The elfin Story

Success is the glory of the effort

The innovative e-motor glider Stemme elfin is the advanced-career masterpiece of lifelong aviation enthusiast Reiner Stemme

Stemme’s latest aircraft is once again sleek and technologically forward-looking. Yet pushing forward its root concept to arrive at a cutting-edge electric motor glider spanned the entire professional life of its inventor. His vision of a glider capable of taking to the skies by own motor power and a plane suitable for relaxed “safari” tours had brought Stemme into developing aircraft as a young man. Some unique features of the new elfin model, the retractable propeller, foldable wings or side-by-side cockpit, had therefore debuted in a legendary precursor – the STEMME S10 motor glider that, since launch in 1990, became a household name in aviation circles for its outstanding technology and performance.

So, even if the new e-powered plane brings another edge to glider flying, it is built on ideas and technologies carefully iterated over decades by one of Germany’s most prolific aircraft designers. At age 81, Stemme still stands by the trademark “mankind needs wings” mantra he coined as a little boy. Born into a technology-minded family, the three words became a creed once he found himself parked by his elder brothers on top of a wardrobe to prevent him from taking part in their “prototyping” of all sorts of apparatuses made from cardboard, paper, straws and glue. Not being able to overcome gravity was an awkward feeling fanning his urge to turn aeronautical dreams into reality. “Believe it or not – this was my career-building moment. I was only five years old. From then on, I wanted to be involved in designing high-performance aircraft and nothing else”, he recalls sitting behind his desk at’s headquarters at Schönhagen airfield in Brandenburg, Germany.

Truly innovative glider designers hang on to their visions from young age

The winding path from the child with a knack for technology, growing up in sleepy 1950ies Philippsthal, to the mild-mannered octogenarian who launches his latest aircraft model to a global glider audience, resonates in many ways with modern-day tech innovator careers. “Being stubborn, setting your determination, vision and energy squarely against the unavoidable wall of scepticism, was as effective for getting things done as it is today. Only this can raise enough enthusiasm and sufficient funding to bring entirely new aircraft types to market”, Stemme says. “I surely know how much I owe to the numerous investors and aviation enthusiasts who loyaly stand behind my projects for decades now – and I hope the results and success we have is a satisfying dividend to them.”

Like other contemporary innovators, Stemme passed critical career milestones at a tender age while choosing risky turn-offs in his later life. Building model planes from early childhood, Stemme was only a teenager when he put together his first real glider aircraft during the off-time hours from his apprenticeship as a fitter in a local potash plant. Being one of the youngest members of the newly-founded aeroclub Segelfliegergruppe Kaliwerk Hattorf, he choose the blueprints of a Rhönlerche, a well-known German aircraft model designed by Alexander Schleicher. “Building this type of glider, I learned a lot about every aspect of aircraft construction. I took my first pilot training on this plane at the age of sixteen. Hence I knew it inside out”, he recalls.

Cold war colliding with red-hot developer enthusiasm sparks pragmatism

Feeling still limited in his options, Stemme made the most of the financial tailwind his siblings offered for his further education. He took evening classes, earned a high school degree and capped his educational sprint with an MA in physics from the prestigious Berlin Technical University (TU). “Analysing nature at very fundamental levels, gives you a deep understanding of all you need to know for designing aircraft”, Stemme says. He earned his formal glider license in 1963 after joining the Akaflieg Berlin, the TU’s glider club where student members would hone their skills as aircraft innovators. There, he spent as much time as possible at the controls in glider cockpits. Pursuing his passion helped him to find out as much as he could on the behaveiour of different airframes‘ in different thermal and weather conditions.

“Flying, though, was far from an easy undertaking in the cold-war days as the airspace above West Berlin was open to allied aircraft only. We had to decamp to a little airfield near Celle in West Germany to gather experience, study various aircraft and learn”, Stemme recalls. The Akaflieg club was well known for building self-designed prototypes at advanced technological levels. Conducting the necessary research during the dark winter days, its members tried to maximize their flying hours in the summer. This unique environment of flying, testing, researching, designing and adapting sailplanes along with other enthusiasts,  shaped him deeply. “It gave me the self-confidence to really see what is feasible in glider construction and to eventually come up with my own designs and features. I can safely say: the elfin is still benefiting from my time at Akaflieg”, he says.

Flying propelled and in soaring mode with one aircraft would resolve ‘Hirth’s dilemma’

From the start of his career Stemme was convinced that Wolf Hirth’s 1930’s dream of recreational cross-country flying in a high-performance glider would sooner or later become reality. The vision of Germany’s ‘godfather of gliding’ could come true with an airplane that ties self-powered flying to excellent soaring capabilities, Stemme reasoned. “In those days solutions fell into two categories. You would either extend the wings of a powered plane to improve its soaring profile. Or you could add a small engine to a sailplane, which brought about its own troubles, such as the dodgy weight distribution plus the unavoidable drag when the engine is put into its optimal position. None of this options was very efficient”, Stemme says.

From early on Hirth’s dilemma sparked a fire that would never die down in Stemme’s mind. The enabler in him, the plane designer who resolves things once and for all, put eventually forward a viable construction idea that morphed into workable, market-ripe concept in only a few months of head-scratching and napkin scribbling about systems, aerodynamics, engine shapes and airframe designs. To keep the glider’s balance uncompromised, the motor would be placed mid-ship and its power transmitted to a retractable front-propeller via a drive shaft running between side-by-side pilot seats. “This was a breakthrough”, he says. „It allowed for an aerodynamically clean fuselage during soaring flight but also for instant access to engine power if needed – while drag and trim remained untouched”. He rushed to get the fruit of this light-bulb moment patented straightaway. It was an invention that, much later, helped Stemme to get awarded the exclusive Otto Lilienthal Medal for his life achievements as aircraft designer in 2015.

The elfin glider rises from a cradle prominent ancestor models had soared from

Before Stemme tackled Hirth’s dilemma though, the aircraft manufacturer in waiting moved with family and two kids to Switzerland to earn a doctorate in physics at the university of Bern while having  a stint at a local laser manufacturer for the watch and medical industry. The added academic degree opened up new career paths and the family decided to relocate to Germany again where „Dr. Reiner Stemme“ took over the management of a VDI Technology Center – a precursor of today’s business incubator and accelerator hubs where he allocated funding and controlled the performance of young technology start-ups. It was an occupation that also led him register first patents covering crucial features of his envisioned aircraft concept.

Stemme knew a thing or two about nurturing businesses to success when he started Stemme Ltd, his own aircraft firm in Berlin. It was a career point where he went full risk as he took the plunge to commercialise his new aircraft brainchild rather than pursuing a safer career grounded on his solid scientific education. The upstart firm was up and running at a former AEG plant in Berlin’s Wedding district from 1984 after it was granted a special licence for building aircraft on West Berlin soil from the allied forces to make Stemme the one and only plane maker in the walled city. Its team worked day and night towards launching Stemme’s first motor glider model S10, with prototypes again moved to West Germany for test flights. Looking back he can laugh about the awkwardness of this approach.

“You can imagine the ballyhoo and paper work it meant to get whole planes over hundreds of road kilometers and through hostile GDR border checks to Westdeutschland and back to Berlin again.” Still it took the firm’s head designer and team just two years to get its new aircraft class ready for takeoff. Self-launching and fossil-fuel-powered it passed its maiden flight in July 1986 whit full certification following in 1990. The S10 formed the technological root for other aircraft Stemme has developed ever since – from model S6, an outlier single engine plane, to the e-powered elfin whose maiden flight is now imminent. “No winch, no aerotow anymore. We married launch independence with long distance capability. It became our main marketing line for our aircraft which globally sold more than 300 times. Without S10’s success we would not have been able to push our ideas forward to arrive at our current design”, Stemme remarks. The S10 model even earned him a visit on deck of the WWII US aircraft carrier ‘Intrepid’ where Stemme received the American Popular Mechanics Award for his innovative aircraft concept.

Performance, contemporary comfort and safety are merged in Stemme’s new e-motor glider

On an imagined ‘tree of life’ of aircraft concepts and solutions Stemme has come forward with in his long design career, model elfin would still make a new branch. “Yes, the plane is based on many features glider pilots will know from the S10. Yet numerous innovations and state-of-the-art technology make it a ‚giant leap‘ aircraft type”, Stemme insists. “The trademark collapsible propeller is now fitted with three blades in full carbon and with improved aerodynamics. The foldable wings got likewise improved. And if we think of the new e-propulsion unit or the added performance, handling and safety features, elfin is clearly a beast of its own”. The availability of much stronger batteries powering highly efficient propulsion systems allowed Stemme to get e-power into his new plane. “It is not anymore about where the drive shaft goes. The propeller gets now moved by a compact motor sitting right behind the plane’s nose, giving passengers in the cabin even more space and calm to enjoy the real glider feel”, he explains. Deeper than ever before Stemme embedded, his current design firm, into a european-wide supplier network – a modern approach to bring high-tech products to market at speed and in the highest available quality. The company’s ‘agile’ ecosystem delivers components such as elfin’s propeller blades from France, wings from Poland as well as an electric engine and generator made by Slovenian specialists.

The elfin is only just the start of a journey to an even wider horizon in aircraft building

Environmentally friendly, the elfin offers more performance in e-powered flight than any other electric motor glider on the market. And it still can enlarge its reach considerably via an attachable fuel-cell engine that allows for a non-stop 460 air miles range – roughly the distance between Berlin and Paris. “We considerably heightened air safety too”, Stemme adds. “The elfin is fitted with a rescue system that would vertically land the aircraft, suspended from a single parachute, in case something goes wrong mid-air. Plus, we picked a cockpit with the highest possible crash safety properties.“

Pulling all this off, getting all regulatory greenlights while making sure that all falls into place once elfin starts normal series assembly in due course, is quite a task for an octogenarian who is an active member of Germany’s venerable aviation club “Alte Adler” (Old Eagles) and whose fitness compares favorably to many of his age group. What is for sure, though, is that the Stemme family has a thing with flying. And there is even a vague dynastic horizon emerging for the firm, as Stemme’s elder daughter Karen Stemme and her elder son Simon, are likewise involved in aviation beyond holding a mere private pilot licence. Yet for now it is Reiner Stemme harboring plans for building aircraft even beyond elfin. A string of further designs already cram the drawers at RS.Aero. “We live in an age of breakthrough technologies. Their possibilities are amazing and it is my great challenge to point their way out into aviation”, he remarks with a smile, rushing out of his office to hold a meeting with his design team. If mankind needs wings, this man has some to offer – there is no doubt.