CRJ vnav and vs modes

[RF pilot 35]

Today I flew the CRJ 700 and had the vnav option enabled.  Just before the TOD I set the altitude and pressed vnav.  The plane immediately dived and I had to disengage vnav, stablise the altitude and wait for a bit before rengaging vnav and it seemed to work pretty well up until LOC was captured and approach pressed.  As soon as approach was pressed the plane dived again and I just about managed to avoid crashing but obviously had to go around.  Please advise if I am doing anything wrong or if this is a bug which will be fixed.  If it will be fixed do you have an idea when?  By the way I have now flown this plane (and the 550) four times since release, and I absolutely love it!  It is a real pleasure to fly and want to congratulate the team on doing such a good job, it really is a fantastic aircraft and very immersive.  Well done!

[Secondator 643]

Did you have FMA indication VPATH and did the aircraft try to follow the snowflake at all or did the aircraft just dive compeletely out of the profile?

About the ILS please check this:
 

 

[RF pilot 35]

Yes the vpath and snowflake were showing but the aircraft ignored those and just dived completely out of the profile.  I wonder whether this is because I pressed the vnav just before the TOD?  Should I have waited until after TOD passed by?

 

On the issue with the ILS problem I had, could this also be related to the vnav issue?  Should I press the vnav button once it reaches the approach altitude to ensure it does not interfere with the ILS glideslope?

[Secondator 643]

1 hour ago, Rudy Fattal said:

Yes the vpath and snowflake were showing but the aircraft ignored those and just dived completely out of the profile.  I wonder whether this is because I pressed the vnav just before the TOD?  Should I have waited until after TOD passed by?

I was able to now recreate it on my test flight. I'll have a further look into this and document it on our issue tracker. Thanks for the report. It could be related to the ILS issue. I am not sure currently and will have this investigated.

[moxiejeff 10]

I had a similar issue with one of my flights as the OP did.

[Chaxterium 119]

8 hours ago, Rudy Fattal said:

Yes the vpath and snowflake were showing but the aircraft ignored those and just dived completely out of the profile.  I wonder whether this is because I pressed the vnav just before the TOD?  Should I have waited until after TOD passed by?

 

On the issue with the ILS problem I had, could this also be related to the vnav issue?  Should I press the vnav button once it reaches the approach altitude to ensure it does not interfere with the ILS glideslope?

 

 

I've had similar issues but just let me add that you should be able to press the VNAV button at any point before the top of descent. It's somewhat similar to arming the APPR mode. Once you're given a clearance to descend at your discretion you can arm VNAV and as long as you have a lower altitude in the altitude select window then it should start the descent on its own. I've noticed that it tends to start the descent a couple miles after the TOD point but from that point on it seems to do quite well.

 

That said, as I mentioned I have noticed the issue you're describing. Both with VNAV and ILSs.

[V1_Rotate 2]

Is there an update to this? The airplane still dives when I engage VNAV prior to the TOD. It should maintain altitude until I intercept TOD. So I engage VNAV just prior to TOD and the snowflake is below when in the real plane it would be above prior to the TOD. I think that is why the plane is diving prior to the TOD. Also, when VNAV is engaged, you should get FMS speed (cyan speed bug) and I don't see an option for that. Any ideas? 

[Raptor05121 84]

On 7/9/2022 at 7:29 PM, V1_Rotate said:

 Also, when VNAV is engaged, you should get FMS speed (cyan speed bug) and I don't see an option for that. Any ideas? 

I've been wanting this as well. Not modeled