A310 doesn't follow descent profile (ignored bug?)

Thanks, I’ll do a test with CI 40 and this option in order to see if I can land on LIRP :smiley:

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Oh, just for fun. As long as you are not constrained by a speed constraint on the STAR (or by ATC), some guys will prefer to go to selected (manual) speed and dial it up, rather than select speedbrakes, if they are getting high.

You’d be surprised (and not always in a good way😉) at the kind of rate of descent you can get by dialing the speed up from say, 290 to 320.

There’s a bit of robbing Peter to pay Paul there. You are going to need to lose that speed at some point. But, within reason, the extra parasite drag from the increased airspeed seems to mitigate that at least a bit.

The last part that we didn’t even talk about is wind. A big tailwind can make an easy descent hard in general and, if they have changed since you input them, can definitely put a kink in your FMS’s descent calculations.

Honestly, I’ve read some conflicting info on when and where the FMS does it’s descent profile. But, if you asked me how often the Bus updates its profile in the box, I’d say, “Less often than you’d think and less often than it needs to.”:wink:

So, figuring where the 310 keeps its winds and making sure they make sense, will probably solve some problems for you.

I will say that most guys don’t and just deal with it since winds shift, the box isn’t perfect, and the more time you spend nit noiding the box, the more lilely it is that ATC is going to vector you off or shout a speed change at you.

But, in MSFS, some of that at least won’t be a problem for you! :+1:t2:

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A little OT. During FMC programming, for flight plan, the iniBuilds guy say that we can follow this flow:

  1. SID
  2. STAR
  3. All waypoints/airways in the middle
  4. Clear one of the double points on the route (the one before discontunuity)
  5. Clear discontinuity

Is the point 4 of the list correct?

I guess it depends on the context.

If programed properly, the FMC should usually take out obvious double waypoints. It will also often connect (and so close) discontinuities as long as the sequence is clear.

So, the Zuni transition to the SEAVU arrival to the ILS 25R at LAX, no discons.

The SWL transition to the JIIMS arrival to the ILS 27R at PHL, discon between STAR and approach.

You should generally be careful about closing discons unless you specifically filed to the FAF. Otherwise, it’s probably not what you were cleared for.

Same thing on departure. Vector SIDs may not connect you to the first point, and you are not cleared there. So you should leave it open.

If they are speaking of discons you create as you manually enter the Flight Plan, those are fine as long as it ends up reading the same as your clearance, not skipping anything and not adding anything extra.

Also, be mindful that some double waypoints are in there for a reason. Specifically, there are usually two or more waypoints near any procedure turn or holding pattern on the approach. If you delete the wrong one, the aircraft may try to do something it shouldn’t when it gets there, like blow off the procedure turn and make some kind of whifferdill to get itself back around to the Final Approach Fix.

Did any of that answer your question? :joy:

For example try with the route on the opening post:



WAYPOINTS/AIRWAYS (in the middle):

You will end up with this:

Is it correct to remove only the discontinuity or have we to remove the first NORNI after (T/D)?

LOL, well that was a rabbit hole. Get ready!

So, loaded up the 310 for the first time. Got here. Noticed that the NORNI1R doesn’t have a transition. Wondered if that could make anything different.

Got the same result as you.

So, as suggested, I deleted the Discon, deleted the NORNI before the Discon and it all linked up. I did notice that the label denoting M729 was also deleted. But in this case M729 runs one point between ELB and NORNI with no other waypoints along the airway. So, nothing was deleted of importance. Perhaps, if there had been other points on M729, it might (should) have kept them.

So, the instructions you have do work.

Out of curiosity, I tried something more familiar, I tried the HLYWD1 arrival, GABBL transition into KLAX rwy 25L. This arrival chain is one that should link all the way through the runway.

Well, for one thing, the MSFS 310 FMS doesn’t allow you to land 25L from this arrival, which I do routinely sooooo… :wink:

So, 24L then.

Same result. This time without a double waypoint because I routed to TNP which isn’t also on the arrival.

I was pretty sure that isn’t how it works on the 320, so I tried the same thing.

The first thing I discovered is that the MSFS 320 box is a hot mess! :rofl:

I did manage to figure it out though and loaded the HLYWD to the ILS25L.

The 320 box closes the discon automatically.

I didn’t really trust the MSFS 320, so I tried this same thing on the Flight Factor A320 in X-plane. I use this to study for training, so I think it’s pretty realistic.

Here’s the arrival page into LIRP.

And, as you can see, the discon is automatically closed.

So, short story endless, in the MSFS 310 at least, the FMS requires you to close some discons that newer boxes do automatically. I don’t know if this is realistic, but from watching guys in the A300 sim on occasion, that’s not at all impossible.

Now, does any of THAT help! :rofl: :rofl: :rofl:

Ah, sorry for the convoluted answers. If I had been home to try the sim myself, I probably could have answered them more directly. As it was, I was off on a trip and was just throwing spaghetti at the wall and seeing what would stick! :crazy_face:

Many thanks for your reply, a very detailed answer.

What we’ve learned here is that sometimes is not so simple to verify if there is a simulation bug or not, each airplane is different and we don’t have an A310 pilot in order to ask to him!

A very glad conversation with many useful concepts.

Maybe I can tick as solution the answer from @CD0139 .

As I wrote before, in order to know if there is a bug in the FMC we need an A310 pilot, maybe you can reach one :smiley:

P.S.: maybe it is more reliable to leave all waypoints in the route except for the one that is exactly the same (on my route the point before discontinuity has the tag M729 and is not the same as the one after)

Sadly, I don’t work with 310 guys anymore. There just aren’t that many around.

But your right to say that the way these boxes work, it can be tough to say that one is working as it should.

Even the 320 box in MSFS may work better than I think because it’s modeled after a different software load or option.

As to leaving the point in, I would surmise that it doesn’t matter in this case. As long as all the points on M729 remain in the flight plan, if you take it out the double point it should still go to the correct location.

And if you don’t take out the extra point, it should just cycle through them.

The place that you need to be careful is where multiple points are part of a procedure.

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