When making a FP from the world map or Simbrief, the FP’s have DISCONTINUITY in them. What is that and should I delete it?
Tonight in the CJ4-WT, I had a DISCONTINUITY right before the approach. This created a break in the FP and I had to fly via HEADING mode to the start of the approach.
Discontinuities are nothing more than a break in the flight plan. They are actually a good thing, and serve a useful purpose. They help separate a modified portion of the flight plan from an unmodified one. Or help separate different segments (such as an arrival and approach). So, if you want to load an approach that you are expecting to get, ahead of time, you can go ahead and load it and leave the discontinuity in place until you are actually given a clearance to fly that approach (or an assigned heading / vector to join). In sim world, you are typically safe deleting them as long as long as the route links up and matches what you want to fly.
OK, that makes sense. Thanks for that concise explanation sir.
Here’s a video explanation from one of the developers Mr. Matt Nischan. I fast-forwarded it to the point when he starts talking about it. Just click play below:
It’s unclear what’s supposed to happen if you don’t manually search for discontinuities and delete them. Am I expected to always search for and delete them every time an approach is added? If I don’t, will my plane fail to follow the flight plan?
Matt from WT here,
Yes, on the ProLine 21 (and most other FMCs), you are expected to review the loaded procedures and clear any discontinuities and/or patch up the sequencing as necessary. The FMS will command wings level when you reach a discontinuity, and will not sequence to the next leg, as a protection.
If the loaded procedure looks good, you may clear any discontinuities if you desire. It isn’t mandatory; many real life pilots will leave them in as a buffer and then go direct to the IAF once cleared for the approach. As in most things aviation, the pilot still has discretion on how they want to handle the specific scenario and there is no one correct answer for every case.
Most real life flights are much more active and use more AP modes than many sim flights. In real life it is exceptionally, exceptionally rare to be able to whack on LNAV and VNAV right after takeoff and then take that all the way to just before touchdown. So, don’t forget the “aviate” part of “aviate, navigate, communicate”.
-Matt
Thanks for everyone’s input on this. It has been very helpful.
Thanks! That helps clarify what’s going on. 
Very interesting. Just curious: what are the main causes for changing AP modes en route? Would it be level changes from ATC and avoiding weather?
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