Bill Crawford’s Flightlab Blog

I think that flight instructors should have calm and reassuring demeanors. From a marketing standpoint, at least, they should know when they’re coming across as lunatics. I appreciate all that, but the rain is driving me nuts. One can’t fly aerobatics when the ceiling is perpetually 300 feet. I’m grounded, grumpy, and headed for lunacy. Please, let the rain stop!

The subject of May’s column was April’s “Smilin’ Jack” comic strip. I’ll try to get this straight: In April, Jack was shown flying his tri-motor in extreme turbulence over the jungle, through the aptly named Hurricane Pass, when the cement mixer he was carrying broke loose (sabotage, again). In the May “Flightlab” (written in April, after the April edition appeared), I wondered if Jack would have slowed below maneuvering speed while in the turbulence, since that concept appeared to be absent from the training literature at the time the strip was written. I figured the May installment of “Smilin’ Jack” would pick up the tale, with the cement mixer still bopping around, and I could use the opportunity of Jack’s travail to write in May (for June) about how a rapidly shifting center of gravity might affect flight behavior. Well, it seemed a clever notion at the time, even though I’d be a month behind, talking this month about what happened last month. I’m not sure I’d figured that out.

But in May’s Flyer, Jack had already landed and the story of his survival was left unexplained. It could be that the “Smilin’ Jack” album the series is swiped from each month skips forward, so no one at the Atlantic Flyer is to blame for the jump in the story—since the jumping had already been done. That’s nonsense. Someone at the Atlantic Flyer is always to blame. I have no idea what Jack is doing this month. He was scheduled to be eaten by piranha. I hope he survives the new design layout. The Flyer looks better, don’t you think?

Anyway, May’s “Smilin’ Jack” contained a sketch of the tri-motor being hauled away on the ground. The scale was weird. As depicted, the aircraft was either surrounded by giants or had shrunk to miniature. Props were bent; wings had wrinkles. But more to the point, it had a substantial hole in the top of the fuselage.

My forensic conclusion is that the cement mixer made that hole. I’ll bet the aircraft got knocked inverted by the turbulence and the cement mixer bid farewell through the ceiling. It makes complete sense. The floor would be reinforced for cargo, but not the ceiling—certainly not for cement mixers. Of course it’s possible that Jack caused this himself, relying on his superior airmanship and his technical intimacy with structures and materials. It would have been brilliant had he actually rolled the aircraft to rid himself of the center of gravity problem. But I suspect it was an upset caused by the kind of sharp-edged gust we’ve all experienced in jungle passes. If you have other information, send me a line.

One might think that the problems caused by unrestrained cement mixers during extreme turbulence would be well covered in the literature. Surprisingly, in none of the aerodynamics texts on my shelf does the index include “cement mixer.” There’s plenty on weight shift as used to adjust stability characteristics, for instance to counteract the pitch instability as the B-58 Hustler goes supersonic, or on the pumping of fuel aft in transports to reduce trim drag. But useful studies regarding cement mixers are not found, even as footnotes.

The subject would seem perfect for the Googlebots that chase the expanding sum of human knowledge. I just finished Googling the words: cement mixer, turbulence, aircraft. Guess what came up number one—last month’s “Flightlab” column, as it appears on my blog! You’d think the Googlebots could do better.

Although a search using the string of words above didn’t produce any insight into how aircraft behave in severe turbulence when the center of gravity shifts due to the movement of a cement mixer, it did underscore a popular metaphor. Numerous citations remind us that people quite often describe the experience of severe in-flight turbulence as that of being inside a cement mixer. Most, of course, have never been inside a cement mixer and aren’t qualified to offer detailed observations. But don’t quibble—the point they make is vivid and unmistakable, and that’s all a metaphor (or even a simile) has to do to get a drink in this town (hey, another metaphor).

The rain has robbed me of seriousness and purpose. I’m supposed to write about aerodynamics, but the best I can offer is speculation on the tiny subset of folks who’ve actually experienced both the turbulent ride inside a cement mixer and the ride in turbulence in an aircraft. There can’t be more than a handful, unless there’s a Pledge Night I don’t know about. But I bet nobody has ever been simultaneously inside a rotating cement mixer while in an airplane in turbulence. I wonder how much that would cost. We could get a group together.

The rain blurs the lines between fact and fiction. So I worry about the effect of a cement mixer, descending at terminal velocity, on the emotional wellbeing of the remote jungle tribesmen down below. Will they have to revise their mythology to explain stuff arriving in a vertical trajectory? Or do they already believe that the parts of creation that didn’t rise from Mother Earth were jettisoned by Father Sky, just not so recently? Would they charge other tribes admission, or would they cordon off the area and keep the cement mixer a secret—except from those who have undergone a painful initiation ceremony? A month from now, let’s send the Googlebots to find out. Who knows what they’ll bring back?