One day I was asked to take our Baby Grob up on a quick return-to-service hop. Nothing special, just once around and back down so a renter could have the bird for the afternoon. It had been a calmish morning, but by noon the air was rustling more each minute. Situation normal.
The takeoff started sleepy, then by mid-field was barely manageable. During liftoff I noticed a sudden dustup a couple hundred yards to the immediate right — keeping pace with us! What? That by itself seemed worthy of analysis, but things were changing so fast I had no time to think. It would have been wise to release right then, less than fifty feet up, but in fact I welcomed the unique experience.
After two recoveries from slack I knew more was coming, so when another devil bloomed on the right I released and rolled toward it, not 800 feet up. Just then one more sprang from below on the left. Seconds off tow I was diving through sink between two whirlies with zero altitude to spare. No problem, still essentially over the runway with no traffic, I could land whenever necessary. Yet, hazardous and challenging as the launch was, why go back down in the same chaos if I could stay up and avoid it?
A tight turn in just the right spot regained more height than I’d lost, and for half a circle it felt like the real thing. Then came that sucking feeling as my parcel of air was overpowered by a bundle of other pressures and pulled into a sharply different wind direction. Devils were forming and dissipating everywhere, moving opposite directions and changing directions so quickly, there was no keeping track of them.
I watched the towplane disappear moments before touchdown as a jack-in-the-box plume of dust exploded in its path, and sighed relief when it emerged in full climb. A minute later someone came on the Unicom to announce flight operations temporarily suspended. Good, the pilot waiting to use this bird wouldn’t be needing it right away.
For what felt like an hour I darted from one plume to the next, seldom more than a thousand feet above ground while this hyperactive interface between hot air masses swirled across the field. Flying continually from one rotational wind into another, and then another – low – was dizzying. At any point I could have climbed quickly and soared away, but that was not the point. I needed to know more about what was happening here and now, for next time.
As the storm moved on and abated I began to comprehend a bigger picture. This was one of those huge megadevils, the kind you normally see only in the middle of wide lake beds, a rotating ring of ordinary whirlies a half mile across.
Why did it boil up right at Crystal airport, and seemingly out of nowhere? Got me. But since you asked, discrete shear lines intersect often in these parts, quite benignly. On rare occasion though, they powerfully collide in a kind of atmospheric triple whammy. When I’ve been already aloft and that happened, the causes were obvious. Prior to this freak show however, I was on the ground and there were no clouds anywhere until…
Things settled out for a routine landing as the day’s only cumulus formed not far downwind, thank you very much. The flight was brief, never got a mile from the field, but I learned more in those twenty minutes than many whole days sailing high and dry in ‘ideal’ conditions. What more could anyone want?