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simpilot22

FMC Help

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Would someone direct me to a resource to better explain the functioning of the FMC? I've printed and read all available with the PMDG. I created a flight from KALB to KISP, and entered all appropriate data into the FMC, including all waypoints. Once airborn and directed by ATC to resume own navigation, I entered LNAV and VNAV on the MCP. The AC did not seem to follow the DIRECT TO Athos as entered. Regardless, I received vectors to follow, and switched to HDG and entered the courses.I completed the flight without difficulty, but other than managing the V speeds and climb thrust, I'm not quite sure of what value the FMC was, at least on this particular flight.Any guidance at all, for this rookie, would be greatly appreciated.ThanksChip B.

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The most likely reason for LNAV was that you did not have a current heading to intercept the LNAV path for it to capture. Next time try it be within 3 NM of the LNAV path and on a current hdg that will cross this path, it will actually ARM then engage. Try it next time.[h4]Randy J. Smith[/h4]


Randy J Smith

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Thanks Randy,Does it sound to you like I've at least gotten the right idea? When vectored by ATC away from the flightplan, is it simply switching from LNAV to HDG? If I am directed to assume own navigation, is it a matter of enabling LNAV again, or must I first assume a heading towards the FMC flightplan? As you can see, I'm trying to wrap my head around this... not so easy for a rookie!Thanks!Chip B.

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Yes you must be pointed in the direction or a direction that your current hdg will CROSS the path on the ND and within 3 NM. So resume OR take the next WPT on the legs page and place it into the 1st LSK and EXECUte for a DIR TO..[h4]Randy J. Smith[/h4]


Randy J Smith

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Guest boxjockey99

From experience it is much easier to bring the next waypoint to the top which is what Randy quite rightly suggests. We quite often get put on headings by Manchester radar on departure, these headings more often than not take us away from our flightplanned track. When ATC tell you to 'go direct to...' or 'own nav' they are expecting you to go DIRECT to the point in question NOT try to re-intercept your previous track, after all they just vectored you off it for a reason! So SOP for most 737 operators is to bring the desired waypoint to the top this is done by:find the waypoint in the legs page (may need to use NEXT PAGE)Use the LSK on the left next to the waypoint to bring it into the scratchpad at the bottomIf on any other page than page 1 of LEGS the hit the LEGS button to get back to page 1Once on page 1 of LEGS press LSK Left1 to place the scratchpad data in line 1 and effectively bring the waypoint to the topNow make sure the line it draws looks sensible (ie in the right direction) then hit EXEC. Once EXECuted remeber to hit LNAV on the MCPNote if the cleared point is not in the legs page then you can just type it into the scatch pad then put it at the top but this may end up with the wrong waypoint so checking it looks sensible is VERY important! eg direct SAM (Southampton - UK) can end up direct direct SAM (Samos - Greece!) which is quite embarrasing!I agree with randy that you need to be within 3nm but I think the other requirement is within 90degrees of a closing track so unless the heading is way off the track (not normally the case) LNAV should go in without too many problemsThe FMC is VERY useflu and once you have grasped the LNAV function and start learning the VNAV functions then you will appreciate the magic box far far more primarily because it removes the need to do all that mental gymnastics needed for descent planning and makes a continuous descent profile a real consistent possibility.Hope that helps, if you need anything else explained just askHappy trailsKris

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Thanks Gentlemen!I appreciate the input. The FMC is a very intimidating tool for a rookie. I have yet to find a tutorial that explains what you have just described. Just what I needed!I am attempting to use the 737NG with VoxATC and FS2Crew. It's alot to grasp, but at least I'm getting the AC up and down in a controlled fashion.Again, I appreciate your help. As I go along, I am certain I'll have further questions.Blue SkiesChip

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