Pterosaur ornithopters: lessons learned

Following in the success of the Dr. Paul B. MacCready‘s 1985 flying Quetzalcoatlus ornithopter (Fig. 4), a few years ago there was an attempt at getting another very complex pterosaur ornithopter to fly.

Margot Garritsen is a Dutch engineer and Stanford professor who led a team intent on building a flying pterosaur based on Paul Sereno’s ornithocheirid from the Sahara. They were counting on greater success with lighter materials and a more accurate wing movement with not one, but five wing joints for flight control. Several paleontologists were team members and Hall Train provided some of the mechanics. So it had everything going for it. The project was featured in the IMAX film “Sky Monsters.”

Figure x. The Stanford pterosaur ornithopter moments after dropping from its mothership. On this second attempt all the fur and non-essential material had been removed.

Figure 1. The Stanford pterosaur ornithopter moments after dropping from its mothership. On this second attempt all the fur and non-essential material had been removed. A removable horizontal stabilizer with twin rudders is added as a sort of stabilizing tail. Note, this is a deep chord wing membrane configuration, which pterosaurs did not have.

Unfortunately
the new and improved ornithopter failed to flap and failed to fly.

Another inventor, Kazuhiko Kakuta
using a much simpler design (Figs. 2, 3), created a successfully working ptero-ornithopter.

Cheaper. Simpler. Less accurate.
Actually, almost nothing is more pterosaur-like than bird-like here other than the fashioned crest. The key here appears to be the successful creation of sufficient thrust and lift without a cambered airfoil — as in any toy bird-like ornithopter.

For those interested ornithopters are explained here.

Figure 1. Pterosaur ornithopter. This model flies well and for good reason.

Figure 2. Pterosaur ornithopter. This model flies well and for good reason.

An efficient flapping wing must be able to flex and/or rotate: if a static wing is kept at the same angle while moving up and down, it will produce no net lift or thrust. Flexible wings can attain efficiency while keeping the driving mechanism simple. In Ornithopters its the ventral and dorsal curling of the wing during flapping that changes the wing shape and creates lift and thrust.

Read about the model maker here with his other pterosaur YouTube videos listed.

Figure 2. Click to see video. This pterosaur ornithopter folllows the basic plan of bird ornithopters in having a stiff leading edge and a flexible trailing edge. There's no need for complex flapping cycle. Up and down works pretty well.

Figure 3. Click to see video. This pterosaur ornithopter folllows the basic plan of bird ornithopters in having a stiff leading edge and a flexible trailing edge. There’s no need for complex flapping cycle. Up and down works pretty well.

Most ornithopters have extremely simple motions and deep chord wing shapes.

What would happen if the wing had a camber, a narrow chord and a spoon-shaped wing tips, as in pterosaurs? So far, except for the MacCready invention (Fig. 4), no one has built a short chord. long wing ornithopter and even the MacCready invention did not have the proper pterosaur wing shape and leg configuration.

So there’s an opportunity here to do something great for an engineering student: replicate a real pterosaur and make it flap using simple ornithopter techniques.

Figure 3. Quetzalcoatlus model ornithopter by Paul Macready getting walked to its take-off point.

Figure 4. Quetzalcoatlus model ornithopter by Paul Macready getting walked to its take-off point. The tucked in legs are based on the bird-like hypotheses of Dr. Kevin Padian, now widely regarded as wrong. No fossils preserve this configuration. Rather the legs would have been more or less splayed in flight.

Dr. Paul B. MacCready is famous for creating a dang big ornithopter the size and shape of a Quetzalcoatlus back in 1985. Here it is on YouTube. Here is a pdf of the project. It flew very successfully. There’s a Popular Science article here about MacCready’s work.

Still…
It would have been better to extend those hind limbs like horizontal stabilizers on airplanes (Fig. 5), but they were listening to Kevin Padian back then and he saw pterosaurs as very bird-like. Now that we know they were more lizard-like, pterosaur configurations have changed. 

Rhamphorhynchus model by David Peters

Figure 5. Rhamphorhynchus model by yours truly. Note the narrow chord long wings and feet splayed like a horizontal stabilizer. The raised elbows produce more camber proximally. The tail is an unnecessary secondary sexual characteristic.

For a change of pace, here’s a video that shows a small simple pterosaur-shaped airplane powered by propellers. So basically, it’s an airplane.

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