Civilian aircraft on HF-GCS, 11175 kHz, USB

[Token]

Heard something on the HF-GCS network today that I don't think I have heard before. Two different regularly scheduled United Airlines flight, at different times, requested a radio check on 11175 kHz, and both times got a response from West Coast.

At about 2218 UTC on April 15, 2023, United 1948 requested a radio check from Mainsail on 11175 kHz. "Mainsail, Mainsail, United 1948 radio check on 11175 kHz". This was sent twice, two different transmissions. The response after the second transmission was "Last caller, last caller, this is West Coast, West Coast, please say again last, over". From United 1948 "I've got you loud and clear, I was just trying a radio check, I might try one more frequency also". From West Coast "Lima Charlie on triple one seven five, over". From United 1948 "thank you for that".

A few seconds later, from United 1948, "West Coast, West Coast, United Nineteen-Fortyeight on triple one seventy five". Form West Coast "Last caller, last caller, this is West Coast, have you Lima Charlie, over". From United 1948 "United 1948 has you Lima Charlie, thank you very much for the checks".

Checking flight schedules, at that time United 1948 was en route and a couple of hours out from Cancun to San Francisco.

At about 0042 UTC on April 16, 2023, about 2 and a half hours later, United 519 requested a radio check. This time I really could not make out much of United 519's traffic, but I heard all of the HF-GCS (West Coast) response. From West Coast "Last caller, last caller, this is West Coast, please say again last, over". From West Coast "United 519 this is West Coast, I have you Lima Charlie, over". A bit later, from West Coast "Last caller, last caller, I have you Lima Charlie, over". From West Coast "Untied 519 this is West Coast, I have you Lima Charlie, over".

Again checking the flight schedules, at that time United 519 was en route from Washington and a couple of hours out of San Francisco.

T!

 

[airwolfbell222]

I heard it too, I was surprised that 2 different UAL flts came up today.

 

[WB5UOM]

Civil Reserve Air Fleet

A unique and significant part of the nation's air mobility resources is the Civil Reserve Air Fleet, or CRAF. Selected aircraft from U.S. airlines, contractually committed to CRAF, augment Department

www.af.mil

Now no one knows- but they could possibly have been check flights demonstrating proper hf comms to West Coast "Hilda West AMC"

its been a long time since Ive heard that.

 

[letarotor]

It's been a long time too since I've heard a civil airline on one of the old GHFS frequencies. I believe I heard American ### at least on two different instances in past years. I wasn't 100% sure at the time, and we didn't have ADSB and other means of really checking, that it was a commercial aircraft. But it definitely sounded like one and I remember one other time that I was more sure that that's what it was than the other time.

I did not know about the CRAF deal either. Does this mean that specific aircraft used by airlines have the 11175 capability to transmit in them or would all of them?

Brian
COMMSCAN

 

[FrensicPic]

UAL519 on 11175 surprised me too!

 

[Token]

I did not know about the CRAF deal either. Does this mean that specific aircraft used by airlines have the 11175 capability to transmit in them or would all of them?

Pretty much all airliners (that might travel internationally or over water) have the capability to dial up 11175 kHz. Their radios can tune to that frequency. But it is not something I think I have heard before. Then again, I do not monitor HF-GCS often, so maybe I just never heard it.

As for CRAF, I was aware of it, but hadent really thought about it for years. I know that the US government, in the past, subsidized some aircraft leases and purchases by airlines, and intentionally used civilian charters even when it had the airlift capacity itself, with the agreement being that in case of need the US mil could claim first priority to transport whatever was needed. For example, during the Cold War, in the event of a Warsaw attack in Europe, Operation Reforger would rely on civilian aircraft (in addition to military aircraft) to transport the required troops to mate with their pre-positioned assets. The aircraft would take civilian dependents and non-combatants out of the theater on the return legs.

T!

 

[bearcatrp]

Currently listening to a message on 11175 USB. Are the civilian aircraft on this freq only at night?

 

[bearcatrp]

Am hearing multiple voices right now. Never heard some of this before.

 

[FrensicPic]

A lot of activity (Deck Boat) on 11175/8992/15016 today. (2100Z)

 

[Token]

Currently listening to a message on 11175 USB. Are the civilian aircraft on this freq only at night?

Normally they are not on that frequency at all, that is why this is potentially noteworthy. However, when they were active on the freq (2218 UTC and 0045 UTC) it was not night time, it was still daylight where they were and were the responding node (West Coast) was.

T!

 

[Token]

Am hearing multiple voices right now. Never heard some of this before.

A lot of activity (Deck Boat) on 11175/8992/15016 today. (2100Z)

There is a lot of activity this weekend, and for the past several days, probably because of a planned exercise, Global Thunder. The level of activity is consistent with such a large scale event.

"Deck Boat" is the daily callsign that started in use at 0000 UTC today and will continue until it is replaced at 0000 UTC tomorrow.

T!

 

[Hudson45]

I heard it too, I was surprised that 2 different UAL flts came up today.

That's interesting! It's possible to hear multiple United Airlines flights on the same day due to air traffic and radio propagation. Enjoy monitoring, and feel free to share any more exciting findings!.
g

 

[Token]

That's interesting! It's possible to hear multiple United Airlines flights on the same day due to air traffic and radio propagation. Enjoy monitoring, and feel free to share any more exciting findings!.
g

The surprising part is not that two UAL flights can be heard, but rather the frequency they were heard on. The frequency in question is normally associated with the US Air Force or other US military services. This is not, generally, a frequency one would expect to hear civilian airliners on at all. And the fact that two different civilian airliners were heard on that frequency within a few hours is extremely unusual.

T!

 

[GadgetGeek]

Very strange indeed.

 

[db_gain]

I've heard it over the decades, and a lot of commercial jet jockeys are former USAF and USN pilots and recall the old freqs for hfgcs.
I assume this is common courtesy for hfgcs to acknowledge commercial flights as an aid to flight safety.

 

[fires999]

Morning from a dull UK,
Being on Base here (USAF Mildenhall) as expected various different USAF airframes transient through on their way to/from CONUS, or Eastbound Europe and beyond, regulars being KC-135's , C-17's & C5's.
However we have semi regular " Civvy" airlines contracted via USAF for cargo etc - I have noticed when they are on Base ready to depart they often confirm VHF frequencies, plus UHF options , bizarrely the Base is not HF equipped!!! (certainly for everyday use) so HF requests are often carried out between aircraft on the ground.
One example is Atlas Air, a regular flight from Ramstein, Mildenhall, back to Dover ? and I have often heard calling a Based Aircraft such as one of our KC-135's or MC-130's for a HF check on 11175 or one of the equivalents such as 8992 or 15015
We have a wideband receiver in Fire Dept 500hz- 3ghz , however have never personally heard civvy aircraft on Mil HF either at work or on my home set up.
Hope my input helps.
Have a god weekend,
Kevin ( Fire Dept USAF Mildenhall , UK)

 

[Token]

Heard this again this AM. 01/01/2024, about 1458 UTC United 470 attempted to call MAINSAIL on 11175 kHz USB. MAINSAIL responded with "last caller, say again" but the two never completed the contact.

Checking schedules, United 470 is in route MCO -> SFO (Orlando FL to San Fran CA), and about 20% of the way there.

T!

 

[hrspotter]

0933 EST, 1433Z - UNITED 1719 (KMIA to KIAD) just south of Brunswick, GA requests radio check on 11175 kHz from MAINSAIL. MAINSAIL replies weak and unreadable. UAL1719 has him 3 by 3.

0935 EST, 1435Z - Radio check repeated. MAINSAIL has UAL1719 weak but readable, UAL1719 replies loud and clear.

 

[markliu]

Interesting information! Thanks for sharing the frequency details. I'll have to give 11175 kHz a listen and see what comes through. Always fascinating to hear what's out there on HF!