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Drew_Melia

..."turn heading nnn until suitable ? for navigation is received"

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There I was ploughing along my filed flight plan when suddenly RC4 asks me to more-or-less U-turn with some garbled message about a suitable navigation something or other. Its happened to me a few times now... I can't figure out what it means... after about half an hour I get fed up and turn back onto my flight plan, but within minutes the controller is turning me around again. Why does this happen and what can I do about it? This is RC4.3 for FSX, and at the time I was flying a PMDG 738 NGX

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Sounds like u missed a crossing restriction?

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You may have missed as stated a crossing restriction (be sure your altimeter pressure is set to standard or local pressure as needed depending if you are above or equal to the local transition altitude) or you missed a waypoint credit. If the latter check the status area of the RC flight window to see if that waypoint that you think you crossed popped off.If RC commands you to change to a flight level then your altimeter needs to be at standard pressure (29.92 in or 1013 mb) and if RC gives you an altitude in feet in will give local pressure to set to.In the first case you also may have been vectored to an airport with a limited approach.Remember if you get a vector that is from your present position direct to the next commanded waypoint. You do not return to your original path in your nav equipment.

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Ah... right.... come to think of it... I didn't miss a constraint in terms of height/alt, but I did notice that the "next waypoint" as indicated in the RC window was NOT the one I was actually flying to.... which begs a question... often an FMC waypoint is not overflown... most FMC's can cope with that and treat it as a "past" waypoint.... but can RC? and what about mandatory holds and intercept points?Thanks Chaps... appreciate it

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Ah... right.... come to think of it... I didn't miss a constraint in terms of height/alt, but I did notice that the "next waypoint" as indicated in the RC window was NOT the one I was actually flying to.... which begs a question... often an FMC waypoint is not overflown... most FMC's can cope with that and treat it as a "past" waypoint.... but can RC? and what about mandatory holds and intercept points?Thanks Chaps... appreciate it
Depends on how close you come to the passed waypoint - the limit appears to be about 2 miles. RC knows nothing about mandatory holds. What do you mean by "intercept points"?DJ

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The waypoint tolerance depends on your AGL altitude and phase of flight.From page 90 of the RC manual:"IMPORTANT NOTE – DP checkpoint tolerance is 2 miles. You must fly to within 2 miles of a filed checkpoint for credit. You must receive credit for all filed checkpoints. Checkpoint tolerance outside 30 miles of your departure airport (enroute) is 5 miles."If you miss a checkpoint you can skip by requesting a direct-to selecting the extended RC menu page (default 9), selecting direct-to, and then selecting the checkpoint from the list. Again, that is direct from your present position to the commanded waypoint. That avoids the reverse vector to the missed waypoint. To affect a direct-to in a Smiths (Boeing 737/747 type) FMC you do a direct to by on the LEGS page LSK the next waypoint of choice (which can include the first on the list) which will place it in the scratch pad. Then LSK the top (first) waypoint again (even if it is the same one) and activate and EXE the change. I do this while in HDG mode and switch back to HNAV after the list is refreshed with the new heading.In the B737 there is a bank limitation you have set with fifteen degrees preferred for passenger comfort. The aircraft will start turning prior to the waypoint so the turn is bound by the current path to the waypoint and the path from the waypoint so it does not overshoot. The lower the bank limit and the faster you go, the earlier the turn starts. This is called predictive steering. You can choose to go slower until after that large course change or take MCP HDG control to overshoot a bit allowing the aircraft's track to be closer to the waypoint and on then on the FMC "double punch" the next waypoint if you are close to the original path before you return to HNAV or just steer back to the original path and engage HNAV. The default heading tolerance on the RC options tab is 15 degrees. I keep it at 25 degrees to take care of any discrepancies due to long legs and great circle navigation differences.If you are using the NOTAMS flexibility option in RC you also have heading tolerance but the checkpoint proximity to get checkpoint credit not your crossing restriction altitude remains the same to pop the stack.

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I guess the moral of the tale is "read the manual" lol. I had no idea RC had built in waypoint tolerances. I'll be more careful next time! thanks guys!Oh, and I'll erm.... read the manual!

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