The Magnus effect can cause interesting things to happen to spinning basketballs. In short, the Magnus effect is an air pressure differential that causes an object to essentially “lift” in the air. Some of you may have realized that this is what an airplane’s wing does - and indeed, someone realized that a spinning cylinder can be used as an airplane wing.

Anton Flettner, US Library of Congress Photo, uploaded to Wikipedia by “VladiMens”

That person was Anton Flettner, a German aerospace engineer back when “aerospace engineer” was a completely new field of study. Thus he was in a position to pioneer a number of gadgets and concepts even the most basically-trained pilots today take for granted, but right now we’re more interested in his most far-out creation, the Flettner Rotor. The concept is actually pretty simple: instead of a spinning basketball using the Magnus effect to put distance between it and a dam wall, a Flettner Rotor uses a power source (such as an internal combustion engine) to spin a long cylinder (say about the length of what a conventional wing would otherwise be) to use the Magnus effect to put distance between an aircraft and the ground.

In terms of how a casual observer on the ground would see things, this is how a conventional wing works anyway, but with two key differences - one, an airplane wing is using the Bernoulli effect which is a different principle but as far as a pilot sitting in the cockpit is concerned the end result is the same. But unlike a static Bernoulli effect wing which requires pushing the wing through airflow in order to achieve lift, a Magnus effect Flettner Rotor can theoretically achieve at least some degree of lift even when the aircraft itself remains stationary relative to a fixed ground point. This means shorter take-offs at the very least, and theoretically complete vertical take-off like a helicopter. The trade-offs compared to conventional Bernoulli-effect aircraft would be either shorter range or greater fuel carriage given that you now need to constantly power that spinning wing or fall out of the sky, but compared to conventional helicopters it should represent better range and efficiency overall.


Flettner constructed a single aircraft (or more, apparently nobody legitimately knows) to test his rotor theory, shown at left in the only image I could find (an image owned by the San Diego Air & Space Museum which they have given free license to disseminate, here taken from Wikipedia uploaded by “The Bushmaster”). Speaking of which, Wikipedia states that “there was no record of them ever having flown” and further Google searching research has failed to verify or contradict this claim. That said, R/C aircraft hobbyists have constructed their own successful Flettner Rotorwing aircraft and YouTube videos of these models in operation are plentiful.


Image from U.S. Library of Congress, uploaded to Wikipedia by “Balcer”

The story of Anton Flettner and his rotor doesn’t end with the maybe, sort-of mysteriously aborted flight of his aircraft either. He also adapted the design to power a schooner named Buckau and later Baden-Baden which was successful. If you realize that a propeller (or rotor) is just a rotating wing, it gives you some idea of how a rotorship works with Flettner rotors in place of giant propellers mounted on the ship in the same way a Flettner rotor works vs. a Bernoulli wing. Theoretically it would work if the rotors were placed underwater too (similar to a Voith-Schneider propeller) but it seems that most of the applications have the rotors working against the air. Most of these applications seem limited to personal craft and other “quirky” vessels, but wind turbine manufacturer Enercon has a vessel called the E-Ship 1 used to deliver wind turbine parts to off-shore locations. E-Ship 1 uses four Flettner rotors to supplement two conventional underwater propellers.


Public Domain image uploaded to Wikipedia by “Stahikocher”

As for Anton Flettner himself, he never gave up on vertical or short-take off craft, but decided to concentrate on helicopters instead. He was particularly fond of intermeshing rotors - two rotors sitting next to each other that avoid hitting the other through synchronized timing much like your kitchen’s eggbeater. He also continued to develop aircraft in Germany, which means his designs ended up seeing service with Nazi Swastikas painted on their tails. The most successful of which was the Fl 282 Kolibri (Hummingbird, a popular model name for helicopters all things considered that Airbus still uses today), a light single-seat machine. Some sources have claimed that it would’ve been armed with machine guns and been a powerful attack machine, but considering its small size, short range and speed it wouldn’t have been able to carry much ammunition and would be a flying flak magnet under serious battlefield conditions. Actual research suggests it was mostly intended as a flying observation point and to deliver cargo via sling-load much like helicopters today. Few were made, and by the time they were the war conditions that accommodated their safe use disappeared.


Image Public Domain, uploaded to Wikipedia by “Kristianrj”

After Germany’s defeat, Flettner was whisked away to the United States where he continued to develop helicopters for Kaman Aircraft. His intermeshing rotor design survived into the HH-43 Huskie, the primary means of rescuing downed USAF pilots in Vietnam. Today the K-MAX uses this design to achieve heavy lift sling-loads onto a very small and compact design.