Pterosaur-inspired aircraft makes sharper turns

Jun 14, 2011 by Lisa Zyga feature
(Left) A pterosaur. Image credit: Logan’s Dino World. (Right) A possible configuration for a small aircraft with its vertical tail at the nose. Image credit: Roberts, et al. ©2011 IOP Publishing Ltd.

(PhysOrg.com) -- By morphing and repositioning a small aircraft's vertical tail to resemble the cranial crest of a pterosaur, researchers have shown that the aircraft's turn radius can be reduced by 14%. The ability to make sharper turns is especially important for small aircraft that operate in urban environments and in the presence of obstacles.

The team of researchers, Brian Roberts and Rick Lind from the University of Florida, along with Sankar Chatterjee from Texas Tech University, has published the study on the pterosaur-inspired aircraft in a recent issue of Bioinspiration & Biomimetics.

Although birds and bats are the only tetrapods that are currently capable of powered flight, the first vertebrates to achieve flight were . These flying reptiles (not technically dinosaurs) appeared about 225 million years ago and became extinct along with the dinosaurs about 65 million years ago. For those 160 million years, pterosaurs ranging in size from 12 grams to 70 kilograms roamed the skies. One thing they all likely had in common was a large, plate-like cranial on the tops of their heads.

While some researchers have suggested that the cranial crest could have had advantages for mating or diffusing excess body heat, the researchers here think that the large, vertical surface must have had an aerodynamic impact. In their study, the researchers developed a model of a small aircraft design that incorporates a vertical tail that is similar to the cranial crest of the pterosaur. Instead of placing the vertical tail at the back of the aircraft, the researchers allowed the tail to move forward all the way to the front of the aircraft.

The researchers’ model showed that moving the vertical tail to the nose of the aircraft can reduce the aircraft’s turn radius by 14%. This improvement is due to the fact that the conventional position of the tail requires the nose of the aircraft to point away from the direction of the turn, while the position of the tail on the aircraft’s nose requires the nose to point into the direction of the turn.

This advantage comes with a tradeoff, which is a decrease in the aircraft’s static and dynamic stability. However, the researchers showed that this tradeoff between performance and stability can be addressed by giving the vertical tail a capability that allows it to vary its position during flight.

In the models, the tail could not only range across the entire fuselage of the aircraft, but it could also rotate about its leading-edge axis by 45° in either direction, giving it a greater impact on the aircraft’s aerodynamics. For instance, the researchers found that the small aircraft could perform a “Dutch roll,” a maneuver that involves rocking from side to side. With these kinds of abilities, the aircraft could have a wide variety of applications.

“The applications of a pterosaur-inspired design cover the spectrum of uses already being adopted for UAVs [unmanned aerial vehicles], such as search and rescue, damage assessment, surveillance, drug interdiction, border security, and communication,” Lind told PhysOrg.com. “Essentially, the technology has potential benefits for aircraft that need to increase maneuverability and fly among obstacles. The pterosaurs had a vast range in wingspan and crest size, so a correspondingly large range of aircraft may benefit from the biological-inspired design.”

While previous studies have looked to birds and bats for inspiration for designing small aircraft, the results of the current study show that the pterosaur is also an appropriate source of inspiration. The results build on previous research, which has found the pterosaur configuration to be highly maneuverable and highly efficient for slower flight speeds.

“The pterosaur project is part of a large on-going effort into biological-inspired design at the University of Florida,” Lind said. “We will continue to look into concepts from birds, bats, insects, reptiles and pterosaurs for advancing flight capability. An early prototype has been built that augmented an existing vehicle with 24-inch wingspan by mounting a fixed tail into the nose. Flight tests will be conducted this year on that prototype along with construction of a vehicle with a tail that translates along the fuselage between the back and the front.

“A particularly welcome feature to this project is the ability to attract students from elementary school to college and show them an exciting application of engineering and math. We have several undergraduates that love to design the and associated morphing mechanisms which helps to teach aerodynamics, control, avionics, structures, and now even biology. The pterosaur project has been invaluable as a teaching tool while addressing a new area of the aviation community.”

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More information: Brian Roberts, et al. “Flight dynamics of a pterosaur-inspired aircraft utilizing a variable-placement vertical tail.” Bioinsp. Biomim. 6 (2011) 026010 (11pp)

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fmfbrestel
5 / 5 (2) Jun 14, 2011
Yeah... I dont think i would want to fly in a plane that had a tail section that moved up and down the length of the fuselage. To many moving parts to break down. Neat idea and teaching tool, horrible aircraft design.
richgibula
5 / 5 (2) Jun 14, 2011
If you view large birds or pterosaur models from behind, the shape looks like a curvy letter "M." Even on cartoons and paintings, that's how you can tell that the far-way object is a bird. I have never seen an airplane that imitates this aspect of wing design, but I don't have a clue why not. Does anyone have an explanation?
nayTall
2.5 / 5 (2) Jun 14, 2011
@richgibula - i'm only guessing, but probably because the vertical movement a bird's wings need is for propulsion, and a plane has engine(s). the only shape a plane's wing needs is a curved top and a flatter bottom side to allow for air-lift. it seems like an 'm' shaped wing-span would just be ripe for breakage / stress on the intersection at the body.
steve_v
5 / 5 (1) Jun 14, 2011
The 'm' shape is for stable flight. If you throw a paper aeroplane upside down it with flip or crash, throw it the right way up and it will gently float along.
The reasons aircraft don't use this are; it's very difficult to turn in this stable condition; it's not easy to engineer a fully moveable wing to return to an unstable configuration.
A plane's instability is what makes it maneuverable. The most agile, speedy air craft, like the eurofighter would crash and burn if it wasn't for its onboard computer correcting its flight.
It seems to me that it's far too complicated for engineers to create a completely 'biological' machine.
By the way pterosaurs have headcrests in all sorts of shapes, made out of all sorts of bones. This suggests they are for sexual display, since they clearly changes them dramatically with little effect on their flight. Not only this but male pteranodontids and wukongopterids have been PROVEN to posess headcrests, whereas females lack them, or display smaller one
pauljpease
5 / 5 (1) Jun 14, 2011
@steve_V,

yes, but evolution isn't engineering. Often an adaption that served one purpose ends up being multi-purpose. Maybe it started out as a purely sexual display, but selection for optimal flight characteristics also ended up shaping the design of the headcrests. Maybe females weren't as agile flyers, and maybe they didn't need to be. Maybe male pterosaurs fought their rivals in the air!
Telekinetic
1.3 / 5 (3) Jun 14, 2011
The human-powered ornithopter.
www.youtube.com/w...7j1imdhQ
Bob_B
not rated yet Jun 14, 2011
Better drone control over moving targets.
maxcypher
not rated yet Jun 15, 2011
I wonder if having vertical tails positioned at both the front and rear would be beneficial. The two would be coupled together for the most control.
DavidMcC
not rated yet Jun 15, 2011
Yeah... I dont think i would want to fly in a plane that had a tail section that moved up and down the length of the fuselage. To many moving parts to break down. Neat idea and teaching tool, horrible aircraft design.


Fmfbrestel, you may have misinterpreted the article where it referred to "moving the tail...". I could be wrong, but I think that would have been something that only the designer would do, not the pilot!
DavidMcC
not rated yet Jun 15, 2011
@steve_V,

yes, but evolution isn't engineering.


Another interpretation is that it is, but with more complex design criteria than an engineer used to machines designed for one specific function might assume.
DavidMcC
not rated yet Jun 15, 2011
... I should add that I see natural selection as a non-conscious designer, using a method similar to the so-called "evolutionary genetic design algorithm" approach used nowadays to optimise eg, military wing designs and some electronic circuits.
mjesfahani
not rated yet Jun 16, 2011
Still there are many creatures we must make our crafts from them.
DavidMcC
not rated yet Jun 16, 2011
Although people have been learning about engineering solutions from living species for some time, it is less common to be learning from long-extinct species like pterosaurs. It shows the practical value of studying evolution.
Seramonial
not rated yet Jun 16, 2011
Like a front-wheel drive Mini Cooper car
antialias_physorg
not rated yet Jun 18, 2011
Yeah... I dont think i would want to fly in a plane that had a tail section that moved up and down the length of the fuselage. To many moving parts to break down.

You are scared of helicopters, then?
rwinners
not rated yet Jun 21, 2011
The first thing that occurred to me when I saw the accompanying drawing was that mass has been moved.
I wonder if that has something to do with it.
DavidMcC
not rated yet Jun 21, 2011
The first thing that occurred to me when I saw the accompanying drawing was that mass has been moved.
I wonder if that has something to do with it.

Isn't that just a definition of "re-design"?