"Descend Via" Clearance when already below the next restriction

[Nick]

An airplane is flying a STAR at 17000' as a cruise altitude on a short flight (for instance IAD-EWR).

ARTCC clears the aircraft to "descend via the arrival."

However, the next fix on the arrival, DQO, has an altitude restriction of "At or above FL200."

Should a controller expect the aircraft to wait until after DQO to start down for a subsequent fix (13000') or is it legal and possible for you to start down before DQO since you are already at 17000?

Looking for an actual source in writing from the AIM or 7110 if anyone knows where it may be buried. Thanks!

 

[Autothrust Blue]

An airplane is flying a STAR at 17000' as a cruise altitude on a short flight (for instance IAD-EWR).

ARTCC clears the aircraft to "descend via the arrival."

However, the next fix on the arrival, DQO, has an altitude restriction of "At or above FL200."

Should a controller expect the aircraft to wait until after DQO to start down for a subsequent fix (13000') or is it legal and possible for you to start down before DQO since you are already at 17000?

Looking for an actual source in writing from the AIM or 7110 if anyone knows where it may be buried. Thanks!

The "DESCEND VIA" phraseology is here in the AIM (5-4-1). Are you ON the RNAV STAR, or are you cleared "direct DQO, descend via ...?"

(I think that this isn't directly addressed if you're already on the STAR track and below the "At or above". I personally would key up and ask what they want me to do.)

 

[Nick]

The "DESCEND VIA" phraseology is here in the AIM (5-4-1). Are you ON the RNAV STAR, or are you cleared "direct DQO, descend via ...?"

(I think that this isn't directly addressed if you're already on the STAR track and below the "At or above". I personally would key up and ask what they want me to do.)

The airplane is on the arrival, and gets descend via while already below the minimum altitude for the net fix.

 

[Autothrust Blue]

The airplane is on the arrival, and gets descend via while already below the minimum altitude for the net fix.

Roger that.

 

[GypsyPilot]

I think that's a good question, and is similar to one I had going into Denver the other day. We were on the FRNCH ONE.GWEDO. We were on the arrival (already passed GWEDO), and then cleared PD to F270. We got switched to another controller after starting our descent to F270, and checked in as such (e.g. Flight Level 35.8, discretion F270). The new controller said "Descend via the FRNCH ONE arrival". We weren't sure if this was after descending to F270, or if we had to now meet the restrictions above F270. We asked, and were given a very terse "You're cleared to Descend via the FRNCH ONE!". We were still in a position to meet the other restrictions, so just did so.

But we were wondering what would happen if we had already descended to F270... It was our discretion to do so earlier, so would we now have to climb back up?

 

[mikecweb]

Whenever I've gotten something like this the controller usually starts with, comply with previous restriction then descend via...

 

[Autothrust Blue]

Whenever I've gotten something like this the controller usually starts with, comply with previous restriction then descend via...

I think it's *supposed* to be cross (____) at (___) then descend via, from reading that part above. How it's actually done is a mystery.

 

[GypsyPilot]

Whenever I've gotten something like this the controller usually starts with, comply with previous restriction then descend via...

Exactly, which is why we were both confused. I was just surprised she got snippy with use when we asked for clarification.

 

[mikecweb]

Exactly, which is why we were both confused. I was just surprised she got snippy with use when we asked for clarification.

Ask for a phone number and talk to the sup.

 

[GypsyPilot]

Ask for a phone number and talk to the sup.

Yeah, normally I would've. But it was one of those hellish trips, we were tired, almost done, and just didn't care enough at the time. The past two weeks of December were rookie season, and it was very tiring!

 

[BWER]

As a controller I would do one of two things in this situation. First, clear you direct to a fix that you are not below the at or above altitude.

Second, clear them to cross a fix down the road at their present altitude then descend via.

Lots of gray areas.

Sent from my SGH-I747 using Tapatalk 2

 

[trickeriche]

I know every time I've flown IAD-EWR, they file us:
IAD..SWANN.V445.DQO.PHLBO3.EWR

With this routing, you would not be on the arrival until DQO, therefore, descend via would not apply until
passing DQO. At least that's my take. Plus, who wants to get that close to Philly anyway?

 

[Bernoulli Fan]

I think that's a good question, and is similar to one I had going into Denver the other day. We were on the FRNCH ONE.GWEDO. We were on the arrival (already passed GWEDO), and then cleared PD to F270. We got switched to another controller after starting our descent to F270, and checked in as such (e.g. Flight Level 35.8, discretion F270). The new controller said "Descend via the FRNCH ONE arrival". We weren't sure if this was after descending to F270, or if we had to now meet the restrictions above F270. We asked, and were given a very terse "You're cleared to Descend via the FRNCH ONE!". We were still in a position to meet the other restrictions, so just did so.

But we were wondering what would happen if we had already descended to F270... It was our discretion to do so earlier, so would we now have to climb back up?

Apologies for my colleague being terse, but any new altitude clearance issued (descend via the arrival) supercedes previous altitude clearances and restrictions, unless restated. The controller likely observed you were still in a position to descend via the arrival and told you to do so.

 

[GypsyPilot]

It's what we thought, but just wanted to clarify it. Not sure why she had a problem with it. I've done a lot of RNAV arrivals, and controllers are usually good about preventing a confusing clearance. More importantly, they're usually good about clarifying misunderstandings.

 

[Vector4Food]

Speaking from experience, if you issue vague instructions which contradict a published restriction, expect the pilot to either muck it up or ask questions, hopefully the latter.

I don't blame you for asking the question, personally even though I know what you're supposed to do, i guarantee you're not the first one to ask that question in that airspace.

Personally, my clearance would have been "Maintain 17,000 until DQO, then descend via the arrival" or something to that effect

Ambiguity is a dangerous thing with anything ATC related

 

[Cav]

I used to fly the IAD-EWR route often and more often than not it seemed the controller would issue a clearance like, "After DQO descend via the PHLBO2" which took all the guess work out of it which basically told me that they either acknowledged the grey area, have had problems in the past, or tired of answering the inevitable follow up question! Perhaps a little bit of all 3. Good question though. I tend to think the answer lies in trickeriche 's post above re: the filed clearance.

 

[Cav]

Looks like canadian_atc stole my thunder I know in practice I would probably remain at 17k even without a more clearly stated clearance until passing the higher restricted fix.

 

[Vector4Food]

I used to fly the IAD-EWR route often and more often than not it seemed the controller would issue a clearance like, "After DQO descend via the PHLBO2" which took all the guess work out of it which basically told me that they either acknowledged the grey area, have had problems in the past, or tired of answering the inevitable follow up question! Perhaps a little bit of all 3. Good question though. I tend to think the answer lies in trickeriche 's post above re: the filed clearance.

Might work on that/some routes.

A lot of places, if you file that, you'd be re-routed back over the initial fix