Altitude variations in MCDU on STARs?

[pbrad74]

I did a flight today to LTFM with INBE2B arrival. I loaded my flight plan from simbrief into the MCDU through the ACARS option. At FM758 there is an altitude restriction of 9000, then the next flight restriction is at FM764 at 9000 also. The question is, why does the MCDU automatically assign higher altitudes in-between those two flight restrictions? Like 9700 ft then to 10200 ft? Is it normal to have to go through and change each waypoint in the MCDU?

[pbrad74]

So 9000, then to 9700, then to 10200, and finally back down to 9000 ft is normal on an approach? 

[Jeffrey Richard]

The only thing that I can assume is that the 9000 was an at or above altitude. If you see 9000 in bold font and the higher altitudes are in small font, then the aircraft is telling you the altitude that it plans on crossing those points on profile. If the 9000 was not a hard altitude ie. NOT an at or above, then it is a glitch to climb back up between points. I am assuming that the 9000 was actually an at or above, but the part that confuses me is the 9700 then the 10200, as those two would be reversed in the descent ie. 9000 was an at or above, then it would be 10,200, 9700, 9000 as the descent continued. Just an assumption.

 

[pbrad74]

Here is what I am talking about. You can see that FM758 is at 9000, not above or below and FM764 is at 9000 as well. The waypoints in-between in the MCDU are somewhere above 9000, can't remember. But similar to what I described in the post above. So my question is, is this simbrief's fault, something I'm doing wrong, or is it the A300 itself that is the problem?

[pbrad74]

Im thinking this must be an iniBuilds problem as I have not had this issue with other aircraft. I just loaded up another flight and still having problems where I have two waypoints with mandatory altitude restrictions with waypoints between those two points that have much higher altitudes assigned. This isn't making any sense. It's always happening with  STAR's. SID's and the rest of the route is as it should be.

[Crabby]

I have not seen this anywhere I have flown so far (US, Alaska, Canada, Mexico).  This actually sounds like a problem with the in sim nav data base or if you are using the Navigraph in sim replacement data, try it without because the A300 cannot read that.  I load up a flight to there just to see what is in the FMC for me. 

[Crabby]

I loaded up:

KRO2F KRO UN604 INBET INBE2B LTFM

From LGAV to LTFM

I don't see anything wrong with the SID and I am using Navigraph sim data.  Not sure what may be happening on your end.  

 

[pbrad74]

This is what I am getting. Compare to chart above. 

[pbrad74]

Okay, so then I'm clearly doing something wrong. I get the same thing as you until I complete the T/O, Approach, and Wind Desc pages.

 

[pbrad74]

Show me what you get after you fill out INIT B page. Because I get the same thing you do until I complete INIT B page, then I get what I just posted above.

 

[Crabby]

10 minutes ago, pbrad74 said:

Show me what you get after you fill out INIT B page. Because I get the same thing you do until I complete INIT B page, then I get what I just posted above.

 

Ok, after filing out INIT B I see the same as you.  Have you flown this?  If you have, does the aircraft follow those altitudes in Prof mode?  If you have not flow it, see if they change in the course of the flight.  

[pbrad74]

1 hour ago, Crabby said:

Have you flown this?  If you have, does the aircraft follow those altitudes in Prof mode?  If you have not flow it, see if they change in the course of the flight.  

Yes, I have flown it multiple times as it is a scheduled route for me and flying it right now. Indeed, in Prof mode, the aircraft will follow those altitudes. So I have to take it out of Prof mode. If I change the altitudes in the MCDU, sometimes it will follow and sometimes not. I don't know if this is an error with simbrief or an error with iniBuilds.

[pbrad74]

Yet another oddity. My TOD is after my first alt restriction. Keeps getting weirder and weirder.

[Crabby]

Really weird, I have not seen this behavior in other flights I have flown.  Not even the FMC gobbly gook spd/alt restrictions/predications or the T/D.  Are you using Navigraph in the sim as I am? 

[Crabby]

I don't think it's a simbrief error, in fact I am sure of it.  Everything looks fine until INIT B is filled out.  It is either some issue with the plane or some conflict with the navigation data.  

[pbrad74]

Gobbly gook, nice! Didn't think anyone used that term besides me and Matthew Colville. Yes, I am using Navigraph and the current AIRAC 2402 cycle. I haven't done a flight with the A300 stateside in quite some time though so I will try tomorrow and see how that works. It might just be messed up for that region? I don't know, just taking a guess at it.

[Deleted Account]

Could be either really haha

VNAV still isn't as good as we want it to be and we are still looking into refining it 🙂 

[dmb_nl]

I get the same (erroneous) behaviour for the LUNIP4L arrival in ENGM (Oslo). It has altitude constraints AT FL110 at GM416 and AT FL110 GM414, so VNAV should assign FL110 everywhere in between but it actually assigns higher values in between and ignores the first constraints. Funny enough, when I remove GM414 entirely, the altitude constraint at GM416 suddenly becomes active and seems to be considered by VNAV.

@Nico - GumbyI really enjoy the A300 a lot! I think VNAV is one of the very few points that could still be improved so I am happy you are working on it.

[Crabby]

On 2/25/2024 at 6:54 PM, pbrad74 said:

Gobbly gook, nice! Didn't think anyone used that term besides me and Matthew Colville. 

Yea, I am pretty old school in every way.

[sunnya]

I have seen the exact same issues on a number of flights since the release of the plane. The MCDU SID/STAR restrictions are shown correctly, but the next waypoint altitude would be very weird and not logical at all. Something must be wrong here, the A300 is the only plane I get this behavior. Cheers.

[pbrad74]

Quote

The MCDU SID/STAR restrictions are shown correctly, but the next waypoint altitude would be very weird and not logical at all

The most recent version fixed this problem for me. I've done at least a dozen flights since v1.0.9 was released and is performing much better. Do you have the latest version or did you buy from the MS Marketplace?