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flightsimmer747

"not on heading intercept" apearing through flight 737

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I'm banking at 30 degrees in case and it just won't activate LNAV I keep getting this annoying error, why does it keep coming up everytime I click LNAV. My route is fine the pink line on the flight plan is there, so why doesn't it intercept?

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What's your intercept angle? Should work if it's in a reasonable range, 30-45 deg normal. Too much difference between you and the desired track and you get the "not on intercept heading" msg.I fly hdg mode until I'm lined up with desired track within a couple of degrees then engage LNAV.. lots smoother, sometimes it will increase the intercept angle if you're off course as if its in a hurry to get on the track.


Dan Downs KCRP

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While Dan's explanation is true if you turn your aircraft with heading to the interecept limit and engage LNAV my experience is that it will try to join the existing flightpath displayed on the ND which may not be the correct goal for the current nav environment.If in the case of ATC commands or your own wishes to go from present position to the waypoint at the top of the LEGS page 1, LSK it to get it in the scratchpad and then LSK it again. This will update the path from your present position to that next waypoint at which point you would turn the aircraft near the intercept heading and engage LNAV as Dan states.I use this all the time when Radar Contact is vectoring me and then gives me a resume navigation command which expects direct to the next waypoint it has determined.Also be prepared to proceed direct to a waypoint further down the LEGS page by LSKing that point and then LSKing it over the next waypoint (top page 1 LEGS) to create a new path for LNAV. This might occur as you are using HDG to follow vectoring or the prescribed path but were not close enough to the waypoint to have the LEGS page give credit (pop the list) and you need to go to the next.Each change needs an EXE to activate.This is just a practical application expanding on Dan's reply.


Ron Ginsberg
KMSP Minnesota, Land of 10,000 Puddles
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Hi guys,I'm not in this flight anymore but I beleive from what I recall I may have missed a waypoint due to my flight plan having an SID and I didn't fly it, since I'm following fs9 ATC instructions. Sounds like this may have been the problem. What do you think?At that point the LNAV did not see what it had to intercept a few waypoints later, now your saying I can update my FMC to fly from where I am sort of like a proceed direct to function? When I kept selecting my next waypoint from legs menu it kept asssuming this was my route discontinued from that waypoint on. What may i be doing wrong? I reread your post I'm sort of understanding it, but can you clarify the difference between, LSK twice to update path from present POS to next waypoint vs LSK anywhere else in LEGS menu to proceed direct to ANY waypoint, and as to why I may be getting my route diconnect error?i think my main problem is all related here, unfortunately I hand flew the flight man what an experience! :)Hope I'm making sense!

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You may have to delete a few old waypoints between your "new" waypoint and the old one on the legs page so they are in order. If you have the DISCO error that stands for discontinuity in the LEGS sequence so just see what is going on and eliminate the discontinuity.Think of the procedure as a copy/paste, not a cut/copy. So the old stuff remains and may open up a discontinuity (DISCO). I do not have it in my head and I'm not right now where I can do it.I just went through the same type of departure routine and had to delete a waypoint which opened up a DISCO. If with the exception of the DISCO boxes everything is in order just LSK the waypoint beyond the DISCO boxes after CLEARing the error message in the scratchpad, then LSK to boxes to close it, then EXE. It is hard for me to detail this while not experiencing it.The procedure is in the FMC tutorial.If you can spare $35 or so for the book and its handling, I highly suggest getting retired captain Mike Ray's hard copy spiral bound Flying the BOEING 700 Series Flight Simulators PC Edition available from his web site at www.utem.com where you can look at sample pages. It is also at several sim shops (including here) and amazon. It covers the most practical FMC operations in a tutorial form as well as advanced operations, interpreting instrument charts, aircraft nav operations, etc. It has three tutorial levels and is an entertaining read as well with lots of practical flying material thrown in such as go/nogo icing decisions.The PMDG documentation is concise but complex. This tutorial guides you very well.The book perhaps limited in context is available in .pdf format for some other Boeing product owner and is included with those purchases.His suggestions on when to use LNAV and VNAV and when to use MCP control and/or hand fly are based on real world experience and are well worth reading.


Ron Ginsberg
KMSP Minnesota, Land of 10,000 Puddles
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Ron:I appreciate your expanding on my short notes. You usually give me a different viewpoint than what I was focused on. Thanks.By the way, last time I was near MSP I met a bunch of guys who love the winter for the ice fishing... really an odd thing for a guy from So Texas to hear someone say. Also heard that your state is land of 10,000 lakes, 10,000,000,000 mosquitoes and a couple of fish. I guess you've probably heard that one tho-


Dan Downs KCRP

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The mosquito is the state bird :) .


Ron Ginsberg
KMSP Minnesota, Land of 10,000 Puddles
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Just got a chance to read the message I'll be trying out the exact same flight plan and try your tips and see if my problem was really having skipped over a waypoint due to ATC vectors.Thanks

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LNAV engagement criteria in flight:- Active route entered in FMC- Within 3 NM of active route, LNAV engagement occurs with any airplane heading- OUTSIDE 3 NM, AIRPLANE MUST BE ON INTERCEPT COURSE OF 90 DEGREES OR LESS AND MUST INTERCEPT THE ACTIVE ROUTE SEGMENT BEFORE ACTIVE WAYPOINT.Good Luck,Floyd


John Floyd

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I think thats the difference "before ACTIVE WAYPOINT, I may have passed it and 30 miles later tried getting on course (pink line). My heading was right so I was still heading towards destination airport.

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