ARinc 429 reader for troubleshooting

Hi

Did anyone work with ARINC 429 readers for troubleshooting ?? i am new to avionics .like to learn about ARINC readers 429 trouble shooting.i know the theory side.but don't know how to make it for practical use.. any help appreciated..thanks in advance.

I have only used a 429 reader a couple of times over the last 20 years. It was interesting to actually "see" the data coming across a data bus.

You could possibly use one to simulate data into a computer, but that would be more on the engineering level.

The nice thing about digital data is that the boxes "know" what signals they should be receiving. Not only that,but what tolerance threshold that data should fall within. Any deviation from the norm will be recorded as a fault. All newer avionics platforms allow for retrieval of those faults.

The computers are actually acting like the data buss analyzers because their "job" relies on proper input data. Flight Fault History and Current Faults are a HUGE troubleshooting tool. All newer aircraft have this data available for use, it's just figuring out how to get it to "talk" to you. Newer Boeing aircraft have it readily available via CFDS. I've found A300's a little more difficult to extract faults.

It's all there. Sometimes some serious "digging" is needed to get it out.

i think what we study theoratically, is different from what we do practicallyy..and i think we need some good training from some manufacture of these arinc readers..even some videos with practical examples will be a great help..

I just found this online.

thanx markk!!!

I recently worked on a 737-400 with a IRU data bus output failure.

In this case, there were about 10 user systems including Auto-Pilot, Auto-Throttles, TCAS, Ground Proximity, Weather Radar, and others.

The issue that I was seeing was a grounded "blue" (or low) data bus wire. It is somewhat confusing, but "low" does not mean ground when dealing with data bus signal wires,

With either the red (high) or blue wire grounded, the data from the transmitting unit will not be seen by the users. I have also seen in the past where a user system component will have a shorted or bad 429 receiver circuit which takes the whole bus down.

With this particular aircraft's problem, I pulled or unplugged every user component and the IRU itself. I wanted to make sure that the ground I was seeing was not being read through one of the boxes. The ground was still present with all boxes removed. Due to weather conditions and allotted time, I was not able to proceed further with the troubleshooting.

The actual problem turned out to be a bent pin on a rack connector that shorted the blue signal wire to shield ground. I was not present for the actual find. The technicians working on the problem had to remove rack panels and open up quite a few areas to find this particular plug.




As a note: With everything installed on a working system, I read higher than 2 Meg-ohms to ground on both the blue and red wires.

I can relate ARINC to CAN bus networking used in cars. There are two resistors 120 OHMs each, in parallel, in the network, and if one goes bad you will loose the High/Low signals. If you read 120 OHMs on the network, one resistor is bad. This should be similar to ARINC.

Live 429 data bus from the #2 (right) Air Data Computer. This particular output was picked up from the Thrust Management Computer rack plug.
  
  

Image of paused data from video above....