Top of decent a320 keeps moving

1st Official Post
    • Official Post

    Hi Mark,

    there are multiple "top of descent" arrows in the A320. When you are at cruise altitude (ALT CRZ displayed on PFD) then the TOD should be a fixed point and I recently confirmed this in the Steam version. Once you are in the descent another arrow is shown, this indicates the next "top of descent" where the aircraft expects you to push the altitude button again to continue with your descent. This is of course dependent of your selected altitude but a blue level off arrow should mark the end of the descent and the white continue descent arrow, so to say, is right next to it.

    Is this what you observe?

    When you are in the descent the top of descent arrow (start descending arrow?) is moving when the selected altitude is changed. A blue level off arrow can be seen near it.

    Quote from markmcfckeohane

    Hi newb question and flight simmer here when I set my altitude before top of decent the top of decent arrow keeps moving as i move the altitude knob up amd down anyone know what I'm doing wrong

    Cheers in advance

    Mark

    Same here and afaik it 's not as it should be. The TOD should be a fixed point. I posted about this before: when I am cruising and want to already set my descent altitude before the TOD, and so before starting the descent, the TOD moves away when I dial in a lower altitude. And when I raise the altitude again, before starting the actual descent, the TOD moves closer again. Problem here also is that as soon as I set my desired altitude I have lost my actual TOD and don't know exactly when to start the descent anymore.

    During descent I do see a blue and white arrow 'in the distance' but the white one usually isn't next to the blue one. I also always descent directly to my final altitude so there is no need to press the ALT button again and hence there also shouldn't be a white arrow in the distance, it seems to me.

    Some thoughts concerning that moving TOD: it is a bit hard to explain in English for me but it seems that the current system of the AP is looking at the altitude which is shown in the altitude window and NOT the altitude at which the plane actually is flying. So imagine I am flying at FL220: obviously the ALT window also shows FL220. In this situation the TOD is calculated and shown on the ND. But when I change the ALT (just in the window!) it looks to me the TOD is being calculated again. So let's say I change the altitude to FL180 (just in the window!): when I do so the AP system (and by that I mean the AP system as created by IPACS, not the original Airbus system!) recalculates the TOD again 'on the fly' and shows you were the TOD is IF you would be flying at FL180. I hope you know what I mean... ;) If I set an altitude of 12.000 ft the TOD moves to the spot where I should start descening IF I was actually flying at 12.000 ft. And so on. If I change the altitude back again to FL220 the TOD is once again where it should be for my actual altitude. I hope I make some sense here. ;)

    In other (and less) words: it seems the TOD isn't linked to the actual altitude the plane is flying at, as it should be, but it is directly linked to the altitude set in the ALT window. This is why changing the altitude alone already changes the TOD. And afaik this is not right.

    • Official Post

    Hi,

    then something else is messed up. Almost sounds like as if you are in the wrong flight phase for some reason. When I am in cruise the tod is fixed as it should be only in the descent and approach phase it is moving, but that is not really the top of descent, just the I'm leveling off here, continue your descent at this point if needed...

    I'm looking into it.

    During my flight, after reaching the TOC, only the first white TOD that appears is fixed. Changing the altitude won't move it. Let's say I then descend and arrive at 6000ft a new TOD will appear. That one is variable and will shift up or down when changing the altitude knob (not engaging it). I have to admit, I do have some doubts how to interpret that new TOD arrow though.

    I do this alot, descending to a somewhat higher altitude, to emulate ATC instructions or a holding pattern, before descending to approach and then capture the localizer/glideslope.

    Edited 8 times, last by Stringer (August 10, 2017 at 1:48 PM).

    • Official Post

    Hi,

    well for that you would use the intercept arrow... That is not implemented yet, sorry.

    The new TOD should descent and as soon as you level off it is gone and at another location (affected by selected altitude).

    I think I can interpolate the intercept arrow now, might need a bit of trial and error to get it working (assumes half speedbrakes from above, etc...)

    Regards,

    Jan

    • Official Post
    Quote from markmcfckeohane

    yeah mine never hits alt cruise just hold at alt when i put my alt in for decent the white arrows just moves

    Ahh, then you are probably just too low...

    If you set your aircraft on the departure runway the correct altitude is set as selected altitude. Then it reaches the cruise phase.