Some research articles are a confusing compendium of calculations, obscurely labelled diagrams, and carefully hidden conclusions. Yes, the journal Bioinspiration & Biomimetics generally publishes articles that look exciting on the outside, but the soft chewy center is an acquired taste. Nevertheless, the combination of dinosaurs and planes had me take two aspirin in anticipation of the oncoming headache before I dove right in.

When we think of pterosaurs, we tend to get a Hammian vision (I don't understand a word of the dialogue, but I so want to surf on the back of a pterosaur). But pterosaurs occupied many flying niches and ranged in size from about 12g to 70kg. The smallest of these were likely able to hover and probably had to be highly maneuverable to catch food.

What makes the pterosaur particularly interesting, though, is that it had a huge, vertically oriented crest on its head. This is in contrast to modern flying species, which either have no (or very small) vertical stabilizers. The utility of such a crest has been argued among paleontologists since pterosaurs were uncovered. But surprisingly, no one seems to have investigated how the crest affects their ability to fly.

I am now happy to report that this has been rectified, with a triplet of researchers from the University of Florida and Texas Tech University getting the ball rolling. In particular, the researchers were interested in how the crest would effect the maneuverability of smaller pterosaurs and how its function might influence the design of small autonomous vehicles.

The investigation itself used a numerical model based on a preexisting model airplane. The idea is that the weight distribution and performance of the airplane are already known, so a numerical model of that plane has already had extensive verification. The researchers can then have some confidence, provided they understand the limits of their code, in the predictions made by modified versions of the numerical model.

Essentially, what they did is move the tail fin of the virtual aircraft from aft to fore, and then calculated the flight stability and turning characteristics. As an additional test, they also shifted the vertical stabilizer up and down (so in some cases it was poking out the bottom and in others out the top) to see if that made a difference.

Not unsurprisingly, the roll stability of the plane was significantly affected by the vertical stabilizer. Moving it forward reduced the stability significantly, and shifting the stabilizer so it poked out the bottom made the plane unstable. So if pterosaurs were to have this sort of decoration, it had to be on top of the head. Even then, that crest comes at a cost, because reduced stability means more work to stay in the air.

The question is: what's the payoff? One potential payoff is in the rate of turn. The researchers' calculations showed that forward placement of the vertical stabilizer could increase the rate of turn, resulting in the radius of curvature reduction of some 14 percent.

In terms of catching prey on the wing, that increased maneuverability could well be the difference between going hungry or not. But there is no other evidence to back this up as of yet. Indeed, the researchers are not so bold as to draw this conclusion, merely noting that if a payoff from the crest was required, which it isn't, then this is one option.

Instead, the researchers intend to draw on these findings in the design and testing of new micro autonomous vehicles. I also hope that someone puts in the work to come up with a model that is a more realistic match to a pterosaur, because those beasts are just too cool to be ignored.

Bioinspiration & Biomimetics, 2011, DOI: 10.1088/1748-3182/6/2/026010

Listing image by Image courtesy of NASA