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Guest SkullxBones

747 MCP CMD buttons modeled correctly ?

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Guest SkullxBones

I always see the real world pilots use the center CMD button on the MCP. I read that the reason for this was that selecting either the right or left button would turn off the F/D on the side you selected and only the center button allows the F/D for both pilot and co-pilot at the same time so that's why it's always selected.But my FSX version of the PMDG747 shows the F/D on both PFD's no matter which button I select. Has the real world MCP been updated since I read that or is the PMDG modeled incorrectly?Jeff P.

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Guest jumbojock

Try to think of the autopilots and FDs as different things. You or the autopilot are doing the flying and being commanded visually - the flight directors - by what's been selected on the MCP. The FDs are turned on and off by the FD switches on either side of the MCP, not by autopilot use.There is an exception to this, however, when pressing the TOGA switch on the go-around, but I'm not sure if it's modelled. I only have -400, not the X version.jj

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Guest SkullxBones

>The FDs are turned on and off by the FD switches on>either side of the MCP, not by autopilot use.That might not be correct, that's why I am posting the question.According to what I have read and seen, the autopilot does affect whether you can turn on the F/D. With the FSX version of the 747 (I don't know if the FS9 is the same) you can turn on the F/D with the F/D switches and they will work no matter which CMD button is selected.But the question is, does it work the way in real life?According to captain Mike Ray a 747 type rated pilot, you NEVER select the right or left CMD button, always the center CMD button when you turn on the autopilot. And in all the real life 747 videos I have seen it always the center CMD button that is selected.The reason is that if you select the right CMD button, the pilot can't turn on the his F/D. Likewise if the left CMD button is selected, the co-pilot won't be able to see his F/D. Only the center CMD button will allow both the pilot and co-pilot to see there F/D at the same time.So the question I have is if this is still true or have they changed the way the CMD buttons work so that you can turn on the F/D's not matter which button you select?

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I certainly am not a 747-rated pilot but based on the real-life 747 documentation (960+ page manual) the CMD/FD buttons are modeled correctly in the PMDG's 747. The CMD buttons seem to be completely decoupled from the FDs - this follows from the textual description as well from the provided schematic of 747's AFDS (Autopilot Flight Director System). There are some 747-rated people around who will know for sure ...(if I were a 747 pilot and given a choice I would definitely prefer such clear 'decoupling').Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg


Michael J.

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This feature is an option for the 747-400. I dont know of many airlines that has chosen this feature, but United is one of them. Capt Mike Ray flew for United so he is very familiar with this option. Uniteds 757s and 767s also have the same feature. There are 3 flight control computers. With this option enabled, each fcc can provide flight director commands or autopilot commands, but not both. So with the captains fd switch on, the command bars will be in view on the captains pfd if the left autopilot command switch is not engaged. And likewise for the right autopilot and the first officers pfd. If the captains and first officers fd switches are on and the center autopilot is engaged, then both pilots will have the fd command bars on their pfd's. During autoland, both pilots fd command bars will be removed from view at 1500ft when all three autopilots engage. A. Cole

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I vaguely remember reading somewhere that this is a pin-point programming thing. Airlines can choose if they want their FD to stay ON when that particular FCC (Flight control computer) is in control or not.The advantage of selecting the center AP is that you can check your three FCCs during flight. The aircraft is being flown by the Center AP which uses the Center FCC, the captain looks at his FD which uses the left FCC and the F/O looks at his FD which normally uses the right FCC.One interesting note for aircraft where the FD disappears when the FCC on the same side is in control:During an autoland, ALL your FD's will disappear when you get the LAND 3 annunciation on the FMA as all three FCC will be in control.Regards,SylvainEDIT: I see A. Cole types faster than me ;-)


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