747 Autopilot won't follow the FMC

[saltypete 0]

Hi all, i had this exact problem 2 weeks ago and i attributed it to running a trial version of Ultimate defrag. However it has happened again, this time i have not run the defrag or installed anything. In fact my computers settings are the same as when i solved this a fortnight ago. The flight is setup ( it does not matter where or how much fuel/load etc) When i take off i get to 500 feet and engage the autopilot and instead of following the flight director bars the aircraft pitches up to about 17 degrees then down again and then back up until i stall and crash. I don't know what the autopilot following its not the FMC as it's out of coordination with the Flight director. I solved this problem a few weeks ago by uninstalling the 747 the freighter add on and the sound patch then restoring the system to pre defrag and reinstalling the entire 747 package. I got 2 weeks of good flying and then today i get this problem again. I have restored my computer to the last day that i flew and it's still not responding. The only thing i can think of to do is to uninstall and reinstall everything again. I am desperate for any help i can get.I have had over 300 hours of trouble free flying and now this problem twice in 2 weeks......infuriating.RegardsPete Carlsen

[downscc 1,327]

Pete: Although once in awhile we need to reboot our computers, it is rarer still that an app needs to be reinstalled and I'm very sure that a problem caused by defragging is much rarer than that. Take it easy on yourself and start trying to figure out what the simulation is trying to do instead of blaming the computer or software.What happens if you don't engage AP until you are flaps up and accelerating to 250kias? If you don't have a problem there then work backwards... Another approach to this problem is to provide some information other than it is pitching up/down... weight and speeds, takeoff settings, etc... this kind of information will enable the forum to help you. The scenario you describe is not unusual, but a little more info is needed.Again, please save yourself the time and frustration of reloading software unless there is abosolutely no other alternative.Good luck.

[saltypete 0]

Hi Dan Thanks for the reply. I have tried what you suggested and tried reloading the flight at different weights. When i noticed the problem i was loaded to the gills for a flight across the Pacific. I tried again with a light load for a 400 mile trip and got the same behaviour. I also tried Flaps 20 and flaps 10 takeoffs with V2 speeds ranging from 137 to approx 170 knots ( dependant on fuel load) and still no dice. Finally i hand flew to 10 000 feet and tried engaging the autopilot and it still seemed to follow some other logic , besides what was in the FMC. As the plane was not following what the flight director was indicating it should do. Even by hand flying to cruise Altitude and then engaging the Autopilot the aircraft descended below the Alt set in the MCP and then climbed above the set altitude and repeated this process until all my airspeed bled off and a stall occurred.I know you said reinstall as a last resort, but i tried uninstalling the 747 package and tried reinstalling just the base Package. Again the aircraft exhibited the same behaviour described above. Really running short of ideas i then uninstalled all my add ons and FS9 also and did a complete reinstall. ( i was meaning to do this at some point as i have a new harddrive added to my system). It took me 4 hours but after extensive tests all seems to be fine. I tried test flights after installing the base package, then the freighter add on and the aircraft performed perfectly. I am happy that the 747 seems to be working properly but am none the wiser to what caused the fault in the first place. I apologise if i was too verbose in this reply but i wanted to make sure that i included as much information on the characteristics of the problem as possible.Regards Pete Carlsen

[downscc 1,327]

Does your simulation work in SPD or LVL CHG modes with HDG mode (in other words, try it without VNAV/LNAV)?

[saltypete 0]

Hi Dan, exactly what i was thinking about doing should this problem resurface. I have read that V Nav can cause problems both in the sim and real world. Captain Mike Rays' simulator checkride manual mentions that V Nav can cause behaviour that is strange and seems to work on a logic all of its own. I am hoping that this won't happen again however as i did a complete reinstall of FS9 and all my addons. A hassle i know , but i have been meaning to put FS on a separate harddrive for ages and finally i had the perfect excuse to do so. A blessing in disguise perhaps? Thanks again for your patience and advice Dan, and have a very merry Christmas and all the best for the New Year.Kind regardsPete Carlsen