I was doing my preflight inspection of a Piper Dakota one fine winter morning. There was still a bit of snow on the ground, but it was melting. As I lifted the fuel cap on the left wing, I heard and felt a slight puff of air. Though nothing in my flight training mentioned anything about this, I got very suspicious. This fuel tank is not supposed to have a vacuum or be pressurized.
Earlier that week I had been reading an aviation safety newsletter that described an unusual case of an engine stoppage in mid-air. It turned out that mud dauber wasps had built a nest inside the breather tube for the fuel tank. Though this was not the season where one might expect such critters, I walked to a nearby tree, and picked a twig off of it. I whittled down the twig to the size of a toothpick so that I could see if the straw-sized breather tube was blocked.
Holding my fuel sample cup underneath the breather tube, I poked around and was rewarded with a bit of ice slush and a small gush of entrapped fuel. I am certain that had I taken off with that slush in the breather tube, it probably would have frozen solid (the freezing altitude was less than 1,000 feet above ground level), and it would have eventually caused an engine stoppage in mid-air. Since that day, the breather tube is now part of my pre-flight inspection routine.
This entry was submitted by Jake Brodsky and edited by Rob Spiegel.
Jake Brodsky is a senior staff engineer, registered in the state of Maryland. He built a career at the Washington Suburban Sanitary Commission for more than 24 years.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.