Real World Audio Control Panel Functionality

[John Golin]

Thanks JHW... much appreciated.

[farrokh747]

hello!

Trying to get my head around the external audio switching hardware to make this work...

JG, with PSX ACP functional, I guess the trick would be to control what audio goes to which headset/spkr and from which mic given the various RMP, ACP button etc states...?

Looking at this earlier discussion http://aerowinx.com/forum/topic.php?id=495
one can wire the ACP's as "dumb panels" as PSX will have all the logic to control the panel - easy enough, and the switches and led's will work accordingly - however,  the phisical mic/headset and speaker systems in our cockpits will be 'outside' of PSX, but will need to be controlled by some switching in order for the system to work realistically - this throws up a complex (to me!) matrix of and/or logic, and here's where i'm stuck.

@Jeroen from above thread::
In order to drive backend systems such as actual audio amplifiers/distributors and online flying voice output, your systems need to read the PSX states such as the antenna.

any idea what would a system like this be? a series or micro relays?

@JHW,
The Audio Management Unit combines all the selected receiver audio and sends it all to your headset

So taking this example, can one hardware-simulate the AMU somewhat?

each 'circuit' (VHF1 rec, VHF2 transmit, Marker, VOR ident, Capt Mic, FO Head set, Capt Hand Mic, etc, etc) can be switched to one or more other circuits, depending on state....

Additionally, does anyone know of a scenario in online flying where HF and SAT are used?

Thanks in advance!

FC

[farrokh747]

OK I see from the screenshot here: http://aerowinx.com/forum/topic.php?id=687

that the P1, P2 and OBS headsets are assignable to separate instances of PSX - and thus to separate audio cards - Great! - that leaves the MICS and mixing with online atc returns...

Not sure what Interphone speaker L & R, and PNF Unamplified are...

fc

[John H Watson]

@JHW,
The Audio Management Unit combines all the selected receiver audio and sends it all to your headset

And to the speaker (if selected on).

That's the theory. At the moment, I can't think of any exceptions*  :mrgreen:

..one can wire the ACP's as "dumb panels"

The ACP's are dumb panels in reality, too  

*The VHF Direct Switch on the overhead panel allows the Captain to bypass the Audio Management Unit (if it fails). Receiver audio/Sidetone will only be heard at the Captain's headset. I don't think it will be heard at any other station or at his speaker.

Rgds
JHW

[John Golin]

FC:

Your analysis from that thread is what I am basing my assumptions on for the time being... I'm hoping software can fill any void to make it easier (and cheaper) for everyone...  getting the logic sorted is the hard bit, with software you can do ANYTHING

JHW:

Thanks - so to confirm - when Direct is used, the other two ACPs do not hear any VHFL comms?  

Cheers!

[John Golin]

...and a couple of other things have come up...

Interphone On / Off
I'm reading from 5.10.10 in a 744 FCOM where it talks about the Service Interphone and Cabin / Cargo Interphone switches on the aft overhead.  Simplifying somewhat, do I understand correctly:

SERV INT - OFF => flight crew don't hear ground crew, ground crew don't hear flight crew regardless of ACP settings.

CARGO / CABIN - does this do the same thing for the CAB lines of the ACPs?


PTT Behaviour

If a crew member is transmitting on a radio, are other crew members blocked from transmitting on that radio? (ie pressing PTT, nothing happens?)

And conversely, I assume there is no restriction on crew transmitting on different radios at the same time...

SAT
I gather from the same document that SAT calls (apart from the Automatic DataLink type) are managed via the CDU alone? i.e. If I want to call company on the SAT voice circuit, I do something in the CDU...

What about incoming? I gather company 'begin' a SAT call, triggering the CALL light ?


Thanks!

John

[John H Watson]

SERV INT - OFF => flight crew don't hear ground crew, ground crew don't hear flight crew regardless of ACP settings.

It depends on where the ground crew plug in their boomset (headset/mic).
At the nosewheel, there are two jacks. One is labelled Flight Interphone, the other Service Interphone. The Flight Interphone jack allows comms without the Service Interphone Switch ON. There is also a jack in the Main Equipment Centre which is said to be tied into the Flight Interphone also. However, there are variations to this. Some ground personnel have tried to communicate with the pilots from the nosewheel and then realised that their headsets were faulty (damaged cord, etc). In this situation, rather than call for a new headset, they have climbed into the Main Equipment Centre to use the headset & mic there, but have been unable to get a response from the flight deck. Some diagrams show that the switch is required for this MEC station. So, 744 pilots(!!!), if you can't get a response from the ground, look for hand signals or turn on the Service Interphone

CARGO / CABIN - does this do the same thing for the CAB lines of the ACPs?

I don't have much information on this, but it is said to operate in the same way as the Service Interphone. Comms can even be established between the cargo system and the service system by using the Service Interphone switch at the same time. According to the manuals, when a call is initiated from the cargo to the flight deck, the cargo call light illuminates on the pedestal PCP (freighter version). The light remains illuminated until the cargo loader pushes his/her PTT. The call light does not come on in the cockpit for pilot to cargo calls.
I have no information on the Combi. I'm not sure if it integrates the cabin interphone and cargo system or if it is more like the service interphone (Calling chime/light system unknown). Any combi guys out there?
 

If a crew member is transmitting on a radio, are other crew members blocked from transmitting on that radio? (ie pressing PTT, nothing happens?)

I'm not aware of any limitations on the number of people trying to talk at the same time. e.g. When using the nosewheel interphone to speak to the flight deck, for example, I can still hear the guy upstairs speak if I key my microphone at the same time.

And conversely, I assume there is no restriction on crew transmitting on different radios at the same time...

Only the Left and Right HF system has an interlock to prevent you transmitting on Left and Right at the same time.

SAT
I gather from the same document that SAT calls (apart from the Automatic DataLink type) are managed via the CDU alone? i.e. If I want to call company on the SAT voice circuit, I do something in the CDU...

What about incoming? I gather company 'begin' a SAT call, triggering the CALL light ?

I should let the pilots answer this as they would be more familiar with the operational side, but, basically, the CDU allows the selection of the phone number to be called. This information is passed on to the SATCOM system which handles the channel assignment (Some systems have 6 voice channels for pilot and passenger use) and outgoing/incoming call signals. When the ground responds the SAT "CALL" lights will illuminate on the Audio Control Panels and the pilot would push the appropriate SAT L/R mic button on the Audio Control Panel and then key their microphone to begin conversation (There is nothing to stop the pilots pushing a SAT L or R button before selecting a number via the CDU, however).
When the ground calls the aircraft, the CALL lights(?) illuminate. The pilot selects the appropriate SAT button and speaks into the microphone. No other selections are necessary for incoming calls.

Rgds
JHW

[John Golin]

I have managed to come up with another two three more questions!

When CAPT AUDIO SYSTEM is set to VHF-L DIRECT (on the aft overhead), I understand this effectively bypasses the ACP and locks the CPT Headset to VHF-L at 100% volume.

- I assume therefore, as with any other line, INT not longer works (i.e. if CAPT xmits using INT PTT nothing happens)
- Does  the R/T PTT on the ACP still work?
- I also assume VHF-L direct takes precedence over OBS AUDIO SYSTEM override by CAPT... ie. if both are selected, VHF-L 'wins'?

Cheers!