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Procedural service

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Procedural service

Old 10th Feb 2014, 11:53
  #1 (permalink)  
Thread Starter
Join Date: Jun 1999
Location: UK
Posts: 63
Procedural service

Is an arc procedure to ILS come under this and if so, if an aircraft 7 miles ahead is cleared to perform such a procedure why wouldn't a slow moving aircraft be also cleared for the same or would the slowing moving aircraft fly to the overhead then outbound for the ILS?

Just wondering what distinguishes between them for briefing purposes.

SkidSolo is offline  
Old 10th Feb 2014, 13:34
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Join Date: Jun 2001
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In the absence of any other information, if the aircraft is cleared to follow the published procedure (rather than being vectored) then, yes, it is receiving a procedural approach control service.

I'm not current on this sort of thing so someone doing the job on a daily basis may correct me but most arrival procedures do not make allowance for differences in the speed of aircraft. ATC has a 'landing interval' which, essentially, is the minimum interval between aircraft leaving fix to fly the approach. What happens to other aircraft that are later in the approach sequence depends on a bunch of other things including other traffic and how easy is is to hold an aircraft (for both pilot and controller) in a good place to start the arc procedure. Remember the controller has to keep subsequent aircraft in the approach sequence separated from departing aircraft, the one flying arc procedure and the missed approach for the arc procedure. For this reason it may not be ideal to let the second aircraft in the sequence run to the overhead.

There may be some local separations that the controller can use but that the pilot probably doesn't know about - things like if aircraft A is in the NE sector and more than 15D it is separated from traffic departing runway xx and joining route Y. It is all based on local routes and the navaids that are available - such separations are known as 'deemed separations'. These deemers are typically calculated using rather complex formulae in an ICAO doc that is only truly understood by mystics and the like who mutter phrases containing words like 'containment area'.

I'll stop rambling now but I thought I'd share a glimpse into the controllers' murky world of procedural control!
LookingForAJob is offline  
Old 10th Feb 2014, 19:10
  #3 (permalink)  
Join Date: Jun 2001
Location: southampton,hampshire,england
Posts: 836
Difficult to answer without a better idea of the scenario. It would be possible for the lead aircraft to be cleared for an approach of any type [with or without arc] and for a second following aircraft to also be cleared for the same approach BUT with limitations. The controller must be able to demonstrate or prove that some form of separation is in force at any stage in the process.
I used to do this sort of thing: first a/c cleared for VOR approach at 3000 feet, second a/c cleared for VOR approach at 4000 feet.....first a/c reports inbound leaving 2000 feet descending, clear second a/c to 3000 feet....controller uses vertical separation initially and can change to alternate separation methods such as visual separation or unambiguous position reporting to confirm traffic have passed to the prescribed degree [could be DME/reporting point/marker/NDB]....
Even the most modern approach techniques such as "point merge" do not differ too far from the basic principles and practices used successfully for decades.
Have a google look at "AIC Directory Irish Aviation Authority"...look up year 2011, NR 05/11.......it is the easiest way to understand point merge....and coming to the UK very soon.
055166k is offline  
Old 28th Feb 2014, 08:40
  #4 (permalink)  
Join Date: Jan 2012
Location: Nowhere
Posts: 16
I have to admit I don't quite understand your question, but as a procedural app/twr controller I'll explain my separation(I hope this is what you mean).

We use VOR STARs from entry point until Intermediate Fix, where the aircraft should start intercepting the ILS. The most used STAR doesn't have an ARC DME, but we have a couple that have.
First let's take the non ARC procedure. I know with a 0.5-1 minute error the time it takes an aircraft to reach the IF from entry point via STAR. So what we usually do is put 4-5 minutes between them and the first is authorized for STAR, the second descends min STAR FL+1000 ft and from a point approve STAR. I can also restrict the descent to a minimum altitude, providing separation from the STAR, until the first aircraft is ILS established.
Second, ARC procedure. We usually approve normal STAR for the first and second descending to separation FL on course to the VOR and the issue a different STAR from VOR to IF. This way the first has enough time to establish.

If you have(we don't), use points to separate. Let's say you have ABC point prior to IF(point that maintains separation ofc). You can approve ILS for the first one and the second approved ILS via ABC. It depends on your control zone.
You can always ask for position reports or if you have them in sight tell them(here at least it's a controller based separation) or have them separated from each other if they see each other.

Hoped I helped a little.
elafrican is offline  
Old 28th Feb 2014, 16:11
  #5 (permalink)  
Join Date: Sep 2008
Location: UK
Age: 37
Posts: 13
Hi, I'm going to guess that as you say UK in your profile your looking for a UK answer.

A procedural service is the ATsocas service you are operating on, normally if your flying a procedure you would be on a procedural service but not necessarily, you can fly a procedure on a basic service.

The reason you weren't given the arc was probably that the controller didn't think he could give you decent early enough to facilitate a stable approach I.e having to keep you a 4A until Loc established. By giving you the overhead he has built in an extra couple of minutes/miles to allow earlier decent. I would advise speaking to the tower either by phone or pop over for a visit as they will give you a local answer.

As to what to expect it really depends on too many factors to give u an easy rule. I will always try to give expected app on first contact but speak to your local unit and they will be happy to help.
Sligu is offline  

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