APPR mode - vertical speed

HI,
does anybody know why with some airbus, when I turn on the appr mode, it doesn’t adjust the altitude. I have to let the VS on so that appr mode can work, but. if for example the VS is on 0, then the aircraft won’t change altitude. It line up with the runway, but I have to adjust my VS so that I arrive at the beginning of the runway. Is this normal ? Do you have any reasons or solutions ?

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Have you checked out this Tutorial?

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Yes,
but in the video it says (at 1:43) that the aircraft will begin descending at the appropriate time. It means that the aircraft controls itself the VS. Sometimes it don’t. The aircraft doesn’t descend to the appropriate VS, it just follow the value in the AP. If I put a positive VS, the aircraft climb ! If the valu descend but not enough (for example -200/mn) the aircraft will touch the ground too late, maybe further the runway. To avoid this, I always adjust the VS, but I simply don’t understand why the computer doesn’t do it. Maybe I should just wait, don’t touch anything and let it do. I’ll try do to this one time, to see if the problem comes from me.

Are you sure that you selected the correct runway as NAV1?

@NoahBe set it as your intercept altitude, no need to change the VS. For example, if you are intercepting @3000, descend and maintain that altitude. Then, APPR won’t do anything until capturing the GS, where it will start descending with it.

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APPR will maintain what is set until you intercept the slope. For example if the glideslope is in font of you are 3k feet, and you have AP set to 2500, it will maintain that until it hits.

A video with your hud may be the best to avoid people guessing.

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yes i’m sure, but I think I found a reason. When I activate APPR mode, I had my VS on, but my A/P for the altitude wasn’t activated, and if I activate it, the approach work perfectly.

I thought of making a video too late, the message had already been sent, but I will do it next time, thank you. If you don’t want to, I can make a video that shows with and without the ALT set, so you can see the difference. Tell me if it might be helpful.

I found the solution: the VS must be enabled, but ALT too. If the altitude is set (whatever altitude), the aircraft will descend correctly immediately. If the altitude isn’t activated, the aircraft will firstly descend at the VS set during a moment, and it will adjust vertical speed after. Like I didn’t want to fail my landing, I always adjusted by myself the VS using the FPV to be sure that I would arrive at the entry of the runway. Thanks to everyone who responded and tried to help me.

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i think you must set your VS to 0, so that you can use it .

I think an additional issue is that if you are descending and are always slightly below the glide, APPR will fail to capture the glideslope. Hence you have to be careful that you actually cross the glideslope at some point with APPR activates for it to work in IF.

It’s worth bearing in mind that the intercept altitude will be marked on the chart relevant to the approach you are using. It will always bring you down to a “stop altitude”, such as 3000ft, then you fly at that altitude until you intercept the localiser from below. This altitude is what should be set in your altitude window (unless you have been instructed by ATC to do something different to the charts) in order to avoid false slopes!

APPR has been acting up since this update came out.

This happens if you descend using VNAV. It confuses the program and results in it trying to hold the last altitude the VNAV was set too.

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