Saturday, November 9, 2019

Vibration damage in avionics is a thing (who knew?)

The Airball probe stopped working a few days ago while I was taxiing N291DR along the gopher-hole-pitted grass runway at the Monterey Bay Academy airport (CA66).

If you don't know this, the Monterey Bay Academy is a Seventh Day Adventist boarding high school in our region. They have an airport (of course! which self-respecting boarding high school doesn't?). And they have for years very generously made it available to the flying community, so long as you respect their rules -- mainly, refraining from landing during the Sabbath. They are awesome folks.

I have been working up to landing at their strip, which is sort of a "bush flying kindergarten". A few days ago, accompanied by my wife (and Airball Product Marketing Manager) Melissa Blum, I landed there as PIC for the first time ever!

Airball worked fine, until we did the long back-taxi down the bumpy runway. Then it stopped sending data. It's been a few days since I had the chance to pull it off the airplane and debug, but now I think I know what happened.

In this video, you will see that merely by wiggling the Pro Micro Arduino daughterboard, I can get it to turn off and on. So basically, the power supply solder connections or circuit board traces were mechanically damaged by the bumpy taxi!!

I found this out when I was poking around the circuit with my test probes and just happened to notice that the act of poking with the probes itself got the thing to light up and start flickering and sending data. Here is the video:

So the realization du jour is: Vibration in avionics is a thing.

Clearly I need to redesign my probe somewhat to add rubber vibration isolators to the board mount. This is a bit of a pain in the neck as I had hoped to be done with futzing with the probe mechanical design, to be perfectly honest. But I have to do what I have to do.

I hope I can manage to get some sort of isolation mount for the rear of the board. As you can see in the video, that area is already pretty "busy" and is not designed with any sort of simple mounting holes. 

1 comment :

  1. You also need to redesign your probe to better resist vibration damage. For a start, constrain the power leads so there's less wiggling mass hanging off the problematic solder joints.