Vertx Diamond DA-62 and holding altitude issue

[Ray Proudfoot 8,954]

Hi Jose,

After I posted that message I did a return flight from Milan back to Nice. I set an altitude constraint of my cruise altitude of 14,000ft and another of 5000ft between the mountains and the coast. Plenty of time to descend for a landing.

But at cruise and well before the calculated ToD the aircraft started to descend and this time it was more than a hundred feet or so. By the time it had descended 500ft I'd had enough and engaged a climb back up to 14,000ft. It stayed at that altitude until ToD when the descent started.

This is totally baffling to me. I know how VNAV works as I've flown the PMDG737 for a long time. If I was beta testing it I would class this as a bug. But you and others don't seem affected by this behaviour which makes me think I must be doing something wrong. But having watched the VNAV video from the people you recommended I'm doing exactly what I should be doing.

I'm going to fly Nice back to Milan tomorrow and this time I'll create just the one constraint at the FAF. If the aircraft descends I'll leave it alone and see where it ends up. I'll post the plan tomorrow which is a very simple one of around 4 waypoints.

One question. When VPTH is shown in white I know VNAV is armed. When the ToD is reached that should change to green and the descent should start without any input from me. I don't need to do anything else do I?

Thanks for your continued support.

[Ray Proudfoot 8,954]

Hi Jose, I flew LFMN VAMTU LIMC for a 35L landing. 4000ft altitude restriction at FAF. Cruise FL130.

I set a FPA for a 1500fpm descent. All was fine until 2m30s before ToD when the aircraft descended 200ft to 12,800ft and remained there until ToD. The descent was perfect. I wonder if it might be my settings in the DA62 Utility.

[jalbino59 114]

Hi Ray, Happy 2021!, I'm glad your're beginning to find your descents more manageable.  I don't know if there is anything within the utility that causes these altitude drops.  I cant check until I get back to my machine tomorrow. But if I see anything obvious I'll post a reply.  

Wishing you and yours a safe, prosperous and peaceful New Year,

 

[onebob 125]

2 hours ago, Ray Proudfoot said:

I set a FPA for a 1500fpm descent.

Hi Ray, been trying to do a test flight in P3D v5 hf1 since you first posted but having a lot of problems, (to long to try to describe them,) so decided this morning to have ago with ver 4.5, test flight from kmry to ksts. put additional waypoint at PYE and input the 32 approach ils for ksts.

Set 12000' altiutude and a restraint of 7000' at PYE.

Edited the current vnv profile FPA from 1.7 to a 3deg slope, at cruise alt (12000' alt) I  then entered 3000' alt for the coati waypoint. enabled Vpth ( in white ) then clicked on Vnav.

The TOD was now showing  on the flight plan ( wasn't getting that before) the vpth shown in white turn to active green after reaching the TOD and the airplane descended down to coati and passed pye at7000'.

I think the problem has been this value of FPA set at default of 1.7deg not allowing the calculation for the correct descent path and that's why i have not seen any TOD.

regards bob

  

[Ray Proudfoot 8,954]

2 hours ago, jalbino59 said:

Hi Ray, Happy 2021!, I'm glad your're beginning to find your descents more manageable.  I don't know if there is anything within the utility that causes these altitude drops.  I cant check until I get back to my machine tomorrow. But if I see anything obvious I'll post a reply.  

Wishing you and yours a safe, prosperous and peaceful New Year,

 

Hi Jose. A happy and healthy 2021 to you too. I tried a flight from Milan to Geneva, FL160 to clear the Alps and with a single constraint of 6000 for the FAF. That was absolutely fine. No early descent with a FPA to give a 1500fpm descent.

Another flight from Birmingham to Liverpool, England at 10,000ft and a single constraint of 2,000 for the FAF had the aircraft descending around 100ft well before the ToD. Otherwise it was fine. Odd, very odd why it doesn’t exhibit the problem on all flights. 

47 minutes ago, onebob said:

Hi Ray, been trying to do a test flight in P3D v5 hf1 since you first posted but having a lot of problems, (to long to try to describe them,) so decided this morning to have ago with ver 4.5, test flight from kmry to ksts. put additional waypoint at PYE and input the 32 approach ils for ksts.

Set 12000' altiutude and a restraint of 7000' at PYE.

Edited the current vnv profile FPA from 1.7 to a 3deg slope, at cruise alt (12000' alt) I  then entered 3000' alt for the coati waypoint. enabled Vpth ( in white ) then clicked on Vnav.

The TOD was now showing  on the flight plan ( wasn't getting that before) the vpth shown in white turn to active green after reaching the TOD and the airplane descended down to coati and passed pye at7000'.

I think the problem has been this value of FPA set at default of 1.7deg not allowing the calculation for the correct descent path and that's why i have not seen any TOD.

regards bob

  

Hi Bob. All that looks good. You didn’t get the aircraft starting a descent of 100ft or so before ToD?

Could you try LFMN to LIMC with a single waypoint as shown earlier and report back please. I think the problem is related to too shallow a FPA as you allude to. I’ll increase it to produce a descent rate of 1500fpm and try more flights.

[jalbino59 114]

On 1/1/2021 at 11:04 AM, Ray Proudfoot said:

Another flight from Birmingham to Liverpool, England at 10,000ft and a single constraint of 2,000 for the FAF had the aircraft descending around 100ft well before the ToD. Otherwise it was fine. Odd, very odd why it doesn’t exhibit the problem on all flights. 

Hello Ray,

So I just tried a flight. I climbed to cruise at FL090, once altitude captured and annunciated, I selected my approach and enabled VNAV on the MFD and as expected the G1000 automatically filled in my waypoint altitudes for the remaining part of the flight.  I adjusted FPA to -3 degrees and the G1000 calculated  comfortable approx -1000 FPM for my descent at my IAS of 150kts (180 kts GS). I engaged VNV on the AP and got the white VPTH annunciation.  So far so good. Then for some unknown reason after passing a couple of waypoints, I noticed the altitudes on my flight plan had changed from 9000 feet to 8900 feet.  My actual altitude did not change because I generally don't change the altitude window in the PFD until I'm about to start a descent. but if I had, the plane would have descended 100 feet to meet the next waypoint altitude.  Then after a couple of waypoints passed the remaining altitudes in the flight plan automatically changed back to the original 9000 feet.  I have a couple of questions for you and a theory... I know that the G1000 in the vertx does not allow you to select a STAR directly, but on your first flight (Milan/Geneva) did your flight plan import include the arrival procedure? did your second flight (Birmingham/Liverpool) have one.  The one I chose did not use a STAR.  It went direct to the IAF from cruise.  My theory... I'm wondering whether the G1000 in this vertx is coded to expect some kind of initial descent prior to the approach procedure and just reduces the altitude by 100 feet when it doesn't see one in the flight plan?  What do you think?         

Edited January 2, 2021 by jalbino59

[Ray Proudfoot 8,954]

Hi Jose,

To answer your questions first. Regarding the arrival to Geneva I don't select this in the DA62. I use Aivlasoft's Electronic Flight Bag and it allows you to choose the SID, STAR or Approach and when executed it's transferred into the default P3D plan and by definition into the G1000 plan.

All I did for Geneva was select the runway (04) and the ILS which creates a final waypoint as the FAF. I did this when at cruise of FL160. I don't touch the G1000 Arrival Procedures at all.

Same for Birmingham to Liverpool. Just a single waypoint after departure followed by selecting the arrival runway and ILS if available. The FAF is entered into the default plan and the G1000 plan.

On a flight today I didn't engage VNV at all on the G1000 right display. I don't know the exact description of it, sorry. Cruise was 10,000ft but even on a normal altitude hold flight it still descended a hundred feet or so. Personally, I feel this is a bug and if I was beta testing I would report it as such. The aircraft should not leave its cruise altitude unless commanded. I've never seen this behaviour before in any 3rd party aircraft.

Because I didn't engage VNV that side of the coding can be ignored I feel. The autopilot has a flaw which cannot be explained. Because once I initiate a climb back to cruise the same thing generally doesn't happen again.

I'm pleased you've seen this behaviour because I was thinking I was alone in seeing it. There doesn't seem to be any chance of discussing it with the author but I'm tagging @rogan who was kind enough to post some news from the author and he has produced some useful YT videos so may have an idea about this.

It's not a major problem and I can live with it. I just wanted to ask other users if they were seeing the same.

[onebob 125]

4 hours ago, Ray Proudfoot said:

I'm pleased you've seen this behaviour because I was thinking I was alone in seeing it

Hi Ray, managed to have a go at the flight LIMC/LFMN, used simbrief to generate the flight plan, had a few more waypoints in it but picked up ASBOP and BORD1,The flight waypoints ( in white )13000' filled in after clicking vnv, after that I noticed the flight levels had all change to 12900'.  edit... when i edited the first flight level they all changed back.

regards bob

Edited January 2, 2021 by onebob

[Ray Proudfoot 8,954]

@onebob, thanks for that. If they’re in white they’re advisory and will change if your altitude changes. The reason they’ve changed to 12,900 is because the aircraft has drifted down 100ft. Jose and I have both seen that happen.

Now that two of you are reporting the same issue I’m convinced it’s a bug which will remain unless the author responds. It’s something I can live with now that I know I’m not alone.