1 minute ago, Bobsk8 said:

I have never seen that in about 30 flights. Are you flying the Fenix? 

Of course I fly the Fenix. What else is there to fly? 😜 Give it a try yourself: while descending (!!!) in managed mode and QNH set and active, move it up a lot (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point upwards and the V/S needle go down (higher V/S). Set QNH lower (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point downwards and the V/S needle go up (lower V/S). As I said, no big deal (and I presume realistic) but when the difference between the old and new QNH is huge this might become unpleasant and hence I'd like to prevent this from happening. But also with smaller changes I can see the plane react.

But well, anyway, since no one seems to be able to answer my simple question LOL (I expected one or two clear answers, not a discussion filled with confusion LOL) I think the best idea is to pre-set QNH during cruise: this way it will probably and usually still be the same later on, when I have to go from STD to QNH or the difference will be 1 or 2 at the most. And that's not a problem. 😉

2 minutes ago, tup61 said:

Of course I fly the Fenix. What else is there to fly? 😜 Give it a try yourself: while descending (!!!) in managed mode and QNH set and active, move it up a lot (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point upwards and the V/S needle go down (higher V/S). Set QNH lower (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point downwards and the V/S needle go up (lower V/S). As I said, no big deal (and I presume realistic) but when the difference between the old and new QNH is huge this might become unpleasant and hence I'd like to prevent this from happening. But also with smaller changes I can see the plane react.

But well, anyway, since no one seems to be able to answer my simple question LOL (I expected one or two clear answers, not a discussion filled with confusion LOL) I think the best idea is to pre-set QNH during cruise: this way it will probably and usually still be the same later on, when I have to go from STD to QNH or the difference will be 1 or 2 at the most. And that's not a problem. 😉

I just descended into KPHL about 20 minutes ago, and was playing around the altimeter settings, and saw no difference in the VS or speed.  

Edited June 12, 20223 yr by Bobsk8

2 minutes ago, G550flyer said:

I do get that in other countries, you may be closer to the ground and destination when this change over happens.

Where I live that's 3000 ft instead of the US standard of 18000 ft! 😉

2 minutes ago, G550flyer said:

The displayed altitude may rise or fall a little and the plane will slightly pitch accordingly.

Exactly. And just in case I know the difference between the two numbers is huge I'd like to preset it.

But well, anyway, I only started this topic because I remembered reading a trick to pre-set QNH during descent and because I can't find that post anymore I decided to ask it. It's no dealbreaker LOL I regret bringing it up now LOL

2 minutes ago, Bobsk8 said:

I just descended into KPHL about 20 minutes ago, and was playing around the altimeter settings, and saw no difference in the VS or speed.  

Well, then something is wrong with YOUR setup LOL 😉 Just kidding, Ignore this entire topic please. Lets move on to more important topics.

4 minutes ago, tup61 said:

Well, then something is wrong with YOUR setup LOL 😉 Just kidding, Ignore this entire topic please. Lets move on to more important topics.

I am starting another flight now, I will try moving the altimeter setting further and see if I see what you are seeing. 

I just wanted to clear up that you would see the AP response to altimeter settings when level and making changes. You wouldn't see it make a difference in climb or descents unless it was in ALT capture mode and you changed it. Wanted to make sure that was clear.

1 hour ago, tup61 said:

I know I know I know! 😉 I see a reaction only when I change QNH while descending. And I want to prevent that by pre-setting the correct QNH before I have to switch to it. 

I‘ve as well seen the Fenix doing this. In principle I think it is correct behavior although I think it updates the vertical profile a bit fast and harsh.

When you change the baro setting during descend in managed („DES“ on the FMA) it means the vertical profile of the FMGC is used. Obviously it is a difference where you are in the descend profile depending on the baro setting. So when you change this, you can also observe that the green dot beside the altimeter band on the PFD changes (indication for vertical profile).

So again I think the Fenix behavior is correct, but I guess the real plane smooths the change in vertical profile and does not react that prompt as the Fenix does it.

The way I do it:

During climb, before setting altimeter to STD I change to the forecasted QNH at destination.

During descent, when cleared to an altitude below transition level, I change to local pressure. If I have to change the pre-set value it doesn’t alter the descent profile. 

Edited June 12, 20223 yr by Cpt_Piett

I am on descent, I just changed the altimeter about 5 turns of the knob, the vertical rate never budged.

From the FCOM it sounds like it works the same as in a Boeing, not sure if the Fenix has this modeled though. 

When the flight crew pulls the barometric reference knob, the barometric reference is set to STD.
When in STD, the flight crew can turn the barometric reference knob to preset a QNH value.
When the barometric reference is set to STD, and the flight crew pushes the barometric reference
knob, the barometric reference changes to QNH or QFE (depending on the last barometric
reference in use before switching to STD).
When the barometric reference is set to QNH (QFE), and the flight crew pushes again the
barometric reference knob, the barometric reference changes to QFE (QNH).
 

27 minutes ago, BrianW said:

When in STD, the flight crew can turn the barometric reference knob to preset a QNH value.

LOL If it could be that easy...! I will give this a try during my next flight! 😁

EDIT
Gave it a try and yes, you can indeed change the preset QNH while the windows shows STD! Only it doesn't show you what you set it to... so you have to remember the old setting and count the clicks you turn the knob precisely... But perhaps you CAN preview the number somewhere else? On one of the displays maybe?

Edited June 12, 20223 yr by tup61

Wow 3 pages,

As I am descending I use the ATSU to get WX, 

I have all 3 baros set independently

Once I get the Baro I set it on the standby,

Then at some point that suits I press the Captain baro top press, set the baro to match the standby and then bottom press it again to set back to std

Then I repeat on the FO side, then all I do is come out of std when needed and there all set perfectly.

/sigh…….

2 hours ago, tup61 said:

 while descending (!!!) in managed mode and QNH set and active, move it up a lot (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point upwards and the V/S needle go down (higher V/S). Set QNH lower (like 20 ticks) and you will see the yellow arrow on the speed tape starting to point downwards and the V/S needle go up (lower V/S). As I said, no big deal (and I presume realistic) but when the difference between the old and new QNH is huge this might become unpleasant and hence I'd like to prevent this from happening. But also with smaller changes I can see the plane react.

If you want adjust the QNH during a climb or descent and not have it affect the AP+FD vertical guidance, why not just select VS mode briefly whilst your fiddle with the setting knob, then switch back to whatever vertical mode you were in after?

Can't speak for an Airbus, but on a Boeing if you just turn the QNH set knob while in STD, the setting that you're selecting appears in small white font below the active QNH (which will say STD) in this scenario.  At transition, pressing the STD button will toggle your armed value to active. 

Now, to make VNAV take the altimeter setting change into account when calculating descent path, you enter the destination QNH in the descent forecast page of the FMC.

The PMDG 737 models all of this correctly. 

All you need to know about STD in Fenix:

 When altimeter setting are blinking you need  press "arrow up" on altimeter knob and then "B" on keyboard!