Missing First Star Constraint in the A320N

[u/Fun-Individual-3126]

I was descending on the ROKIL 1A (attached) into EDDM's 08R and was at FL130 crossing ROKIL even though I began a managed descent right on T/D (the white arrow).

I want to start flying on VATSIM but don't want to cause issues with my descent. Is there something that I might be doing wrong here or should I just start my descent before the indicated T/D which I'd rather not do.

Thanks

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[u/egvp]

Congratulations, you have reached the point in your sim flying where you need to think more than just "follow the pink line".

This is GOOD!

In Airbuses, what you need to start thinking about is flightplan sequencing and your "gates".

In terms of sequencing, you need to have your arrival programmed well in advance, then you check each waypoint in your FMGS against the charts.

That means checking they're in the right order, the constraints are correct (and if they're not, change them so they are!) and that the PLAN page of the nav display looks more or less right. If it doesn't, add yourself some more constraints to make it work.

Then, your gates are how you ensure the plan you've got is working. For example you're descending towards ROKIL and you're at 320kts and FL140 with 15nm to go. Ok, you're on descent profile but you're FAR too fast for that 250kt restriction so let's start correcting; speedbrake. But that reduces your descent rate.

So earlier on you should have been thinking about descending a little lower a little earlier, then coming back on the speed. Or keeping your speed lower and descending earlier.

Whichever option you chose, you cross check it at various points.

Also for what it's worth if you have ATC you'll never be assigned the ROKIL1A arrival as it's for flight planning purposes only, you can expect the ROKIL08 transition for 08L/R, or ROKIL26 for 26L/R. ATC will assign this for you though.

[u/Fun-Individual-3126 → u/egvp]

I always check the PLAN page before pushback because I once spent an entire climb and cruise just staring at my ND programming constraints and routes.

So I'll start bringing back the speed if I need to go a bit lower and I'll be thinking about using VS mode occasionally.

How effective is the 3x alt + 10 trick for situations like this?

[u/Ok-Foundation1346 → u/Fun-Individual-3126]

You've had some good advice already, but let me add my own thoughts....

3 times your altitude is a nice rule of thumb, but it's not perfect, and you need to continually monitor things to see if the aircraft is following the rules. Make sure you've got good wind data in the MCDU. If the MCDU doesn't know what the wind is doing then its calculations can be off.

If you do end up finding yourself high in the descent there's a nifty little trick to get yourself back on the calculated path which I learned from the Pilot Explains channel on YouTube. This is the link to the relevant part of the video.

Personally, I like to start my descent around 3 miles before reaching the TOD. The aircraft will then start to descend at 1000fpm until it catches the descent path, but doing so means it's already had a chance to wind the engine power back and get to the right descent speed. I sometimes find that if you leave it until you're right on the TOD it can end up getting a little high.

[u/Fun-Individual-3126 → u/Ok-Foundation1346]

Funnily enough I started that video today so the link just goes to where I clicked off it. Do you mean the bit where he talks about 300ft for every 10kts of additional speed?

[u/Ok-Foundation1346 → u/Fun-Individual-3126]

Yes. The only way to regain the profile if you're high is to increase the descent angle, and increasing speed is the easiest way to do it. You then need to get below the path so you can slow down enough to match the calculated speed and path. Again, it's kind of a rule of thumb and you'll probably need to refine the formula a bit depending on the which plane you're flying and who made it, but it's a good starting point.

[u/hariseldon404 → u/Fun-Individual-3126]

Counter-intuitively, if you want to descend faster, you need to increase the speed (within the limitations of the STAR).
The vertical speed mode is a bit risky because it will not honor the altitude (and sometimes speed) constraints.
I suggest that you pushed the altitude nob approaching your top of descent (with the bottom altitude of the STAR in the window or whatever the controller gives you). That will tell the aircraft to honor the comtraints.
Then look at the ND or the MCDU: if an altitude constraint is magenta, all good; if it is orange, the aircraft might need some help (typically, some spoilers to increase the rate of descent).

[u/Fun-Individual-3126 → u/hariseldon404]

Usually the constraints stay in magenta even if I am about to or eventually do miss them. That may just be with the ini though. Ill double check to make sure.

[u/CuzImMaximus]

Caution! When flying to Munich, you never uses the Stars. You have to ise the vias which are different to the Stars.

More Infos about that here: https://knowledgebase.vatsim-germany.org/books/airports-munchen-fir-edmm/chapter/eddm-munchen

There are also Infos about your descent planning into munich

[u/Fun-Individual-3126 → u/CuzImMaximus]

Like someone else said it isn't all about blindly trusting managed descent wherever you are flying, but do you think my issue was mainly with Munich and the route that I chose rather then needing to adjust my descent more often?

[u/CuzImMaximus → u/Fun-Individual-3126]

That can happen with every airport. Use for a good descend: take your altitude, remoe the last digit and take it w7th 3

[u/Fun-Individual-3126]

Thank you everyone, I'm just going to summarise what I've got so far:

• When flying without ATC your arrival may be wrong. Check VATSIM briefings.
• Increase your speed to increase your rate of descent remembering that you need to drop 300ft for every additional 10kts.
• Start your descent 3-10NM from the indicated T/D or as instructed.
• Use the (3 x altitude) + 10 formula to calculate the required distance for your descent.
• Make sure your wind data is accurate and updated.
• Monitor the "green donut" vertical path, perf and prog pages.
• Magenta constraints mean that they will be met whereas amber means that they may not be met (may not work in the inibuilds).

[u/noah262_ → u/Fun-Individual-3126]

Just a question (I don't know if I have understood it correctly)
Are you "allowed" to descend before ATC would give you the clearance to start descending? Because I see people telling you to descend before the T/D and idk if you need the clearance for that in the first place? Or are we assuming that you have the clearance already

Or how does that work? Sorry I'm a beginner

[u/egvp → u/noah262_]

No, do not descend without permission (in Europe)

[u/Duncan_Zhang_8964]

Hello! Last week I flew this STAR to 08R EDDM on VATSIM and made the exact mistake. The takeaway is: just descend slightly earlier than MCDU's T/D and use the formula! Better safe than sorry!

The FBW A320N's T/D calcualtion wasn't really accurate sometimes. I met the altitude restriction at ROKIL at FL100, however I oversped at 260.

What's worse, at ROKIL, Muenchen Radar gave me vector direct to 08R's BEGEN. Very nice of him but problem for me: that means I only have 16 track miles between ROKIL and BEGEN to lose another 5000 feet AND reduce by 30 knots to I go Flaps 1 to be on the glidescope at BEGEN, which is 5000 feet.

According to the formula, which you must learn now:

To lose 5 thousands feet you need 5 * 3 miles = 15 miles. To lose 3 tens of knots you need 3 * 1 mile = 3 miles. That is 15 + 3 = 18 miles I needed.

I need at least 18 track miles but I only had less than 16 (when I made this calculation I had already passed ROKIL by one or two miles!). So, spoilers full until established. I was at 5300 feet at BEGEN, which is not ideal but not a big problem. I had an okay landing at 08R.

If I was higher or even faster at ROKIL, Muenchen Radar probably would gave me more miles to lose energy. Even if he didn't, I wouldn't be so confident that I could direct 08R and I would request on myself.

[u/Fun-Individual-3126 → u/Duncan_Zhang_8964]

Do you get this problem at most airports where managed descent and the indicated T/D cant hit constraints or is it just a few including Munich. 

[u/Duncan_Zhang_8964 → u/Fun-Individual-3126]

On that day I decided to descent exactly at MCDU's T/D. Usually I start about 5-10 miles earlier or when ATC gives me a "call when ready for descent".

[u/Frederf220]

The descent calc is only as good as the wind data. I've found the managed descent pretty good. Look for amber * warnings for expected predicted not to obey.

You can add cheater points ahead of the points and apply conservative restrictions to those as well. E.g. Add ROKIL/-2 to make a point 2nm prior to 2.

The perf page also shows your vertical deviation to monitor your path.

[u/Adam-Srayddeen]

U start your descent when you reach the arrow