A320 FMGS B44

[Fritz]

Hello,

On my last 4 ILS approaches I have observed that the speed by managed speed is not sufficiently reduced.
I have activated approach in the MCDU and pushed the APPR Switch on the FCU.
A target speed of about 175 kts is displayed on the PFD. AP1 and AP2 is activated.
The speed is reducing to about 200 kts and I set the flaps to Flaps1 but for Flaps2 I am to fast.
The autothrust accelerates again. When I set the Speed to manuall on the FCU,
a Speed of 204 kts is displayed on the FCU. I adjust the Speed to 145 kts, then the autothrust does not
accelerate again and I am able to set flaps up to Flaps4.
Without manual intervention, the auto thrust is not automatically reduce the speed enough.

This problem I have not had before. Can anyone confirm this?

I use the FCU from CPFlight.

[romeow]

Hello Fritz,
I've observed more or less the same issue (using still version 39). I've noticed as well that wind speed changes worsen the behaviour of ATHR. Make a test with no weather and probably you will see that ATHR works perfectly.

A kind of workaround: If ever there is windy weather don't use managed speed until you are on the GS.
Regards
René

[Fritz]

I use FMGS version 44.2. Have upgraded from Prepar3D 2.5 to Prepar3D 3.1 during the holidays.
I've had this in different weather situations. Once at 1 kts crosswind or 4 kts headwind
according to METAR, same behavior. I'll be watching it on.

Thanks for your reply.

Regards Fritz

[jeehell]

At some weights, the managed speed while in flaps 1 (green S speed displayed on PFD scale about 1.24*stall speed in clean configuration) is at or very near the VFE of flaps 2 (fixed 200kts). This is a known issue on the real A320, the PERF of the aircraft sometimes require selected speed input. Also, in descent, the aircraft will always be hard to decelerate to extend the flaps. Sometimes you NEED to lower the gear (particularly in some ILS with slopes of 4°).

JL

[romeow]

Hi Jeejell,
your description ist exactly what I experience from time to time but it's only a part of the "problem". An example what I (and probably Fritz) mean: descent, current speed 250, speed set 210 (managed or selected doesn' matter), VS -1400. N1 should be reduced now to idle (the blue indicator arcs of N1 show this input requirement!) but ATHR stays more o less constantly on a power input which is too high so that the aircraft is accelerating in addition to VS . Even increasing VS (e.g. -2000) to force ATHR to cut the power setting doesn't help. ATHR stays unimpressed at a certain N1%. You have to disable ATHR to force the engines to idle.

This behaviour is not reproduceable. As I said before I assume there must be a context with the weather engine(s). On flights with no weather (no ASN and FSUIPC weather settings off) I haven't been confronted with this kind of problem so far.

Regards
René

[jeehell]

Varying winds do cause this kind of problem, even on the real ATHR...
I really suggest you limit FS/P3D to light or moderate turbulence at maximum. More than that will really cause issues (the turbulence is much too strong in FS).

JL

[iperne]

Hi JL!

First of all, thanks for your great job. I am old PM and AST user, but I must tell, that your FMGS is more profesional then others.
With last update B44.2 works everything fine, except elevator trim not reset to zero, when AC touch down.
And one question. How to reset Appr phase - back to normal flight speed. In real A320 just input new FL on PERF page and that deactivate appr phase (speed go up to CRZ)?

Best regards
iperne

[jeehell]

Hi,

Thanks for the kind words!

With last update B44.2 works everything fine, except elevator trim not reset to zero, when AC touch down.
And one question. How to reset Appr phase - back to normal flight speed. In real A320 just input new FL on PERF page and that deactivate appr phase (speed go up to CRZ)?

I will try to solve the elevator trim reset soon.
Regarding the APPR PHASE reset to CRZ, I thought this was already implemented, maybe it's not yet released or it is still buggy, I will check that.

Best regards,
JL

[romeow]

Hi Jeehell,
thank you for your explanations! Be sure that I'm very happy with your software and I'm aware that we all move in a simulated and not real world. There is no problem for me to live with a certain imperfection and compromise! As far as I know that it's not me or my setup which are imperfect everything is fine!

My deep respect for your work!

Best regards
René

[OmniAtlas]

Hi JL -- any plans to implement 'FIX INFO' (lateral revision at waypoint) into the MCDU so we can fix radials into the MCDU? Thanks.