Why does my aircraft start swaying whenever I’m on final?

2 days ago, I used APPR to land a 787-10 on RW09R at EGLL. The Dreamliner started swaying and was decreasing altitude at a high rate and ended up crashing. Today I was on final RW22R at KJFK and the same thing happened with the A330-900neo. Can someone please explain to me why this is happening?

This is usually due to speeds which are too low on final approach, the aircraft will not necessarily stall, but won’t have enough lift to continue with a -800ft/min descent rate.

I have several questions to try and better locate the issue:

  1. What speed do you usually approach at ? (final approach speed)
  2. Do you use flaps on final ?

I’ll already give the answer to gain some time:

  1. In heavy aircraft, try landing at around 140-150kts
  2. 30° of flaps in the 787, Full on the Airbus.

Cheers, hope this helped!

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This sounds interesting, but a plane would never crash if the APPR is correctly locked.
(But actually yeah as everyone said you have to input correct flaps and speed or you may STALL)

Make sure every time you enable it, The ‘LOC’ and ‘GS’ turn are properly engaged an hence turn Green.

Maybe this would help…

It’s possible and all about your speed settings. If the plane is still at a high weight and the speed is to low, even with the right settings it’ll most likely stall out. Another factor is Airport elevation, temperature and air pressure.

Your speed is too low

Hi, in your title you stated “whenever I’m on final,” and in your post you said

So does this loss of control usually occur even when you’re not using APPR?

No, but when I tried to calibrate and disconnect APPR, it became worse

The speed for 140.

I have been using the APPR feature and this has never happened before

Please share a replay next time this happens, it will help identify the issue, but I’m confident that speed was the issue.

I have the replay right now let me get it.

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Share My Infinite Flight Regardez-le

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Ok so I took a look at the replay, and the issue is quite obvious:

  • Speed is 139 kias
    Flaps 1+F setting is really not enough at this speed
    Flight spoilers were extended
    You’re flying an A339 which is a heavy aircraft

The settings stated above mean that you clearly did not have enough lift, you basically stalled out.

Hope this helped, next time, try putting down the flaps as stated in my original message

And don’t extend the spoilers as such slow speeds, even more so in the A330 as they extend and retract very slowly.


Merci pour votre aide, Mathurin

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Avec plaisir !

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Problem solved