HF Questions

[shortboarder]

Been listening to the NAT HF feeds a bit, and I have a few questions:

1 - What is the purpose of the pilots stating the fuel; and why is it a number minus another number, i.e. "fuel 26 decimal 2 minus five two"
2 - What is the purpose of the two tones at the end of a comm, and why are the tones specific for a particular plane (at least it seems that way)

[Jason]

The tones you hear are SELCAL tones, which allow aircraft to selectively monitor HF when requested by ARINC or the HF radio operator instead of continuously monitoring which is distracting and straining on the ears (lots of static and other background noise, etc.). Aircraft are assigned a 4 digit SELCAL identification (i.e. AB-CD) which the radio operator can activate on the frequency as needed.

You can get some more detailed information by googling "SELCAL"

VHF Selcal also exists, but isn't often used in the United States.

Hope this helps.

Best,
Jason

[shortboarder]

yes, thank you.  Googling HF ATC etc. gave some info, but nothing about fuel or the SELCAL tones.  Off to learn more....

[captray]

Perhaps I can help,
SelCal, Selective calling, is so you do not have to listen continuously to the staticky HF radio. It is comprised of 4 tones, designated by letters. Ours are JLCR and CRAH. These letters or tones are assigned by an association who's name  escapes me for the moment. After the tones you will hear 'N1234 answering SelCAl'. This establishes 2 way communication between the aircraft and whoever the controlling agency is. Sometimes it is for a reroute, a change of altitude or a center weather advisory.

In answer to your first question, airliners are required to report their fuel on board with their position reports. Hence; 'fuel 26 decimal 2' is 26,200 lbs of fuel. All jets measure fuel in pounds, but we purchase it in Gallons or Liters. The minus five two is the SAT, Static air temp, a negative 52 degrees Celsius. This is included with a MET report for winds aloft and turbulence. It's a PIREP out over the ocean and gives the forcasters current information to see how well the forcasts are holding up.

Hope this helps, for more info on the Atlantic Track System try this link!

http://www.nat-pco.org/nat/CurrentOpConcept.pdf

Ray

[shortboarder]

Thanks Ray! That PDF helps a lot. 

[dave]

Here is another doc which will shed a bit more light on HF NAT operations.

Enjoy.

-Dave

[shortboarder]

Thanks Dave, much appreciated!

[Rob K]

Perhaps I can help,
SelCal, Selective calling, is so you do not have to listen continuously to the staticky HF radio. It is comprised of 4 tones, designated by letters. Ours are JLCR and CRAH. These letters or tones are assigned by an association who's name  escapes me for the moment. After the tones you will hear 'N1234 answering SelCAl'. This establishes 2 way communication between the aircraft and whoever the controlling agency is. Sometimes it is for a reroute, a change of altitude or a center weather advisory.

Ray, I am interested to know what the aircraft involved are that you have fitted with JLCR and CRAH.  I run the www.selcalweb.co.uk website which has a good FAQ for all selcal related questions, plus also a searchable database (by selcal code) but although there are several entries on those codes, I don't see any correlation between any of them.  What are registrations for your two?

[captray]

That's very cool that you can search that way, JLCR belongs to N317MJ, CRAH is N995GG.
Thanks for the input!

[captray]

[

Ray, I am interested to know what the aircraft involved are that you have fitted with JLCR and CRAH.  I run the www.selcalweb.co.uk website which has a good FAQ for all selcal related questions, plus also a searchable database (by selcal code) but although there are several entries on those codes, I don't see any correlation between any of them.  What are registrations for your two?
[/quote]
I see what you mean, now that I checked the site out.
Both aircraft are G4's, they are both managed by the same company. You have GG listed with the previous operator. MJ's tail number is blocked and that is why no info comes up about the operator.

[smeuse]

Here is another doc which will shed a bit more light on HF NAT operations.

Enjoy.

-Dave

Wow, great document. I think I'm going to setup a script to tune my rx to some of the other NAT zones that dave doesn't already cover.....

[Rob K]

I see what you mean, now that I checked the site out.
Both aircraft are G4's, they are both managed by the same company. You have GG listed with the previous operator. MJ's tail number is blocked and that is why no info comes up about the operator.

Thanks.  I will remove the reference to Worldwide at the next update.   I wasn't aware of that change.

Rob