Loss of com: ATC calling on 121.5...

[LazyFrog]

Good day,

Question to our fellows AT controllers. On every flights, i can hear ATC calling on 121.5 flights they have lost contact with: why not using Selcal to trigger cockpit alarm with those flights reporting this equipment in the FPL?

Regards.

[ron83]

Very simple,because not all centres have selcal equipment.

[The Many Tentacles]

At Swanwick we have no facility for making a Selcal so that sort of answers your question.

Best we can do is get D&D to try 121.5 or speak to Shannon and get them to try for us

[AlphaTangoCharlie]

It's standard practice in Shannon! We have to do it numerous times a day, mostly when aircraft are a bit slow reporting at 15W.

If we are calling on 121.5, a lot of the time it can be time critical. We may need the aircraft on frequency for a level change or there may be conflicting traffic in the area.

Getting an aircraft selcald requires a lng chain...phone call to ballygireen, pass the message to the HF operator, look up the selcall digits, send the selcal, wait for the aircraft to respond, then tell them to call Shannon on 132.15.

It is easier to select 121.5 on our compads and say "ABC123, if you read call Shannon on 132.15"

We also have the option of a satphone in the case or PLOC, but it is rarely used.

[LazyFrog]

@ ron83: disappointing... it's way from being the most expensive of the ACC equipments?

@ The Many Tentacles: it's surprising... meanwhile, within europe, i never heard any Selcal tones on 121.5 or any other VHF frequencies.

[LazyFrog]

@ AlphaTangoCharlie: "...Getting an aircraft selcald requires a lng chain...phone call to ballygireen, pass the message to the HF operator, look up the selcall digits, send the selcal, wait for the aircraft to respond, then tell them to call Shannon on 132.15..."

In that case you mean asking aeradio operator to send the Selcal via HF, right?

My initial post is about the loss com as the result of cockpit audio panel volume set to or near to zero and/or wrong frequency set on VHF 1. The worth case would be of course a wrong set of frequencies on both VHF (VHF 2 set to ATIS, VOLMET, OPS...). But let's consider the case with audio panel volume set to zero: ATC would get some benefit of this old technology using-it on 121.5... and the code being part of the FPL of equipped aircrafts (-REG/XXXXX SEL/ABCD...), it shouldn't be a big workload to get the selcal digits?

[fisbangwollop]

Selcal only works on HF.....never heard of any VHF sets being equipped with it....no need as once VHF is squelched you can sit there and be happy hearing no noise until the squelch is lifted by a transmission. :cool: Try listening to the RF noise on HF during a 7 hour flight and you would be driven to drink..!!! Hence the need for Selcal on HF.

http://www.youtube.com/watch?v=5ezransH9jI

[mutt]

Not so Fisbangwallop....

SELCAL operates on the high frequency (HF) or very high frequency (VHF) radio frequency bands used for aircraft communications. Pressing our selcal test switch activates HF1 HF2 VHF1 VHF2 VHF3 call indicators.

Mutt

[LazyFrog]

@ fisbangwollop: "Selcal only works on HF..." that's not true, onboard decoder works as well with VHF (mutt is right).

"...Try listening to the RF noise on HF during a 7 hour flight and you would be driven to drink..!!!..." Yes, onboard HF don't have squelch but it seems to be an aviation industry standard only, not a standard for SSB operation: "voice squelch" is intensively used on the marine radios and others...

[fisbangwollop]

Thanks for that Mutt....you never stop learning. :cool: