What went wrong during my decent?

So I was cruising at at 31,000ft from Sydney (YSSY)
to Melbourne (YMML) on an Airbus A380
I was using BOYS7A STAR to decent as you can see

My decent to the waypoint with 9000ft went smooth and my speed was 220 knots but as soon as I started my decent to the waypoint with 6000ft the plane just went into a VS of -2000 and pushed my nose extremely down causing me to over speed and almost get a violation before I disengaged autopilot, I later had to go around and then land.
(also another small thing to note- I changed the altitude at the waypoint from 6000ft to 5000ft because I thought it would be hard to loose 3000ft on the following waypoint but later I also did the same flight in solo but with the altitudes given in the STAR and the same thing happened but worse)

So what went wrong? I would really appreciate if someone answers :D!

Don’t trust the constraints given to you in infinite flight. Read them as published, Australian charts are free from Air Services Australia.

  1. This is not a jet arrival, you should’ve filed a different procedure.

  2. The altitude constraints for Infinite Flight do not tell the whole picture. Notice how the altitudes of the fixes are shown as between those published altitudes. You should adjust to be between them to plan for a smooth descent.

  3. Between ANBEL and NEFER you’re looking at 9nm. If you’re zooming at 230-40ish when correcting for ground speed, that’s just a little over 2 minutes of flight time. You have to lose 3000 feet in that span of time, so its going to target a higher VS of >-1500, along with how slippery the aircraft is it’s going to speed up, leading to a higher VS again, so it’s a negative feedback loop.

Tldr: descend earlier to be in between the altitudes, not riding the top edge of the descent profile

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The reason your plane descended like that is because your plane is trying to descend 3,000 feet in 7nm. Thats WAY to much, Typically on approach you should descend 1000feet for every 3nm miles under 200kts.

I would highly recommend checking your FPL every time to make sure it’s within the correct perimeters. Don’t always take the altitude points in a STAR for granted.

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Oh I get it thanks :) also can I get more of these charts outside Australia and if I can then how can I find these?

Oh, Alright :) Thanks! That means I have to change the altitudes on the STAR if I’m not wrong

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Yep thats correct 👍

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I use Navigraph, but there are other apps.

Also, always remember to not just let.VNAV do its thing. You need to be monitoring it. You have options: speedbrakes, flaps (if you reduce your speed enough which also helps in itself), or even just reducing the V/S and knowing you won’t make the “restriction”. If you were generally too high for the approach overall you could give yourself more track miles by going onto a radar vector or changing the programmed routing.

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oh yeah! but those charts cost money :(

Yeah navigraph is a subscription, but the charts are often available on other apps/places like said above.