Avionics Bending: Audio Panel Integration for the L-1011 Trainer

Tim Joransen and myself discussed how to do realistic audio panel integration for the simulator. So, to use a Virtual Air Traffic Control System (in our case VatSIM) we are currently thinking about using XSquawkbox.

To make the cockpit experience as realistic as possible from an audio perspective we need to have a number of discrete audio channels that can be fed into and received from the 4 audio panels in the cockpit. What and where are the four audio panels?

1. Captain's Audio Selector Panel on the aft center console
2. First Officer's Audio Selector Panel on the aft center console
3. Second Officer's Audio Selector Panel on the lower Flight Engineer's Console
4. Observer Audio Selector Panel to the left of the observer's seat

L-1011 Audio Selector Panel Locations - From Delta Pilot's Reference

Most audio panels made by Gables Engineering have a very similar pin configuration. And allow for a number of external components to be connected. For the L-1011 project, here are the external elements that connect to each audio selector panel:

• Headset (All Stations)
• Boom Microphone (part of the headset) (All Stations)
• Oxygen Mask Microphone  (All Stations)
• Hand Microphone (Captain, F/O and S/O only)
• Overhead Speaker (Captain and F/O only)
• Yoke R/T and INT Switch (Captain and F/O Only)

Here are the different audio channels that need to be fed to the Audio Select Panel to make the simulation as realistic as possible:

1. VHF COM 1 Audio (xsquawkbox)
2. VHF COM 2 Audio (xsquawkbox)
3. VHF COM 3 Audio (xsquawkbox)
4. HF COM 1 Audio (tbd)
5. HF COM 2 Audio (tbd)
6. VOR 1 Audio (xplane via plugin)
7. VOR 2 Audio (xplane via plugin)
8. ADF 1 Audio (xplane via plugin)
9. ADF 2 Audio (xplane via plugin)
10. Marker Beacon (xplane via plugin)
11. Ground Proximity Warning (xplane via plugin) 
12. Interphone (within the simulator)

The audio panel also routes the microphones for each of the audio stations to the respective channels. For the simulator here is the proposed mapping:

1. VHF COM 1 Microphone (to xsquawkbox)
2. VHF COM 2 Microphone (to xsquawkbox)
3. VHF COM 3 Microphone (to xsquawkbox)
4. HF COM 1 Audio (tbd)
5. HF COM 2 Audio (tbd)
6. Voice Recorder Output (tbd)
7. Interphone (within the simulator)

Of course there is still the Passenger Address (PA) system that would be, of course, part of the L-1011 however, for the purpose of building the simulator we will not worry too much about the PA system. We will not integrate the PA into the audio panel, however, the L-1011 has a Passenger Address panel on the overhead panel and we might consider connecting that. 

L-1011 Trainer Installation: Telex Airman 750 Headsets

Telex Airman 750 Headset

No serious cockpit project can go without authentic headsets. The Telex Airman 750 headset has been a standard item in commercial cockpits for a very long time. The Airman 750 is sound optimized for

radio communication and it has 400Hz hum reduction built right into the headset.

So, to add to the realism of our Lockheed L-1011 cockpit we received a donation of three Airman 750 headsets. The headsets had been heavily used before and most of the foam had done what most old foam does ... it had fallen apart. However, since the Airman 750 is still a headset that is going very strong ... finding the replacement parts was no problem at all. I can't wait to get them into the cockpit and connected to our audio panels.

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Avionics Bending: VHF/HF COM Radio Integration with X-Plane (Part 4)

Each crew member has three different ways of sending microphone input to the audio system.

1. There is a microphone attached to the headset worn by each crew member. 
2. A hand microphone is provided for the Pilot and First officer, and,
3. A microphone is installed in the oxygen mask

Each microphone is routed to the respective radio via the Mic Select switch on the audio panel. A radio will transmit when Push To Talk (PTT) switch is pressed. The pilot an First officer have 3 ways of keying the PTT:

1. The pilot and first officer yoke have a Push To Talk (PPT) switch on each yoke. The following two images show a typical Boeing 737 yoke with the PPT switch located on the forward facing side of the left hand grip.

B737 Yoke and PTT

B737 Yoke and PTT

2. Each crew station in the cockpit is also equipped with a hand microphone. The image below shows a typical Telex hand microphone as used on the L-1011 and many other aircraft type. The push button on the top of the hand mike has the same function as the PPT switch sown in example 1.

Hand Microphone PTT Switch 

3. The microphone can also be keyed with a small switch located directly on the audio selector panel. In most cases, this PPT switch would be used in conjunction with the Oxygen Mask microphone.

Audio Selector Panel PTT

For the simulator project, all three ways of keying the microphone results in a "transmit" setting on the flight simulator. 

Avionics Bending: VHF/HF COM Radio Integration with X-Plane (Part 2)

Overview

There are quite a large number of audio sources that pilots use during flight and on the ground. Not all audio sources are really meaningful in a simulator cockpit, however, I will attempt to create and implement as many as possible. So here are the radio sources, as well as other sources that produce audible signals, most commonly found on large transport aircraft:

1. Very High Frequency (VHF) radios are mostly used for communication and navigation. VHF COM is used both in the air and on the ground to talk to controllers as well as listening to weather services like AWOS. VHF NAV is used for navigation, however, also carries audible signals in the form of Morse Code (for VOR and ILS identification and sometimes DME) and/or voice signals for other automated signals. 
2. High Frequency (HF) is used for company communication from the ground to aircraft and the other way around. HF really has not much of use in a simulator, however, I will still cover it as part of this effort because maybe there is something fun that can be done with it (maybe SELCAL integration).
3. Automatic Direction Finder (ADF) uses a band that is in many cases also used by AM radio broadcasts. The NAV aids are also known as Beacons and also have Morse Code for Beacon identification. 
4. Marker Beacons are part of the Instrument Landing System (ILS) and typically consist of 3 radio Beacons called; Outer-, Middle- and Inner-Marker. Each of them has a different frequency that is represented in the cockpit by goth a visual queue (a blue, orange and white light) as well as an audible signal in the form of 3 different tones. 
5. Passenger Address (PA) System allows the cockpit and cabin crews to make those lovely announcements about keeping your seat belts on until at the gate and look out the left window to see the Grand Canyon. 

The most interesting sources to implement with the simulator are the VHF, ADF, Marker and PA sources. VHF COM is most frequently by using either a synthetic ATC system or by connecting to a simulator service like VATSIM run by real people who act as flight controllers. My plan is to implement with VATSIM for the VHF COM radios. 

Technical Implementation

One of the core issues is that most flight simulators output a stereo-mix of audio, however, for the Audio Panel I need discrete output from each simulated audio source. Some of the audio output will need to be created from scratch, here are some thoughts on the signals:

• VHF Voice - use the VATSIM output.
• VHF NAV - generate Morse code based on the NAVAID name
• ADF - generate Morse code and mix in some type of radio or other signal
• AWOS - use text to speech generator 
• Marker - use sound generator to create marker beacon signal

All in all the integration for each of the 3 radio head/audio selector panel combinations will look as follows:

Original Flight Hardware: Passenger Address (PA)

The Passenger Address panel can be found on the pilot overhead panel. It is used to monitor PA announcements in the cabin area of the Lockheed L-1011. The panel that I have has a volume button for the PA monitor, two zone selectors labeled "FIRST CLASS" and "COACH AREA" and a dB meter.



The overhead panel drawing below shows the Passenger Address panel without the zone selectors and the volume indicator. It appears that the panel below was actually the more frequently used on the Lockheed L-1011.



Panel Location