Born in 1939, Reiner Stemme studied mechanical engineering and physics at the Universities of Berlin and Berne, and received a doctorate in Laser-Physics. Following his engineering education, he acquired business experience at LasAG from 1970 to 1976, responsible for manufacturing and sales. Dr. Stemme then initiated and managed VDI Technology Center in Dusseldorf and Berlin until 1985. In this role, he allocated resources and monitored the performance of technology start-ups in a wide range of fields.
An accomplished sailplane pilot, Dr. Stemme grew up intrigued by Hirth's 1930's dream of convenient recreational travel by cross-country soaring safari. To fulfill that vision, however, imposed the challenge of creating one airplane that could combine practical power flying and high performance soaring.Over decades, he watched other members of the soaring community explore potential solutions. Solutions generally fell into two categories: Either modify a traditional powered plane by extending the wings, or add a small engine to a sailplane.
Breakthrough Design Concept
After years of thought, Dr. Stemme conceived and patented a breakthrough solution to fulfill Hirth's dream. Rather than move the engine or propeller, a unique folding propeller is driven by an engine mounted mid-ship using a drive shaft.This breakthrough configuration permitted, for the first time, an aerodynamically clean fuselage during soaring flight and instant access to the power of a full-sized, four-stroke aircraft engine. Leaving the security of conventional business, Dr. Stemme founded Stemme GmbH & Co.KG in 1985 to bring his new design to reality.
Propulsion System Development
In 1985, work began on the airframe design and proof of concept prototype. The novel propulsion system worked well during ground tests, but the design team held their breath on the first flight.A s experienced engineers, they knew theory and real-world practice are sometimes different. They knew the first flight would confirm or disprove the merits of the revolutionary Stemme design.
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Stemme turned to the world renown team of Horstmann and Quast to meet these design challenges. Working in Braunscheig at the German Center of Aviation and Space Technologies, their effort resulted in the HQ41 advanced laminar airfoil.In all respects, the new airfoil met Stemme's design requirements as evidenced by the plane's performance characteristics: Spin resistant stall, 50:1 L/D, 110 fpm minimum sink rate (only 200 fpm at 90 kts) and a remarkable 4.5 seconds per 90 degrees of roll.
Powered by a normally aspirated Limbach 93hp four cylinder, four stroke engine, a new class of self-launching sailplane was born with European LBA certification of the Stemme S10 on September 31, 1990. Operating with the ease of a power plane and the performance of a high performance sailplane, Hirth's dream of soaring with complete independence had finally become a reality. The Stemme S10 rapidly became associated with its moniker, The Best of Both Worlds.
Stemme embarked on a program to certify the airplane in the U.S, resulting in FAA type certification in June, 1992. The U.S. version, named Chrysalis after the miraculous transformation between caterpillar and butterfly, incorporated a modified fuel system and numerous other changes to meet certification requirements.
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The Variable Pitch Propeller: Meeting a Need for Speed
True to Hirth's vision, Stemme S10 owners quickly learned to exploit the plane's unique capabilities.Solo safaris over long distances became commonplace.
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To further serve this need for long and fast distance capability, Stemme engineered a further refinement to the folding propeller -- An ability to thermoelectrically select between two pitch settings: Takeoff and cruise.Cruise speed went up from 90 kts to 120 kts and takeoff/climb performance improved markedly. Type certification was awarded in September 1994. The S10-V was born!
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So Dr. Stemme embarked on the ultimate refinement of the drive concept: Turbo-charging. Rather than retrofit a turbocharger to an existing power plant, the decision was made to incorporate the new and highly regarded Bombardier-Rotax turbo-charger 914 aircraft engine. Entering service with an initial TBO of 1,000 hours, the engine provides 115 horsepower up to 12,000 feet msl. As a result, cruise speed increased to 140 kts, climb rate at 10,000 feet is a remarkable 800 feet per minute and service ceiling is over 30,000 feet msl. Changes in the certification procedures and requirements required a massive re-certification effort throughout 1996 resulting in issuance of a new type certificate to the S10-VT Turbo at the 1997 National Business Aviation Convention.
Not all development effort, however, was lavished on improvements to powered flight.
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With demand setting new records, Stemme sought and received an additional infusion of capital in 1997 to expand its manufacturing capacity. New offices were acquired at Strausberg, an airfield 20 miles East of Berlin and construction of new production and development facilities began in the fall. As a result, the company is well positioned to pursue its growth plans for the future.
Entering 1998, the company's primary focus is expansion of its manufacturing capacity and customer support capability for the S10 family of aircraft.Stemme is committed to providing technical and maintenance support to its growing number of customers on a par with its world class aircraft.
In response to considerable demand for special purpose aircraft for surveillance, reconnaissance, remote sensing and environmental survey, Stemme announced the S15 Utility model. Underwing hard attach points carry mission specific payloads weighing up to 140 lbs (65 kg) each. Forward Looking Infra Red (FLIR), night sun search lights and video cameras are available for law enforcement, border patrol and environmental monitoring applications. Teamed with Wescam, the leading supplier of stabilized airborne camera equipment, the S15 Utility can provide broadcast quality video coverage. Infrared fire detection equipment can serve forestry management needs. In each case, the S15 Utility can loiter at low altitudes in tight circles – serving many of the observation roles performed by helicopters at a small fraction of the cost.
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Stemme continues to perform aerodynamics studies for the DLR (German equivalent to NASA). For example, in 1997 an S10 equipped with micro spoilers helped better understand the fluid dynamics of bird wings at high angles of attack. The research confirmed the micro spoilers significantly reduced reverse air flow -- important results which may be applied to large transport aircraft.
Considerable private and public interest is focused on Unpiloted Air Vehicles (UAV's) for a variety of missions. The S10's high performance laminar airfoil, high aspect ratio composite wing structures and revolutionary drive system is appealing to UAV system integrators. Stemme supplies airframe and propulsion components under its S-UAV program.
The modular design of the S-10 Family lends itself to modification and adaptation. Dr. Stemme and his talented team are sure to continue expanding their unique family of aircraft. Visit the company's website periodically at www.Stemme.de to receive future announcements.
