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Inch - epaper ⋅ Ausgabe 2/2020 vom 12.06.2020

Otto Lilienthal and Wilbur & Orville Wright are considered to be the fathers of flight: Despite the fact that they are long dead and never met in real life, Markus Raffel managed to arrange a meeting of the aeronautical giants: Last December, his replica of a Lilienthal glider and a Wright glider flew side by side for the first time. This is the story of how Otto, Wilbur & Orville finally met on a famous dune in North Carolina.

Artikelbild für den Artikel "FIRST FLIGHT: WHEN OTTO MET WILBUR … AND ORVILLE, TOO" aus der Ausgabe 2/2020 von Inch. Dieses epaper sofort kaufen oder online lesen mit der Zeitschriften-Flatrate United Kiosk NEWS.

Bildquelle: Inch, Ausgabe 2/2020

Markus Raffel’s (second from right) Lilienthal glider and a Wright glider are ready for their historic flight side by side.


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... Fliegekunst: Otto Lilienthal und die Gebrüder Wright, Wilbur und Orville. Obwohl sie schon lange tot und sich zu Lebzeiten nie begegnet sind, gelang es Markus Raffel die Luftfahrtgiganten zusammen zu bringen: Letzten Dezember flogen die Nachbauten eines Lilienthal Gleiters und eines Wright Gleiters zum ersten Mal Seite an Seite. Dies ist die Geschichte, wie sich Otto, Wilbur und Orville auf einer berühmten Düne in North Carolina getroffen haben.

“Lilienthal crashed but the Wrights got it right.” A rather simplified statement about the beginnings of heavier-than-air flight, to say the least. Then again, a tour guide at Kitty Hawk, the Wright’s old flying area, might be forgiven for being overwhelmed by national pride - and a hard-to-resist alliteration. Yet, it wasn’t so much the guide’s simplification which bugged Markus Raffel on his tour but the fact that outside Germany Otto Lilienthal seemed to be better known for his failure than his seminal work.

Prof. Dr. Markus Raffel is Head of Department at the DLR Institute of Aerodynamics and Flow Technology. He’s also a sort of ‘Lilienthal apprentice’ with a mission to change the perception of the great flight pioneer. Raffel first came into contact with Lilienthal’s work when he supervised a follow-up PhD thesis to a large research project from 2016.

125 years after his first historic flight, the DLR wanted to clarify once and for all how flightworthy Lilienthal’s glider really was. After a lifetime of researching the mechanics of flight, building dozens of monoplanes, biplanes and ornithopters and testing them in over 2,000 flights, the great aviator fatally crashed with his Normalsegelapparat, or normal soaring apparatus, on 9th August, 1896. Ever since, the question whether this was the result of a fundamental design flaw or a pilot’s error has remained unanswered.

To see if Lilienthal was ‘right or wrong’, the DLR had a replica of the normal soaring apparatus built and rigorously tested it in one of the world’s largest wind tunnels in Emmeloord in the Netherlands. The tests were unequivocal, the glider proved to be astonishingly stable and airworthy in the wind tunnel. “It withstood wind speeds of up to 36 kilometres per hour, delivering datasets that would not look out of place in any textbook. The flight characteristics are similar to those of the primary gliders of the 1920s and 30s - designs that remained in use decades after Lilienthal,” recalls Andreas Dillmann, head of the DLR Institute of Aerodynamics and Flow Technology.

An admiration shared by Dillmann’s colleague Markus Raffel, who, after supervising the thesis, caught the ‘Lilienthal bug’: “It’s the combination of Lilienthal’s knowledge of aerodynamics, his craftsmanship and body control which I find so appealing.” Raffel hatched a plan. He wanted to prove the normal soaring apparatus’ flightworthiness - not in theory, but in practice. He wanted to fly one.

In an early concept of the 2016 research project, a Lilienthal glider, piloted by a stuntman, would have been dropped at altitude from a helicopter as the ultimate proof of its flightworthiness. Luckily, the idea was abandoned - besides being an insurance nightmare it would have been a certain disaster. “Lilienthal’s gliders were designed to fly in a straight line at low altitude,” explains Raffel. So, for the sake of historical accuracy - and his own life - he skipped the helicopter. Since the flight would be his own personal project anyway he, instead, opted for a slow and methodical step-by-step approach - just like Lilienthal did some 130 years ago.


First, of course, he needed a glider. The one from the wind tunnel test was spoken for and it would have been too small anyway. So he had a replica of a ‘Normalsegelapparat’ built by the Lilienthal museum in Anklam. Lilienthal’s original drawings and detailed building instructions have survived and the team at the museum had built quite a few gliders in accordance with them for other museums before. “We only had to increase the wingspan by half a meter to account for my larger size and weight compared to Lilienthal,” admits Raffel.

Becoming Lilienthal: Markus Raffel had a Lilienthal glider built by the Lilienthal Museum in Anklam. He then learned to fly in the wind tunnel and on a self-made platform. In California he finally performed the first, untehtered flights of a Lilienthal glider in almost 130 years.

The rest, however, was as original as it could be all the way down to the materials: willow branches, pinewood, steel wire, hemp rope - even the hemp cloth for the wing covering was woven on historical looms from the era.

While Lilienthal’s instructions on how to fly the glider were equally well documented, Raffel actually never bothered to read them. He wanted to learn it just like Lilienthal did - admittedly in a very 21st century kind of way.

Since he had never flown a glider before he thought it might be a good idea to get at least a beginner’s hang-gliding licence. Then he mounted a five-by-five-meter platform to an old trailer, strapped the glider to it and had an assistant towhim behind a car for his first cautious hops. This low-cost version of a wind tunnel proved to be most useful. “Although Lilienthal had meticulously documented all his flights he never really mentioned the importance of trimming,” explains Raffel. For a stable flight the glider’s centre of gravity has to be in front of the aerodynamic centre. “Slowly we learned to adjust the trimming by adapting the tension of the wires, adding trim weights here and cutting away some of the covering there. Body posture also plays an important role.”

Steering a ‘Normalsegelapparat’ is somewhat different to steering a hang-glider. In the latter, as the name suggests, the pilot hangs in a harness and controls the aircraft with his arms via the control bar. In a normal soaring apparatus, however, the pilot rests his weight on two armrests and uses his legs for steering. To better learn the intricacies of this technique, Raffel entered the next phase of his do-it-yourself flight training: scooter-towing.

Since a regular glider winch would be too powerful for the delicate normal soaring apparatus, the modern day Lilienthal apprentice converted an old scooter into a winch. Even though towing is more like flying a kite than free flight, it nonetheless allowed Raffel to master the tricky and somewhat counter-intuitive steering transition between running and flying.


Finally, with the aerodynamics approved by the DLR, a normal soaring apparatus built exactly to Lilienthal’s standards and weeks of tethered flight training, everything was ready and set to attempt the first free flight. Unfortunately, Raffel was grounded by forces stronger than any physics: German flight regulations. To get an experimental flight licence the ‘Normalsegelapparat’ should paradoxically not be classified as a hang-glider - which it basically is. “In the US, however, it’s the other way round,” sighs Raffel.

Thankfully, Lilienthal had the foresight to design his glider light and foldable enough to fit into the baggage compartment of a modern airliner. So Raffel had a little excess baggage when, in 2018, he arrived in California for a three-month sabbatical at Caltech. It didn’t take him long to find the perfect spot for his endeavour: Marina State Beach near Monterey, a hang-glider’s paradise with soft dunes and constant wind. It was here, on the 3rd April, 2018, where Raffel finally had his ‘Lilienthal moment’: After a lot of running down dunes and a few tentative hops a ‘Normalsegelapparat’, for the first time in almost 130 years, glided freely through the air. Raffel had recreated a defining moment in our technological evolution: the first piloted heavier-than-air flight.

Well, sort of: The flights only lasted a couple of seconds and were no longer than 70 metres. Nonetheless, Raffel had caused quite a stir - then again, it’s hard not to when you show up with a flimsy willow and cloth contraption in a hang-glider’s hot spot. Soon Raffel learned that, at least among hang gliders, Otto Lilienthal and Francis Rogallo were considered to be the forefathers of the sport, but not so much the Wright brothers. This respect for Lilienthal’s work only deepened after others had tried the normal soaring apparatus. “When I fly a hang glider, I have an umbilical cord connecting me to the wing. But in the Lilienthal, I am the wing. It’s a pure bird-like feeling,” recalls Andy Beem, owner of a hang gliding school in Los Angeles, when talking about his first flying experience with the original item.


…see highlighted examples in text.

HAD is used in a number of different ways:
Past tense of have: I had a day off yesterday.
Past tense of have to: We had to delay the launch because of technical problems.
Past perfect auxiliary: When I arrived the meeting had already started.
Causative have in the past: We had the heating replaced in our house.

//// EXERCISE ON PAGE 53 ////

On the 14th December, 2019, the first heavier-than-air craft - the gliders of Lilienthal and the Wright brothers - flew side by side for the first time.


The fact that Raffel had ultimately proven Lilienthal ‘right’ was, however, only the beginning of a quest to further understand and promote the flight pioneer’s work. In 2019, Raffel returned to the US, this time with a replica of Lilienthal’s ‘Großer Doppeldecker’, or big biplane. Between flight tests Raffel toured some ‘first flight’ sights. He visited the National Air and Space Museum, where he was allowed to laser scan one of the few remaining original Lilienthal gliders purchased by the American newspaper publisher William Randolph Hearst, who had it flown in 1896 in New York. Naturally, Raffel also went to see one of the holy grounds of flight: Kitty Hawk. Here he had the chance to fly the ‘other glider’. Since 2011 the Kitty Hawk Kites Flight School has offered the unique experience of short tethered flights with a replica of a 1902 Wright glider. A flight and a few careless words from a guide later, Raffel had an idea: How about a side-by-side flight of the two gliders? How about a meeting between Otto, Wilbur and Orville?


The giants of flight never met in real life. As a matter of fact, Lilienthal was already dead when the Wrights started to work seriously on a flying machine of their own. The two bicycle mechanics were, however, intimately familiar with his work and probably knew his 1889 reference book ‘Bird Flight as the Basis of Aviation’ by heart. Wilbur Wright even once said that “of all the men who attacked the flying problem in the 19th century, Otto Lilienthal was easily the most important. He was without question the greatest of the precursors, and the world owes to him a great debt.” Despite all that, the brothers’ approach turned out to be completely different: a biplane, right from the start, with long rectangular wings on which the pilot was lying. Most importantly, however, the Wright glider had mechanically operated control surfaces.

So how do the two concepts compare? To find out, on 14th December, 2019, two men stood on a dune in North Carolina not far from Kitty Hawk: Raffel’s friend Andy Beem in the Lilienthal big biplane and Billy Vaughn, an instructor from the Kitty Hawk Kites Flight School on the Wright glider. It was a perfect setting for this historical meeting: blue sky and favourable winds. A few more checks and then the signal from Beem: “Launch!”

For a brief, magical moment the two historic aircrafts were in the air together only some 30 metres apart. No-one cared about right or wrong, first or second, failure or success. For a brief moment, in the recreation of an alternate history, the great flight pioneers were together, opening a new realm for humanity to explore: airspace. Billy Vaughn put the significance of the moment into words: “I had the presence of mind to look out over the left wing to see the Lilienthal glider flying next to me. It dawned on me after the flight that that’s a view no-one had ever had. Ever. Very humbling, actually.”

An experience that was asking for an encore: The teams repeated the flights several times and returned the day after for more. Everyone wanted a go to check out the two gliders. So which one is better? “The Lilienthal is the animal. The Wright is a machine,” Raffel sums it up in a Solomonic judgement. But then again, who cares when you can have fun with history on a dune.

Matthias Meier Kurze DLR Beiträge über das Projekt Lilienthal-Gleiter, die Erstflüge und den Parallelflug mit dem Wright-Gleiter. Podcast mit Markus Raffel über seine Flüge mit den Lilienthal-Gleitern. Homepage des Otto Lilienthal Museums in Anklam, wo der Gleiter für den Parallelflug gebaut wurde. Webseite von Kitty Hawk Kites, wo man unter anderem einen Flug mit einem Nachbau des Wright-Gleiters buchen kann. Artikel des Air & Space Magazin über den Parallelflug der Gleiter.

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Trimming an aircraft refers to the adjustment of the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input. It allows the pilot to release the control input without the aircraft deviating from the intended path. Most aircraft have single axis trim for the elevator - usually a small trim tab connected to the trailing edge of the control surface. Airliners have a three-axis trim for the elevator, rudder and ailerons.

On most aircraft, the centre of gravity of the airplane is located near the centre of pressure of the wing. If the centre of pressure of the wing is aft of the centre of gravity (cg), its lift produces a counter-clockwise rotation about the cg. To trim the aircraft it is necessary to balance the torques produced by the wing and the tail. If the tail lift is slightly negative, it produces a clockwise rotation about the cg, which can balance the wing rotation.