VNAV advisory

[TrevorS 28]

Hi Hans

 

I posted this problem way back in September 2017 and was told that it was on your to do list after the LNAV issues were corrected.

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This still appears to not be working properly. I did a flight from EBBR to EDDM in the -700.

The distance from TOD appeared on the MFD (in VNAV mode) 49nm from TOD. The time to TOD was also displayed.

Then at 27nm to go, the distance got "stuck" at 27 nm ( no longer decreased) to go but the time continued to count down to 1 minute.

 

There also seems to be no correlation between the snowflake on the ADI and the blue doughnut on the VSI.

Surely the snowflake should appear at the top (like a GS indicator) and as you get closer to the TOD, it should move down to the centre when you reach TOD. At this point, the blue doughnut should start moving

on the VSI to indicate rate of descent required. I believe the original Wilco CRJ worked like that. Makes sense.

 

I also found the snowflake to be very "jumpy" at times. It also disappears and then reappears during DES as does the blue doughnut.

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Just did a flight from EDDB to LOWW and the problem is still there.

Is this problem ever going to be resolved?

 

 

Regards

Trevor

[TrevorS 28]

Some feedback / assistance please Hans

 

Trevor

[TrevorS 28]

your sarcasm is totally unnecessary!

[Hans Hartmann 3694]

@TrevorS, his sarcasm is necessary and very much to the point! This forum is not my life. You will have to accept the fact that I occasionally do pointless things like work, sleep or watch a movie.

 

Now to your question: Advisory VNAV has received a major rework months ago and was tested for quite some time during a lot a flights. By myself and by the people who volunteered for testing. Advisory VNAV (snowflake as well as blue ball) are only displayed while you're in a 3 degree corridor around the optimal descent path. And like with the glideslope of an ILS, the closer you get to the end of the descent path segment, the smaller this 3 degree corridor becomes. That's what you describe as twitchy. Back in 2017, the corridor was calculated waypoint by waypoint, now it's calculated constraint by constraint. It's much more precise and much less twitchy than before.

I can't comment on the T/D distance issue as I've never seen that problem. I usually just look at the green dot on the MFD and that moves totally fine without getting stuck.