OnCourse Software

Here's a short take on Oceanic ATC procedures...I have thousands of hours of hang time over the water working ATC on HF radio.

First, it's important to understand that there are three parties to Oceanic air traffic control: ATC, a separate radio communications facility operated by ARINC International, and the pilot. ATC and ARINC talk to each other by phone or computer--they are not sitting next to each other. So the guy you're talking to is an intermediary to ATC, not the guy doing air traffic control.

Second, SELCAL is used as an electronic tool to poke the crew of a particular jet. The 4-letter SELCAL code is unique to each airplane, and when AIRINC transmits those tones, it sounds an alert inside the aircraft to let the crew know their presence is requested on the HF ATC frequency. SELCAL is ONLY used by ARINC when it needs to initiate a communication with an airplane. Aircraft do not have the capability to send SELCAL tones.

So initial contact by the crew with Oceanic ARTCC usually involves estimating their arrival at the first reporting point, and a SELCAL check to make sure their alerting system is working. Once they verify it's working, they can "punch off" the HF radio when they're not actively talking so as to not listen to hours of scratchy hissing HF noise. An initial contact might sound something like this:

Pilots: Gander Radio, SPAR76 estimating five-zero north, five-zero west at 2235, flight level three five zero, request selcal check Alpha-Delta-Quebec-India, over
Gander ARINC: SPAR76 Gander radio, copy five zero north five zero west at 2235, flight level three five zero, standby selcal check
~20 sec later: two sets of selcal tones, at which time the alerter beeps in the aircraft
Pilots: Gander, SPAR76 selcal checks good.
Gander ARINC: SPAR76, Gander roger, call me at five zero north.


It's important to note that any time the pilots initiate a call, SELCAL is not needed as the crew is obviously talking and present on the frequency. Again, SELCAL is only used by AIRINC to initiate a call with a crew that is not currently talking to them.

So at 50N 50W, the crew makes a position report. No SELCAL is involved here.

Pilots: Gander radio, SPAR76 position
Gander ARINC: SPAR76, go ahead with your position report
Pilots: SPAR76 checked five zero north five zero west, 2234, flight level three five zero, mach decimal eight five. Five zero north, four zero west next at 2315. Five zero north three zero west next.
Gander ARINC: Gander copies SPAR76 checked five zero north five zero west, 2234, flight level three five zero, mach decimal eight five. Five zero north, four zero west next at 2315. Call me at four zero west.


Now here's how an ATC request might work. Remember...you're not talking to ATC, you're talking to an intermediary, so he can't give you anything straight away.

Pilots: Gander, SPAR76 request
Gander ARINC: SPAR76, Gander, go ahead with your request.
Pilots: SPAR76 requests climb to flight level three seven zero.
Gander ARINC: SPAR76, Gander copies your request to climb flight level three seven zero. I'll call you back.

Now the pilots can punch off HF while Gander ARINC calls Gander ARTCC to make the request. Some time later (generally 2-5 minutes, sometimes longer if they're busy) Gander gets the clearance from ATC and sends SPAR76's SELCAL tone to get their attention.

two selcal tones are heard
Pilots: Gander, SPAR76 answering SELCAL
Gander ARINC: ATC clears SPAR76 to climb to flight level three seven zero, report reaching.
Pilots: SPAR76 cleared to flight level three seven zero, will report reaching.


So that's how SELCAL is used, and how ATC is done on HF radio.

Cheers

Bob Scott

Thanks for that Bob, very interesting indeed. So we haven't got it far wrong then?

Our emulation of Oceanic Control was first included way back with PFE V2 and it was as a result of a request from a RW pilot. I agreed to implement it but only if he provided me with exact requirements. So working with his help and what we had available we came up with what I thought was a new a very unique feature for ATC simulations.