L-1011 Trainer Installation: COM Radio Power-Up

L-1011 COM Radio Power-Up

After almost a month away from the L-1011, due to work constraints and other museum projects, it is finally time to get back into it. Today we powered up the first few elements of the aft electronics panel on located just aft of the throttle quadrant. To be exact, we powered up the 3 VHF/HF COM radio combinations.

L-1011 COM Radio Without Backlight

The radio faces operate of 3 difference 24VDC sources. The VHF1 radio receives power from the BATTERY bus, the VHF 2 radio uses the GROUND SERVICE bus and the VHF3 radio receives power from the NO.2 RADIO BUS. I have extensively blogged about these Gables Engineering devices before and you can find more info on them when you search for Gables Radio Heads here on the blog.

Below is an image of the radio face under low light conditions with back plate and display illumination.

L-1011 COM Radio With Backlight

These radio faces are ARINC 429 devices and will be controlled by ARINC 429 interface. 

Avionics Bending: Dual ADF Head

Gables Dual ADF Radio Controller

Been busy working on some additional pages for the Litton INS the last few days as well as working on the software for the SIM42911 interface we are building. However, here is a new addition to the L-1011 project - a Gables Engineering G6095A-1 ADF radio controller head.

The unit is very early digital and actually uses the standard 2 of 5 encoding on a mechanical drum and a digital decoder/display unit to show the frequency selection. Each side of the instrument is actually independent and has an independent set of controls and power source.

Once I am a bit further down the line withe work on the Litton LTN-72 INS simulation, we will do a 2 of 5 implementation together. They are fun to do and relatively easy to interface with the simulation. 

Avionics Bending: VHF/HF COM Radio Integration with X-Plane (Part 9)

Gables Radio Controller, Audio Panel and Lexicon Multi Channel Audio Interface

Up until now all the audio you heard on the previous blog postings had been live streaming ATC traffic from the Internet. While that is very cool, it is not really useful in the simulator. In the sim we want to be talking to real air traffic controllers. The good thing is that there are several large virtual flight traffic controller communities out there and VATSIM is one of them. Vatsim is a very active community, especially here around Atlanta, and you can connect to it from many different flight simulators. For this blog posting I use X-Plane as the simulator and the XSquawkbox plugin to connect to VATSIM. The video below shows a short demonstration of the end-to-end implementation of the actual flight hardware made by Gables using ARINC 429, the Laminar Research X-Plane simulator and XSquawkbox:

Avionics Bending: VHF/HF COM Radio Integration with X-Plane (Part 7)

The last two days I have been mostly working on the integration of the Gables radio head with x-plane. In particular the two VHF COM channels simulated on x-plane. Over the next few days this will then further control VATSIM and the respective VHF COM channels on VATSIM. The video above shows the integration between the original flight hardware and x-plane.

The integration architecture is pretty straight forward as you can see in the image below.

ARINC 429 to X-Plane Data Integration

The data flows from left to right in the diagram. The Gables multi function radio head outputs ARINC 429 data as described in the previous blog postings. The ARINC429 data is read by an ARINC 429 interface and then sent via UDP (Ethernet) to the computer running the simulator (in the video above that is my laptop). The system running the simulator (on the right hand side of the diagram above) also runs a device driver that receives the UDP packets, formats them for x-plane and sends them on to the TAP plugin running under X-Plane.

Next, the VATSIM integration and then we will get back to creating all the necessary audio channels for a radio experience that is close to the real thing as possible.

By the way, today I was asked by someone on the Internet if I modify the original flight hardware (such as the Gables radio heads) to work with my setup. The answer is no, all of the original flight hardware remains in its state as it was flown on the actual aircraft and is not modified at all.

Gables ATC Head: ARINC 429 Receive Tests

Taking a short break from the SFENA HSI today and tested ARINC 429 receive words with the DDC card. So far all the stuff you saw with the SFENA HSI had been ARINC 429 transmit words. The receive mode used in this example is called "mailbox" mode in which the channel on the card only remembers the last word received for a specific label. I had a Skype discussion with Edo from Italy today who is building a B767 simulator and we talked about the difference of using 2-of-5 and ARINC 429 label encoding. In 2-of-5, which is typical for ARINC 500 class devices, an ATC code or a radio frequency would be sent over 18 ore more discrete pins. Here is an example of how 2-of-5 encodes individual digits on individual pins:

2 of 5 Code used in ARINC 500 Series

The ARNC word still encodes the individual digits, but, does so in BCD format. The ARINC 429 Label also has some status information as part of a 32bit word that is being transmitted. All this data is transmitted on just two pins.

ARINC 429 Word for ATC Transponder

Typically BCD encoding uses 4 bits, however, since each position in the Transponder code only goes from 0 to 7 each digit can be encoded in 3 bits only. The video below shows a short introduction to reading the ARINC 429 label as shown above and doing a simple dump to the screen. The code is written in C.

L-1011 Avionics Bending: Gables ATC Transponder Power-On Test (Video)

The Gables ATC Transponder head that I would like to use for the L-1011 project has powered up successfully. The instrument had not been in use for several years and came out of obsolete surplus. I was uncertain if it would actually work.

The device powered up fine from a 115V 400Hz source and the head consumes roughly 43 mA.

The data-output form the head is in the ARINC 429 format. 

Avionics Bending: Gables Radio Head Operation

I thought I should add a short video on the fully connected radio head. I realized that just showing still images in the previous avionics bending blog entry didn't really show you how it actually worked.

Below is an image with my test setup using my iPad to monitor the ARINC 429 traffic coming from the Gables head. (Note: There is no direct connection between the instrument and my iPad ... the data is captured on a Linux system and the iPad just shows me the numbers via a network connection ... however, it would be really neat to have an iPad app to do ARINC 429 stream debug with).

Avionics Bending: Gables Digitial Radio Controller (ARINC 429)

I found these really cool radio heads made by Gables Engineering in Florida. The heads I have originally flew on a FEDEX MD-11, however, they could of course have also been fit into a later model L-1011. Therefore, I think they will work just fine for the project. What makes them even more interesting is that they use the ARINC 429 protocol. I have been working with ARINC quite a bit lately and so this is my first step into hooking this ARINC device up to X-Plane. Here is a more detailed description of the individual components of this Gables unit:

1. ACTIVE WINDOW - Displays the active frequency and selected radio. Displays ACARS in one of the windows for VHF-3. Displays FAIL in both windows in case of CRP failure.
   
2. TRANSFER BUTTON - Push to transfer the STBY frequency to the ACTIVE window for transmission. STBY frequencies cannot be transmitted until transferred to ACTIVE window.
3. STBY WINDOW - Displays the standby frequency and selected radio
4. FREQUENCY SELECTOR - Turn knobs to select frequency in STBY window only.
5. Push to select respective radio. Selected radio is displayed in the STBY/ACTIVE windows.
   

The first image in the blog shows the radio head selected for VHF 1. The VHF 1 information is transmitted as ARINC 429 Label 030. The data in the 32bit word is BCD. All 3 VHF radios are controlled with the same ARINC 429 label however, each VHF radio uses a different SID. The VHF1 radio is addressed with the SID set to 1.

Below is the radio selected to the VHF2 radio. Again the Label used is 030. However, the VHF 2 radio has a SID of 2.


Finally, the 3rd VHF radio (VHF 3 ) is use transmitted as Label 030 with the SID set to 3. The BCD format for the Label 030 uses bits 29-11. The digit "1" ad the beginning is not transmitted since all VHF frequencies used for communication start with a "1".


Next is a in image of what the data looks like on the computer once the ARINC 429 information has been decoded and readied to to be handed over to X-Plane.


The image above shows the 3 VHF radios on the right and the two HF radios on the left. The VHF radios are shown as VHF1, VHF2 and VHF3 from the top down. The two HF radios in the screen shot do not show the frequency because the decoder in both cases showed the second 32 it word that makes up the HF word.

The image below shows the radio set to HF1. The HF information is transmitted as ARINC 429 Label 205 for the new style HF encoding as well as the ARINC 429 label 207 for the HF status word. Label 205 transmits as two 32 bit words ... the first word holding BCD data of the first 5 digits and the 2nd word has the BCD data for the 6th digit.


Below is the radio set to HF2, again here the two HF radios are encoded using the SID of the ARINC 429 word. SID of 1 is for HF1 and a SID of 2 is for the second HF radio.


In order to make this work I used a DDC ARINC 429 adapter card. I don't have the right connector for the radio head yet, so I build a temporary cabling setup. The radio had has one TX and two RX channels. For this example, I only cabled one RX and the TX channel. The RX channels are used to synchronize multiple radio heads in the cockpit.


Unlike many other radio heads, this head actually works of 28V DC power and not the 110V 400Hz AC power that I normally use. Therefore, I hooked the entire head up to small power supply proving me with 26V DC as well as 5V DC for the instrument lighting.


The next picture shows the complete setup. The DDC ARINC card has a DB37 output, and I use a DB37 breakout board from DAQstuff.com to give me easy access to the RX and TX channels on the card.


I am not using 85Ω twinax-cable quite yet for the ARINC 429 connections, however, the distances on this test setup are so short that the channels work fine without 85Ω termination.


Gables makes some really awesome equipment and they are a super cool company to interact with!