More 320 autopilot issues

  • I was on a flight from Seattle to Fresno, and everything seemed fine as the plane climbed to FL350. However, once we reached FL350 the autopilot immediately went into DES mode and began very rapidly descending. The vertical speed was approaching -4000fps and it hadn't stopped increasing the descent rate when I logged off. This is the opposite of the time it continued climbing when it reached the chosen FL, but probably a symptom of the same problem. The autopilot was still set to 35000, and no inputs of any kind had been made to the autopilot.

    I have flown several flights where the altitude capture and indeed the entire autopilot performed flawlessly, but this failure to stay at the selected altitude has now happened twice in five flights for me.

  • Hi Oldar,

    yeah that's a bug that comes from the boeing part of the autopilot. If you set the correct cruise altitude it just goes into DES mode but doesn't actually descent right away. What you can do is selecting a lower altitude than the cruise altitude and then climb using OP CLB (pulling the altitude knob once in the air).

    You get the correct flight plan cruise altitude when you have the flight plan loaded, then exit the sim, come back and then place the aircraft onto the departure runway.

    Both, the necessity of closing of the sim and the activating DES mode instead of ALT CRZ is a bug that I already fixed internally. I'm at IPACS' headquaters today and chances are good that these bug fixes make it to the public soon.

    Apart from these already reported bugs, are there any bugs that you collected? Maybe start a new thread and collect all of them. The more eyes the more bugs can be found and resolved :)

  • Well, sometimes when I am turning onto final the autothrottle goes into TOGA mode. I know others have seen this too. The only solution is to turn off the autothrottle. As already mentioned sometimes the plane is set up correctly to start a flight, and sometimes it is not. And I still sometimes get screwy top of descent pips of 240 to 320 miles from the destination. That is a long way away for the plane to start descending.

  • Today I made some changes to the fly by wire that make it less likely go activate A.FLOOR and TOGA LK. it will no longer pitch up to maintain the protection angle of attack (stick neutral). It will only start pitching up to alpha max if you hold back the stick now.

    You can disable toga lock quite easily, just move the levers a bit and you are back in speed mode.

    Is that early descent still a thing? huh... Are you sure? Can you give me an example route please where this happens?

  • I had a slight problem last night when flying on AF2. I was landing an A320 with an automatic landing at Zurich. All was going well and I was established on the localiser and glide slope, speed 140 knots, with full flaps, auto thrust on and no speed brake. In the landing phase, just before rolling out, AP deactivated and I had to land manually instead.

    Please advise on the above - perhaps my landing speed was too low, however, all was working very smoothly until the final point.

  • This happens when the airport glide slope is not 3.0 degrees. 2.5 and 3.5 degrees should work most of the times but then the calculation of the altitude offset get's messed up. Below 120 ft the glide slope needles really start to move quickly, below that altitude I ignore large glide slope deflections.

    Above 120ft large glide slope deflections will cause the autopilot to revert to basic vertical modes (V/S or FPA in the A320) and if you fly with those below 50ft RA the AP disengages.

  • This happens when the airport glide slope is not 3.0 degrees. 2.5 and 3.5 degrees should work most of the times but then the calculation of the altitude offset get's messed up. Below 120 ft the glide slope needles really start to move quickly, below that altitude I ignore large glide slope deflections.

    Above 120ft large glide slope deflections will cause the autopilot to revert to basic vertical modes (V/S or FPA in the A320) and if you fly with those below 50ft RA the AP disengages.

    Thanks and understood, however, how can I avoid this as the glide slope and AP are controlling my descent?

  • Couple of questions more than issues:

    1. It seems to take a little while to switch from HDG to NAV - I can reach the selected heading, click the HDG switch before the turn, which adds NAV in blue to the main screen underneath HDG, however, it can take a couple of minutes to then switch back into NAV mode. Any ideas on why this is the case?

    2. Occasionally, I will hear a clicking sound and the system will change from NAV to HDG. Again, any idea what causes this?

    Thanks

  • 1. You have to intercept the flight plan to resume NAV (as in the real world)

    2. Because you lost NAV is falls back to HDG (as in the real world). That means the autopilot lost the ability to follow the flight plan and that you should pay attention to what it is doing now. That attention getter is the triple click. You get the same clicking sound if you are flying an ILS approach with LOC and G/S and disable the loc function. Then it reverts back to heading mode but the vertical mode also changes which may not have been intentional. Again, to raise attention a triple click is sound.

    The cause of NAV loss is a high lateral deviation from the flight plan. 2.5 NM is the maximum lateral deviation allowed which can occur if you are flying manually or try to intercept the flight plan and overshoot it.

  • 1. You have to intercept the flight plan to resume NAV (as in the real world)

    2. Because you lost NAV is falls back to HDG (as in the real world). That means the autopilot lost the ability to follow the flight plan and that you should pay attention to what it is doing now. That attention getter is the triple click. You get the same clicking sound if you are flying an ILS approach with LOC and G/S and disable the loc function. Then it reverts back to heading mode but the vertical mode also changes which may not have been intentional. Again, to raise attention a triple click is sound.

    The cause of NAV loss is a high lateral deviation from the flight plan. 2.5 NM is the maximum lateral deviation allowed which can occur if you are flying manually or try to intercept the flight plan and overshoot it.

    Thank you!

  • Another question if you don't mind.

    Occasionally when clicking the APPR button to activate an ILS landing, it instead gives me APP NAV and FINAL instead of Glide Scope and Localiser (auto thrust and AP activated, as well as following NAV).

    Any idea why this happens?

    I can have a normal flight and do all of the same things to the same airport (say Geneva or Zurich), where occasionally the above happens and doesn't result in an automatic landing.

    Thanks in advance.

  • Hi, as in the real world this happens when there is no ILS approach selected.

    In Aerofly I currently have no information about the approach itself, as the autopilot I just see: do I receive a signal strength? yes then let's fly the ILS.

    In your case you pressed the button too early. Just wait for the ILS to be received, then press the button. However the autopilot should revert from APP NAV and FINAL to ILS if it becomes available.

    The rest is pretty realistic:

    If no ILS has been programmed the APPR button arms the managed approach with APP NAV and FINAL modes. They combine to FINAL APP and you can fly that down to minimums, e.g. 400ft RA if nothing else has been entered.

    Because the position of the aircraft is not as accurate using GPS the real world aircraft has not been certified for any automatic landing without ILS, So for realism sake this is also not possible in Aerofly though it would be totally doable. Our GPS is 100% accurate at the moment.