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Author Topic: Clearance/Ground Question  (Read 11184 times)

Offline BrianCLT

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Clearance/Ground Question
« on: May 30, 2006, 07:14:21 PM »
I am an instrument pilot and am interested in listening to IFR clearances. Since all airline flights are on IFR flight plans (because they all fly above 18,000 where an instrument flight plan is required) it seems as if I would hear a clearance for every airline flight. But when listening to say Boston clearance/ground, it seems as if I hear very few of them. I get one every once in while, but nothing near the amount of flights pushing back. Anybody know why? Am I missing something?

Thanks!



Offline davolijj

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Re: Clearance/Ground Question
« Reply #1 on: May 30, 2006, 08:19:32 PM »
Most airlines these days utilize pre-departure clearance (PDC).  It's an automated system that interfaces with the ACARS equipment onboard the aircraft and the FDP/FDIO system in the ATC facility.   So the reason you're not hearing clearances read over a traditional clearance delivery VHF frequency is because they're mostly automated now.

Offline BrianCLT

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Re: Clearance/Ground Question
« Reply #2 on: May 30, 2006, 08:50:17 PM »
Most airlines these days utilize pre-departure clearance (PDC).  It's an automated system that interfaces with the ACARS equipment onboard the aircraft and the FDP/FDIO system in the ATC facility.   So the reason you're not hearing clearances read over a traditional clearance delivery VHF frequency is because they're mostly automated now.
Bummer.

What feeds are there that might have a lot of GA action that has clearance/ground frequencies monitored?

Offline KSYR-pjr

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Re: Clearance/Ground Question
« Reply #3 on: May 30, 2006, 09:30:52 PM »
But when listening to say Boston clearance/ground, it seems as if I hear very few of them. I get one every once in while, but nothing near the amount of flights pushing back. Anybody know why? Am I missing something?

Just as a sanity check, are you sure that you are hearing Boston clearance delivery and not Boston ground?   At Boston Logan, the two ATC positions are definitely discreet frequencies.   

Perhaps you are, but your continued reference to "clearance/ground" and your reference to "pushbacks" have me curious. 
« Last Edit: May 30, 2006, 09:32:35 PM by KSYR-pjr »

Offline BrianCLT

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Re: Clearance/Ground Question
« Reply #4 on: May 30, 2006, 09:52:59 PM »
But when listening to say Boston clearance/ground, it seems as if I hear very few of them. I get one every once in while, but nothing near the amount of flights pushing back. Anybody know why? Am I missing something?

Just as a sanity check, are you sure that you are hearing Boston clearance delivery and not Boston ground?   At Boston Logan, the two ATC positions are definitely discreet frequencies.   

Perhaps you are, but your continued reference to "clearance/ground" and your reference to "pushbacks" have me curious. 

Well, it is listed as "clearance/ground." So I am assuming if I choose that feed that both are being monitored. It lists the clearance frequency as 121.65 and ground as 121.9/121.75, and I am assuming that feed monitors them all. I do hear ground for sure, and every once in a while I will hear an IFR clearance. It is probably a GA plane getting their clearance.

Offline davolijj

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Re: Clearance/Ground Question
« Reply #5 on: May 30, 2006, 10:24:01 PM »
...I do hear ground for sure, and every once in a while I will hear an IFR clearance. It is probably a GA plane getting their clearance.

Still, there's enough Cape Air and International activity there....the clearance delivery frequency should be pretty busy.  And the feed does scan just what's listed (it's one of my favorites).  I haven't been able to listen as much as I'd like lately but last I knew there was plenty of clearance delivery action.

Offline w0x0f

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Re: Clearance/Ground Question
« Reply #6 on: May 31, 2006, 12:34:00 AM »
Good question, Brian.  Not everyone is familiar with PDC.  It makes life a lot easier on the clearance delivery person.  One other thing.  Not all airline flights go above FL180.  Some short hops stay lower.  A pressurization problem would also require a lower filed altitude.

w0x0f

Offline KSYR-pjr

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Re: Clearance/Ground Question
« Reply #7 on: May 31, 2006, 07:57:08 AM »
Well, it is listed as "clearance/ground."

I see.  You are referencing the feed title, not the frequency title.  Being an IFR pilot, you know that most class D towers (at least in the US) combine clearance delivery and ground onto one frequency.  I mistakenly assumed that you were under the impression that Boston, as a class B airport, did this, too.  Sorry 'bout that.  :)

So I am assuming if I choose that feed that both are being monitored. It lists the clearance frequency as 121.65 and ground as 121.9/121.75, and I am assuming that feed monitors them all.

Correct.  However, given that there is one scanner monitoring both frequencies, it is possible that you are hearing a long run of busy activity on the ground frequency and that is dominating the feed.

In no way do I mean to undermine Dave's explanation about the PDC, but as a pilot who routinely flies into Boston Logan for Angel Flight missions, I can tell you that Boston CD does contain a lot of clearance issuances and readbacks, both from GA (corporate being the largest percentage here) and commercial airlines.
« Last Edit: May 31, 2006, 09:04:03 AM by KSYR-pjr »

Offline BrianCLT

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Re: Clearance/Ground Question
« Reply #8 on: May 31, 2006, 08:48:11 PM »
Most airlines these days utilize pre-departure clearance (PDC).  It's an automated system that interfaces with the ACARS equipment onboard the aircraft and the FDP/FDIO system in the ATC facility.   So the reason you're not hearing clearances read over a traditional clearance delivery VHF frequency is because they're mostly automated now.
I was just listening and heard one of the pilots mention PDC. I wouldn't have known what it was or even paid attention to it if you hadn't mentioned it in your post.

Offline davolijj

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Re: Clearance/Ground Question
« Reply #9 on: May 31, 2006, 09:08:05 PM »
 :wink: