San Francisco Radio with Sun Country 504

[Gunslinger36]

I'm not sure if this is the right forum, but I wanted to share a spot that may be of interest. At 01:38Z on 4-04-16, I copied Sun Country 504 calling San Francisco Radio on 129.450 MHz with a request for an HF radio and SELCAL check. I did not copy the ground station but could copy Sun Country 504 quite well on VHF. From the pilot's read back, I copied that San Francisco Radio provided a frequency of 11342 kHz for the HF radio and SELCAL check. I was able to copy both stations on HF at approximately S-6 to S-7 signal. This is of particular interest to me because my monitoring location is central Missouri. I had made the assumption that AIRINC did not provide any HF coverage to the mainland United States, but only provided HF coverage to oceanic areas. VHF over the mainland is obviously primary, but apparently they have secondary HF capability over the mainland as well. A further check on FlightAware shows that Sun Country 504 was over south east Kansas at the time of the HF call to San Francisco.

 

[invergordon]

I would imagine that company requires crews to check on HF for compliance so that should the aircraft need to use HF that the airline has a record of function checks. And who better to do this with than ARINC. I see that this aircraft (N821SY) has traveled to the likes of Latin America so there could be a need for HF to be used on what may be a more regular basis than perhaps a CONUS scanner might think.

 

[ai8o]

A very common practice.
SUN 504 was probably going somewhere over the ocean or outside of ARINC's VHF coverage.


I am in North Carolina near KCLT.

I hear Commercial aircraft leaving KCLT and KRDU that are going to destinations outside the USA Check their SelCalls in just this manner on the local ARINC channel.

A SelCall long check before hitting Oceanic Air space served two functions,
one it verified to ARINC SF that they were indeed moving and needed to be tracked,
Two, the test verified that the SelCall RCVR and the HF XMTR on the aircraft were working properly.

It's hell when you find out half way into a mission, that a critical piece of equipment is not working.
it's better to test a piece of equipment early, and not need it,than to find out it isn't working just when you need it.

San Francisco is the comm center for most of North America.
They operate several regional XMTR Channels covering ALL on the USA.
129.45 is a regional ARINC channel. for the Midwest.

The VHF ground transmitter was probably in STL, the HF ground XMTR was probably at at Cedar Rapids,Iowa near the COTHEN installation that Rockwell Industries operates.

 

[radio10-8]

Thanks for sharing this information. I found it very interesting. I am researching more on AIRINC always looking for something new to listen to.

 

[kma371]

This is the history of that particular flight: https://flightaware.com/live/flight/SCX504/history/20160403/2305Z/KDFW/KMSP

It has just come from Cancun to Dallas and you likely heard it from Dallas to Minneapolis.

They may have just been testing the radio like the other said.

Just some useless trivia, ARINC/Rockwell's "San Francisco" comm center is located near me in Livermore, CA. Their HF Pacifc Ocean transmitters are located in Dixon, CA