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Author Topic: Emergency voice communication on NDB frequency  (Read 482 times)

Hardy Heinlin

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Emergency voice communication on NDB frequency
« on: Sat, 10 Apr 2021 07:13 »
Good morning,

in case of a VHF failure, ATC may use a certain NDB frequency to talk to the pilots. They will hear the instructions from their onboard ADF.

Worldwide nav databases indicate whether an NDB supports two-way voice. No NDB in the USA supports two-way voice, but there are many other NDBs in the world that seem to support it. Has any pilot on this forum ever talked on an NDB frequency? I wouldn't even know how to do it. Are there any special avionics that provide such a feature for emergencies?


Regards,

|-|ardy


P.S.:

It may be a database issue. When I compare the FAA's USA section with Navblue's USA section, Navblue has set the "no-two-way-voice" mark on just a few USA NDBs, while the FAA has set it on all USA NDBs.
« Last edit: Sat, 10 Apr 2021 07:26 by Hardy Heinlin »

Will

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Re: Emergency voice communication on NDB frequency
« Reply #1 on: Sat, 10 Apr 2021 13:40 »
The NDB frequencies overlap with commercial AM radio frequencies, which broadcast voice literally all the time. So the world is fully stocked with both transmitters and receivers that operate in the NDB range. Whether any of those transmitters are carried by aircraft, I don't know.
Will /Chicago /USA

DougSnow

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Re: Emergency voice communication on NDB frequency
« Reply #2 on: Sun, 11 Apr 2021 12:22 »
When I dispatched at America West/PHX, I commuted out of ORD weekly.  On the way back home, I'd sometimes fly with an AWE line holder who lived in Rolling Meadows, and once we leveled off in cruise (A320 equipment) he'd dial up 890 AM WLS, and as we passed East of the Rocky Mountains, the ADF would point its way home. 

Hardy Heinlin

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Re: Emergency voice communication on NDB frequency
« Reply #3 on: Sun, 11 Apr 2021 13:18 »
Will and Doug, that's clear. But -- vice versa -- how would you, on the flight deck, talk over your ADF to ATC?

The HF COM range starts at 2.0 kHz.

The NDB range ends at 1.7 kHz.

Or am I misunderstanding the term "two-way voice"?

Jeroen Hoppenbrouwers

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Re: Emergency voice communication on NDB frequency
« Reply #4 on: Sun, 11 Apr 2021 16:23 »
The only way I can imagine is if there is explicit equipment installed that can transmit on those unusual frequencies. In this case, a HF set that can actually reach all the way down to the NDB band. It may even require an extra set of antennas.  As airlines typically shy away from absolutely everything that is not legally mandated, I doubt many airliners have this capability.

I also had never heard of two-way NDB capability and believe it is one of those older systems that isn't really in use any more but pulling it offline is just a step too far at this moment.

Hoppie

simonijs

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Re: Emergency voice communication on NDB frequency
« Reply #5 on: Sun, 11 Apr 2021 18:31 »
ICAO Annex 10 Aeronautical Telecommunications (VOL II Part II Voice Communication Systems, dated 2001) has zero information on communications through NDBs. The only reference to two-way voice communication is for HF and VHF. All other reference to NDBs...: only as a Radio Navigation Aid.

In VOL V Aeronautical Radio Frequency Spectrum Utilization (2001), there is a note under 3.2 NDB Frequency management: "Attention is drawn to the fact that some portions of the bands available for aeronautical beacons are shared with other services".

This same VOL V contains a VHF frequency allotment table, which may be handy for another thread on this forum. If you like, I can take a screenshot and send it by e-mail.

Regards,
S.

Hardy Heinlin

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Re: Emergency voice communication on NDB frequency
« Reply #6 on: Sun, 11 Apr 2021 21:13 »
Thanks. Well, I guess we can ignore this two-way stuff then ...


Regards,

|-|ardy

Jeroen Hoppenbrouwers

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Re: Emergency voice communication on NDB frequency
« Reply #7 on: Sun, 11 Apr 2021 21:25 »
You can always plant an Easter egg.

(tunes NDB)

daa di    daa di di     daa di di di

daa di    daa di di     daa di di di

<crackle> <crackle> Hello? Can anybody hear me?

daa di    daa di di     daa di di di

daa di    daa di di     daa di di di


Hardy Heinlin

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Re: Emergency voice communication on NDB frequency
« Reply #8 on: Sun, 11 Apr 2021 21:39 »
... with a Dutch accent ...

Will

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Re: Emergency voice communication on NDB frequency
« Reply #9 on: Mon, 12 Apr 2021 02:40 »
Again, I'm not an expert here, just thinking out loud... I would think that the 707 and the 747-100 would have all the necessary radio telephony equipment for the jet age. If transmitting over NDB frequencies was needed in some part of the world after 1960, then some 707 or 747 operator would have had that piece of equipment installed. Finding out would require a bit of research into what was available in the cockpits of those two models over the years, but I bet that therein would lie your answer.

Prior to the jet age? If some DC-3s transmitted over NDB frequencies in 1940? Maybe more plausible, but perhaps also more difficult to prove (and perhaps less relevant to a simulation of the 747-400).
« Last edit: Mon, 12 Apr 2021 02:59 by Will »
Will /Chicago /USA

jcomm

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Re: Emergency voice communication on NDB frequency
« Reply #10 on: Mon, 12 Apr 2021 08:58 »
Found mention to:

- Voice transmissions are made on radio beacons unless the letter "W" (without voice) is included in the class designator (HW)

in this url: https://www.cfinotebook.net/notebook/avionics-and-instruments/non-directional-radio-beacon

Hardy Heinlin

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Re: Emergency voice communication on NDB frequency
« Reply #11 on: Mon, 12 Apr 2021 09:13 »
In ARINC 424, in general, the letter W indicates "No voice on frequency". But in ARINC 424-19, for the letter W, they added the explanation "The frequency of this Navaid is not used to support two-way communication between a ground station and aircraft". -- That's the confusing part.

But, of course, "no voice at all" implies "no two-way".

The quoted "HW" seems to be a random quote. H just means "High altitude". The code can be:

H  HW
H    W
H  MW
H  LW

Anyway, the whole context of the second letter refers to voice:

A = Automated weather reports
B = Non-automated weather reports
W = No voice (explanation: no two-way voice)
Blank = Voice on frequency (explanation: used to support two-way voice)

They should have used the word "may" in their supplementary explanations.
« Last edit: Mon, 12 Apr 2021 09:42 by Hardy Heinlin »

Will

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Re: Emergency voice communication on NDB frequency
« Reply #12 on: Tue, 13 Apr 2021 03:04 »
The "W" in the United States means "no voice," but the Airman's Information Manual only says that "W" means the station can't transmit voice. VORs will occasionally transmit recorded flight information alerts or they'll have a recorded voice identifier. With the "W," all you get is the Morse code. You know this already.

I couldn't find anything that talks about two-way voice communication over navaids. I'm wondering if that was left over from a previous technological era.
« Last edit: Tue, 13 Apr 2021 03:50 by Will »
Will /Chicago /USA