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dogs53

FMC Loading, messages, and discos

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Hi all...I need help from some of the Pros on this forum.I am having 4 strange problems that pop up occasionally when flying the PMDG737-700.For example on a recent flight from KOKC to KORD, I looked up the actual flight plan from SIM Routes, and then loaded it into the FMC... I think that the route was "J98 TUL EOS J181 BAYLI BDF5" I didn't select an arrival RW, figuring that I'd do it enroute. Prob. 1. The FMC wouldn't let me put J98 into the plan prior to TUL, so I just put Direct TUL, Not a big deal.Prob. 2. When I selected an arrival RW (I think that I selected RW 14L) about 100 miles out, I got a disco that I couldn't resolve in the normal manner. I tried to click on the valid option below the disco, and then click on the disco, and it wouldn't clear the disco. Could this be because the RW wasn't compatable with the STAR that I selected?Prob. 3. On this same flight, the flight plan path took me directly over KORD, and then tried to do a sharp 90 degree turn to the west, and then a sharp 180 turn to the east to line up on the rw that I selected. THe plane couldn't turn that quickly. Again, could this be because the STAR and the RW don't work together, or is this something else?Prob. 4. I often get the message "DES PATH UNACHIEVABLE" or something very similar to that on the FMC. Why does this happen? Shouldn't the FMC compute this in advance and begin descending at the correct TOD point?I am sure that I am missing something simple, but would appreciate any advice on this and what I can do to prevent it.ThanksBob LeBoeuf

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Well for starters youre missing the first waypoint for J98. You need a VOR or an Intersection to join the airway.When you select a new runway ( 14L in this case ) go to the Legs page of the FMC. The runway should be on one of the last pages. If the runway has a specified approach ( ILS, VOR, NDB etc ) then press the approipate LSK for the IAF.... Usually the first waypoint pass the discontinuity. That will place the IAF in the scratchpad of the FMC. Then press the LSK above the discontinuity to clear it. Activate then execute.As far as the "DES PATH UNACHIEVABLE" I think thats related to the discontinuity.

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THanks for the info.. Good point on the VOR before J98. I thought that I did as you suggested on the disco, but I'll try it again.Thanks for your helpBob LeBoeuf

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Youre welcome..Just remember to always activate and execute or the changes woulnt be saved or linked. If the problem presists, could you post a screenshot of the FMC's legs page?

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KOKC J98 TUL EOS J181 BAYLI BDF5 KORD: The FMC needs a fix on the airway to join the airway (and most real computerized flight plan interfaces such as DUATS require this too).None of the STARS at KORD (and most places in the US) connect to an arrival. The STAR serves to take you as far as approach control who then will vector you for the arrival (even RNAV STARS work like this). There are a few locations where an IAF for an approach is also included in the arrival, but certainly not KORD.There are custom SIDSTARS that connect the arrival to approach, in fact I have been providing these for 68 US locations for several years in the AVSIM library. I'm missing this cycle (0810) due to hardware problems, but when I get back into service I hope you give them a try.

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Dan...Thanks for your answer, but I am not understanding something (definately due to my inexperience here)... So let me try to ask the question in a different way. I am trying to understand about why the turning directions were so severe... 90 degrees west, and then 180 degrees east... I would have thought that it would have pulled me from the STAR and then moved me to the west to avoid such sharp turns and to allow for a softer intercept to final. I might be wrong here, but in this case, I think that the last fix was ORD. If so, then should I have deleted that fix from the FMC before I added the RW so that the plane wouldn't try to fly directly over the airport, and then turn? And, if so what is the best way to do that?Thanks again for your help and for your patience with "Rookies" like me.Bob

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