You did what?

Staff -- Test & Measurement World, 1/1/2001

Where there’s smoke, there’s foam
When I was in the New Zealand Air Force, we needed to connect strain gauges on an A4K Skyhawk aircraft to a datalogging module. The engineering officer gave my colleague a sketch of the pin-out for the connector that showed the sensor connections. We wired up the connector and tested the logging system on the ground before packaging it in foam, boxing it up, and mounting it in the aircraft’s engine bay. The pilot started the engines and switched from “ground” to “flight” power, which caused a flash and loud bang from the engine bay. The pilot scrambled out of the plane and the safety man emptied a fire extinguisher into the engine. It turned out the engineer sketched the connections from the front, as if looking through the connector. My colleague wired the connections—correctly—looking at the connector from the back. Due to a fluke in the power source, the system worked fine while on “ground” power when we checked it. I learned to check connectors to ensure they’re wired from the proper “view.” I also learned what happens to foam when short-circuited wires pass through it.—George McNeur, Christchurch, New Zealand

Dyeing to be cool
I spent my early years teaching electronics in a high school. During a demonstration of etching printed circuit boards, I decided to heat the cold ferric chloride etchant to speed its action on the exposed copper on the PCB. Someone had left an old aluminum coffee pot in the lab many years before, so I figured I’d use it to heat the ferric chloride solution. I poured the solution into the pot, but I didn’t have to plug it in to heat the liquid. The reaction of the ferric chloride with the aluminum did that on its own! The solution got so hot it boiled out onto the desk and floor. That stuff stains tile floors and light-colored shoes a dark orange. The high-school students thought that was pretty cool.—Dennis Davis, Mankato, MN