STAR profiles & ATC

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crj_705
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STAR profiles & ATC

Post by crj_705 »

In the completion of a STAR in Canadian airspace I’m just wondering why ATC controllers issue clearances to aircraft that are below STAR published altitudes, especially when aircraft are expected to comply with the speeds/altitudes unless otherwise cancelled? I understand when ATC issues ‘STAR is cancelled or cancel altitude/speed restrictions on the STAR” clearances but is it just traffic flow or MANOPS constraints that have to be manipulated for safety reasons. A big thank you to ALL controllers!
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ahramin
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Re: STAR profiles & ATC

Post by ahramin »

Maybe there's a typo in your post or I'm misunderstanding you but in Canada controllers cannot clear you to an altitude lower than the next STAR constraint. You seem to be asking why they can but that's the rest of the world, not Canada.
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wordstwice
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Re: STAR profiles & ATC

Post by wordstwice »

Actually they can clear you to an altitude below the next constraint but unless the restrictions are cancelled they must be adhered to.

For example, if there’s an intersection with a 5,000 crossing restriction ahead, the controller can still clear you to 3,000’ but you must adhere to the restriction unless it is cancelled by the controller.
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CL-Skadoo!
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Re: STAR profiles & ATC

Post by CL-Skadoo! »

We had a crew get busted for this years ago when they first started this. It was just before they started the "descend via the STAR to 8000ft" phraseology.

The way I explained it to our crews is this: You are invited over to someone's house for dinner. You still have to proceed to the front door and knock before entering. If you wish to deviate from the usual expectations, you are free to ask. However, you are not cleared to enter through an open window and take a dump in the master ensuite bathroom before sitting down at the dinner table and say "I thought you invited me over for dinner?".

Some rules may not be written down, but there is an expectation. I guess if enough people take dumps in ensuite bathrooms, they'll make a law?
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ahramin
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Re: STAR profiles & ATC

Post by ahramin »

CL-Skadoo! wrote: Sat Dec 12, 2020 12:05 pmThe way I explained it to our crews is this: You are invited over to someone's house for dinner. You still have to proceed to the front door and knock before entering. If you wish to deviate from the usual expectations, you are free to ask. However, you are not cleared to enter through an open window and take a dump in the master ensuite bathroom before sitting down at the dinner table and say "I thought you invited me over for dinner".

Some rules may not be written down, but there is an expectation.
Or you could explain it via the AIM.
9.2.3.5 Altitude Restrictions
Altitude restrictions may be included in the STAR. Although an aircraft is expected to follow the charted lateral track of the cleared STAR without further ATC clearance, as per the flightplanned/cleared route, such is not the case with the STAR vertical profile; ATC has to issue descent clearance, and when a lower altitude is issued, pilots shall descend on the STAR profile to the ATC-assigned altitude. Unless specially cancelled by ATC, all charted restrictions above the assigned altitude on the STAR remain mandatory.
I can't remember what happens anywhere else in Canada but in YVR they give you each altitude clearance as you get past each constrained waypoint. I assumed there was a reason for this and that's why NavCanada's short lived Descend Via STAR phraseology was the exact opposite of the rest of the world.
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CL-Skadoo!
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Re: STAR profiles & ATC

Post by CL-Skadoo! »

If I quote the AIM, do you expect pilots to pay attention? They hung off every word as soon as I mentioned free dinner and pooping.

It's called being an effective leader. :D
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ahramin
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Re: STAR profiles & ATC

Post by ahramin »

ahramin wrote: Sat Dec 12, 2020 9:59 am in Canada controllers cannot clear you to an altitude lower than the next STAR constraint.
Apologies, the above in incorrect. I couldn't find anything in the MANOPS and I've now been told that while it's poor practice to clear an aircraft below a STAR altitude since "pilots bust them all the time", it's perfectly allowed.

So back to the original question, why is it allowed? I guess because the more predictable an arrival is and the less talking required to do so, the safer and easier the arrival will be. Fewer buttons pushed, both on the FCU/MCP and the mike.
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ahramin
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Re: STAR profiles & ATC

Post by ahramin »

CL-Skadoo! wrote: Sat Dec 12, 2020 12:37 pm If I quote the AIM, do you expect pilots to pay attention?
Well yes, it's called being a pilot. :)
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frog
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Re: STAR profiles & ATC

Post by frog »

I really like the dinner metaphor !
I'll remember that ! :)
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CL-Skadoo!
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Re: STAR profiles & ATC

Post by CL-Skadoo! »

For clarification, through my interactions with controllers, the trouble came most often in this scenario:

ATC clears you to 8000ft. The arrival you are on has a restriction that indicates "XXXXX point between 15,000 and 17000ft". People would hustle on down to 8000ft and completely disregard the crossing restriction. The perception was, obstacle clearance was no factor, so pilots were free to head down. Except that gate was there to manage the airspace better, not provide obstacle clearance. To combat this, they added the phraseology "descend via the STAR to 8000ft" and ATIS messages were programmed to also remind pilots to do just that. It added a ton of extra words to every transmission and ATIS messages. No one liked it and seems to have been dropped.

The thing is, you're always descending via a STAR until explicitly told not to. So back to the poster's question, why do that? Ahramin's statement of frequency congestion is a major factor, plus, a lot of the time, the crossing restriction and that final terminal altitude are tight; aircraft could be left high when things are busy. Send them down, expect them to cross their gates, and hand them off; much easier.
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lostaviator
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Re: STAR profiles & ATC

Post by lostaviator »

ahramin wrote: Sat Dec 12, 2020 12:23 pm I can't remember what happens anywhere else in Canada but in YVR they give you each altitude clearance as you get past each constrained waypoint. I assumed there was a reason for this and that's why NavCanada's short lived Descend Via STAR phraseology was the exact opposite of the rest of the world.
Usually, but these are interesting (And quiet) times. Got cleared to 3,000 and cleared the approach on initial call with arrival a few months back. There used to be a blurb on every chart about STAR restraints being required, but they seem to be taking those off as they republish the fancy colour charts. I can definitely see our way of doing things confusing to foreign carriers and this causing some issues. I'm sure our American friends upfront look at each and wonder what "descend 3,000" means the same way we look at each other and wonder what "descend 3,000" means when flying down there. The same words mean completely different things.

OK. Now let's talk about cancelling all the altitude restrictions and then having us fly a 20 mile downwind. :lol:
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Braun
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Re: STAR profiles & ATC

Post by Braun »

lostaviator wrote: Wed Dec 16, 2020 7:57 am
ahramin wrote: Sat Dec 12, 2020 12:23 pm I can't remember what happens anywhere else in Canada but in YVR they give you each altitude clearance as you get past each constrained waypoint. I assumed there was a reason for this and that's why NavCanada's short lived Descend Via STAR phraseology was the exact opposite of the rest of the world.
Usually, but these are interesting (And quiet) times. Got cleared to 3,000 and cleared the approach on initial call with arrival a few months back. There used to be a blurb on every chart about STAR restraints being required, but they seem to be taking those off as they republish the fancy colour charts. I can definitely see our way of doing things confusing to foreign carriers and this causing some issues. I'm sure our American friends upfront look at each and wonder what "descend 3,000" means the same way we look at each other and wonder what "descend 3,000" means when flying down there. The same words mean completely different things.

OK. Now let's talk about cancelling all the altitude restrictions and then having us fly a 20 mile downwind. :lol:
Devil's advocate but most time I cancel the restrictions the aircraft ends up being to high to turn in at the correct point anyways. I usually just cancel the speed restrictions, that way you can get low and fast and ready to turn more quickly.
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