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Guest JaredA

MD-11 autopilot fighting to hold altuide

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I hope this hasn't been brought up before, but my MD-11s autopilot on the last few flights will climb up hold an altitude then step if needed then hold that for a bit then gets thrown off and it never recaptures the altitude it just climbs and descends in an attempt to recapture, but never fully captures it, any ideas? Sometimes I see it lose 2 or 3,000 feet in its attempt to recover with no success.

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I hope this hasn't been brought up before, but my MD-11s autopilot on the last few flights will climb up hold an altitude then step if needed then hold that for a bit then gets thrown off and it never recaptures the altitude it just climbs and descends in an attempt to recapture, but never fully captures it, any ideas? Sometimes I see it lose 2 or 3,000 feet in its attempt to recover with no success.
I have seen a similar problem in other acrft, not to that degree, but up to a 1000 feet in a slow but consist up and down. I thought it was due to upper level winds/turbulence but since installing a different WX engine program the problem for me has disappeared. I can only conclude that it may have been due to the former wx program I was using. Your problem may have a simple fix and may not be the same issue, but that maybe one thing to look at!Vincent

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Vincent, Yea, thats what I'm thinking as well I'm using Active Sky with a route loaded to not allow pressure changes, what do you use?

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Vincent, Yea, thats what I'm thinking as well I'm using Active Sky with a route loaded to not allow pressure changes, what do you use?
Jared...I wasn't going to give the name but yes that was the program and for fun I tested it last night. I started the flight w/ ASv6.5 and the problem began. I then paused the flight 2 hours into ,closed AS6.5 and started running ASA at that point and guess what, smooth flight rest of the way to Hawaii. Return trip tonight as well as every flight since using ASA no problems. You and I must have similar systems as I have not seen this talked about before. It was very agravating and I didn't know until installing ASA that it was may wx program. I thought it was something else but didn't know what ....VincentP.S. One good thing came from all this, I have a better wx engine in ASA but can still use ASv6.5 for the graphics in ASA w/out buying there new graphics program, and you can still use GE pro if you own that as well. If you can afford too, you may wish to consider this as a possible fix to the problem. VB

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Funny, been using AS 6.5 for a long time now, and have never experienced this behaviour in all my MD-11 trips so far... at altitudes up to FL390Strange...Andrew

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Alright, I agree Andrew strange indeed I know of others who use AS 6.5 with the MD-11 as well and like you don't see this fight for holding altitude and I might add that for me it doesn't do this all the time just every so often, I also noticed on the last flight SDF - EDDK that the autopilot would lose the altitude in this case FL330 then it would fight a bit then captured it then lost it for good. Andrew: How does your MD-11 behave if below FL390?

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Alright, I agree Andrew strange indeed I know of others who use AS 6.5 with the MD-11 as well and like you don't see this fight for holding altitude and I might add that for me it doesn't do this all the time just every so often, I also noticed on the last flight SDF - EDDK that the autopilot would lose the altitude in this case FL330 then it would fight a bit then captured it then lost it for good. Andrew: How does your MD-11 behave if below FL390?
Jared, Andrew, This behavior was not confined to just the MD-11. I don't know what wx conditions, routes or anything else would cause this to occur. I can only tell you that it has not reoccurred on my system and FS9 since using the new ASA program. Like many issues, not everyone will experience things reported. I can count on one hand w/ all the add-ons I have had since FS2000, and they are numerous, the problems which I have experienced being reported by others. This particular problem I was not able to pin down. I changed turbulence settings, winds aloft and several other things w/in FS and FSUIPC to no effect. It did not happen w/ every flight, but occurred more often then not. I was wrong recently w/ a problem which I thought was the MD-11 only to find out that since installing the new beta for ASA that problem as well went away. So, I am not convicting ASv6.5 but only offering a plausable cause and fix. I was happy with AS6.5 but will not use it again as my wx engine becuase of what I have learned recently, right or wrong. Respectfully, Vincent

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Jared,I wrote, "at altitudes up to FL390," implying that I have no issues at any altitudes up to and including FL390... I haven't taken the MD-11 any higher, as my ceiling has always restricted it...Vincent, I hope you don't think I was criticizing you... :) That was not my intention and I apologize if that is how my post came across...I was merely mentioning that, in all the years I have been using Active Sky, with any addons, that failures to hold altitude have always had another explanation. My immediate thoughts are max. ceiling... I had this once, failing to check what the max was, the aircraft (B737 I think) got near, but couldn't make it... kept on dropping, then trying to get back up... I realised my mistake finally and requested a lower level from ATC, with a severe portion of egg on my face... :DOf course, the permutations of options you can set for FS, AS, and so on, are so large in number, that no two systems will ever act the same, even with same settings I have come to believe...I am glad that you have found a solution, and thank you for sharing it with the rest... and once again, sorry if you thought I was criticizing that... believe me, I wasn't...Andrew

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Jared,I wrote, "at altitudes up to FL390," implying that I have no issues at any altitudes up to and including FL390... I haven't taken the MD-11 any higher, as my ceiling has always restricted it...Vincent, I hope you don't think I was criticizing you... :) That was not my intention and I apologize if that is how my post came across...I was merely mentioning that, in all the years I have been using Active Sky, with any addons, that failures to hold altitude have always had another explanation. My immediate thoughts are max. ceiling... I had this once, failing to check what the max was, the aircraft (B737 I think) got near, but couldn't make it... kept on dropping, then trying to get back up... I realised my mistake finally and requested a lower level from ATC, with a severe portion of egg on my face... :DOf course, the permutations of options you can set for FS, AS, and so on, are so large in number, that no two systems will ever act the same, even with same settings I have come to believe...I am glad that you have found a solution, and thank you for sharing it with the rest... and once again, sorry if you thought I was criticizing that... believe me, I wasn't...Andrew
NO NO not at all......sometimes things in writing like this come across wrong, looking at mine I probably seemed blunt. I never thought of altitude but I was getting this at all altitudes. In any event the problem has ceased....Again no apologize needed...Vincent

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