me optimal altitude FL280. By the time I was at FL220 the new optimal altitude was shown to be FL290 so I made it climb to FL290. I was never close to any stall. I noticed that when you later want to do the step-up climb the power stays in the CRZ mode - FMC wil not switch to the CLB mode automatically for some reason. It is OK but it makes for a slow climb (again, far from any stall). You can engage a CLB mode on the thrust panel manually and then the climb is brisk.Michael J.


Michael J.

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Read my note at the top of the forum. This explains what to do with the aircraft.cfg file.

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Guest Martin

>It is OK but it makes for a slow climbSo? :-) Step climbing is not like going to the moon. You just want to get there, and you don't want to make the passengers too aware of it. CRZ should be enough...Oh, and another word for step climb is cruise climb (I believe that's what's used in the ATC terminology in the US?) so it would be logical to have the plane in "cruise" mode.MartinIt's a lot like life and that's what's appealing

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Guest

Yes, again I had the problem. I was climbing in LNAV/VNAV and step climb 1000 so the FMC showed the most comfortable and economical climb. But as the aircraft continued to climb to FL 290 and higher, speed was decreasing to a very dangerous value and I had to stop the climb. The fuel load was about 90.000 lbs. I'm using the Posky airfile. What am I doing wrong? Is it possible to climb within about 150 miles to FL300 or more???

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>I'm using the Posky airfile. What am I >doing wrong? You answered it yourself - you are using Posky airfile, this is wrong.Michael J.


Michael J.

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Guest

What's likely to be wrong is that you are using the POKSY air file.Try using the PIC aircraft with a PIC airfile, or - better yet - use Lee Heatherington's PICPOSv3 merge....you can find it easily in this forum if you look.Rob.

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