I have a couple of questions regarding the management of flight level (FL) by the Fenix A320.  Still learning the Airbus automation (my background is Boeing).

In a flight today, the imported Simbrief planned cruise was FL350.  When the A/C reached FL350, as expected the pitch mode changed from CLB to ALT CRZ.  Later I climbed to FL370 and pitch mode changed to ALT when the FL was reached...as expected.  Subsequently, I descended down to FL350 and I was expecting pitch mode to again be ALT CRZ but it stayed in ALT.  I PUSHED the ALT button but no change.  Shouldn't pitch mode be ALT CRZ again since the A/C is again on the planned vertical path ?  If "yes", how do I make this happen ?  If "no" why not ?

Second, sometime later in the flight I noticed that the FL was about to change.  FL370 in white font appeared in the flight plan and there was a new TC for FL370 and the FL for all downstream waypoints was FL370.  The Simbrief flight plan I had imported had no step climbs (FL350 was the only FL in "FL STEPS", no step climbs in the route).  The question is does the Fenix A320 automatically select a more efficient FL based on certain conditions, e.g., if the winds are more favorable at a different FL (when this occurred, had 103 MPH head winds at FL350) ?  If not what could possibly introduce this new CRZ FL ?

Thanks for your guidance

1 hour ago, zachlog said:

I descended down to FL350 and I was expecting pitch mode to again be ALT CRZ but it stayed in ALT.

If you want regain ALT CRZ mode, you have manually re-enter CRZ, in this case 350, in MCDU PROG PAGE via 1L key. ( In CLB this happens automatically when a higher ALT CRZ is selected).

2 hours ago, zachlog said:

does the Fenix A320 automatically select a more efficient FL based on certain conditions,

OPTIMUM FLIGHT LEVEL

The optimum flight level (OPT FL) indicates the most economic flight level for a given cost index, weight, weather data. It is continuously updated in flight. It requires a 5 min minimum cruise time, at a minimum cruise flight level of FL 100.

The OPT FL is a compromise between fuel and time saving. As a result, the flight crew may observe jumps in OPT FL due to GW, ISA, or wind changes. The computation of the OPT FL considers the wind entries made at the different altitudes (normally at the different CRZ FL). When flying the subsequent CRZ FL, the OPT FL proposed by the PROG page may be affected by the wind entries made at the previous CRZ FL; these winds are automatically propagated and may be significantly different from the actual winds.

9 hours ago, polosim said:

If you want regain ALT CRZ mode, you have manually re-enter CRZ, in this case 350, in MCDU PROG PAGE via 1L key. ( In CLB this happens automatically when a higher ALT CRZ is selected).

OPTIMUM FLIGHT LEVEL

The optimum flight level (OPT FL) indicates the most economic flight level for a given cost index, weight, weather data. It is continuously updated in flight. It requires a 5 min minimum cruise time, at a minimum cruise flight level of FL 100.

The OPT FL is a compromise between fuel and time saving. As a result, the flight crew may observe jumps in OPT FL due to GW, ISA, or wind changes. The computation of the OPT FL considers the wind entries made at the different altitudes (normally at the different CRZ FL). When flying the subsequent CRZ FL, the OPT FL proposed by the PROG page may be affected by the wind entries made at the previous CRZ FL; these winds are automatically propagated and may be significantly different from the actual winds.

Thank you very much for the responses to both of my questions but I do have a follow-up on the second one.

In general, is OPT FL a recommendation for the flight crew or is it added to the flight plan expecting the flight crew to follow it ?  I ask this because FL370 might have been in PROG/OPT FL telling the crew what's optimum (I had not checked) but it was also added to the F-PLN with a T/C entry (white font) and it was showing as the FL for downstream waypoints, i.e., the FL for each enroute waypoint was updated by the A/C automation.  This suggests that the flight crew is expected to follow it, decision made....maybe !!!  From the point of view of managing the F-PLN, what does the flight crew do to the F-PLN if:
                                                A- Agree with the OPT FL and go to FL370 as the new ALT CRZ
                                                B- Disagree with the OPT FL and want to stay at ALT CRZ FL350

9 minutes ago, zachlog said:

OPT FL a recommendation for the flight crew or is it added to the flight plan expecting the flight crew to follow it ?  I

OPT FL Is the level computed by the dispatch program used by the airline in which considering the PREDICTIONS of the various factors, regulations and restrictions, calculations are made to minimize flight time versus fuel consumption. However, in the end it is the decision of the Pilot in Command to take the best options taking into account the CURRENT conditions of the various factors that influence the airspace.

So we could summarize that the OPT FL would be the DESIRABLE to fly but not of a mandatory nature, because sometimes there will be external factors that prevent it (turbulence, level occupied by another nearby aircraft, air traffic management by the ATC). However, this will ultimately affect the calculated fuel consumption and flight time, with greater or lesser impact.

33 minutes ago, zachlog said:

Thank you very much for the responses to both of my questions but I do have a follow-up on the second one.

In general, is OPT FL a recommendation for the flight crew or is it added to the flight plan expecting the flight crew to follow it ?  I ask this because FL370 might have been in PROG/OPT FL telling the crew what's optimum (I had not checked) but it was also added to the F-PLN with a T/C entry (white font) and it was showing as the FL for downstream waypoints, i.e., the FL for each enroute waypoint was updated by the A/C automation.  This suggests that the flight crew is expected to follow it, decision made....maybe !!!  From the point of view of managing the F-PLN, what does the flight crew do to the F-PLN if:
                                                A- Agree with the OPT FL and go to FL370 as the new ALT CRZ
                                                B- Disagree with the OPT FL and want to stay at ALT CRZ FL350

@polosim I think he's talking about the OPT FL on the PROG page, and not the one given by dispatch.

As for an answer:
Recommendation. Usually there's a reason dispatch is giving you lower flight levels than what the FMS considers "optimum" (shorter flight, air space restrictions etc.), so it's quite rare that you decide just like that to go higher than planned. A more frequent reason to go higher (or lower) than planned is to gain distance from bad weather (turbulence, cloud layers etc.), since this can not be really planned for during dispatch.

3 minutes ago, Fiorentoni said:

think he's talking about the OPT FL on the PROG page, and not the one given by dispatch.

Thank you for letting me know, I think I misunderstood the question.

It should also be noted that the Airbus Software is notoriously conservative when calculating OPT FL. 

In real world operations the aircraft will often be flown higher.