Gliding is probably the closest one can get to truly flying like the birds and by birds, I mean eagles and other raptors that have mastered the art of using thermals to their advantage. The one drawback is that one usually needs a tow-plane or a winch to get airborne. The Stemme S12 makes it possible to enjoy the silent world of soaring form almost any airfield without assistance.
The Stemme S12 is an evolution of the earlier S10, which in itself is a very impressive aircraft. The Stemme S12 carries many of the S10 features like the cantilever wing, T-tail, a two-seat side-by-side configuration enclosed cockpit under a bubble canopy and a single engine with a retractable propeller.
The aircraft is made from predominately composite material with a mid-fuselage-mounted Rotax 914 F2/S1 four-stroke turbocharged engine that delivers 115 hp to a foldable variable pitch propeller via a drive-shaft neatly concealed in the centre-tunnel-fairing. The propeller completely disappears into the propeller dome when not in use ensuring that no propeller drag is experienced.
The engine doubles for the take-off power that frees the pilot from the need of a ground crew or even a tow-plane. To start the propeller, the dome slides out and the propeller blades unfold. It takes just 5 seconds to convert from glide mode to engine mode preventing the need for out-landings when no lift can be found.
“With the S12 we have further refined the original Stemme idea and offer pilots two complete aircraft in one,” said Paul Masschelein, CEO of Stemme AG. “The S12 delivers the comfortable travel of a powered aircraft along with the pure adventure of gliding. Many intensive discussions with powered and glider pilots alike show us that with the Twin Voyager we have exactly met the needs of many pilots.”
The most impressive feature of the Stemme S12 must be the new wing design, the 25-meter wingspan with new wing geometry, that includes more dihedral near the wingtips, a glide ratio of 53:1 has been achieved compare this to a thoroughbred 18m competition glider with a 50:1 glide ratio and one gets an idea of how well this machine performs.
For those people that enjoy a spot of touring a baggage compartment is integrated into the fuselage providing space for hand luggage up to 22kg, more than ample for a change of clothes and the necessary toiletries. The centre-tunnel-fairing provides additional storage space for your smart-phone, notebook and other onboard companions.
In the tradition of making certain, the Stemme motor glider can be handled by one person alone, the wings of the S12 fold backwards toward the tail after a bit of unfastening work the S12 then fit into a standard 12-meter T-hangar.
Optional avionics in the S12 includes an LX soaring computer with eVario, a nifty device that helps the pilot locate and remain inside those invisible thermals needed to remain aloft. An AHRS can also be added to the Dynon EFIS-D10A display. Other options include a Garmin GPS, a Mode S transponder, a compass and a Flarm, a device that functions like a TCAS to point out other similarly equipped soaring aircraft nearby. An autopilot and innovative electrical trim equipment is also part of the richly equipped cockpit.
The Stemme Twin Voyager S12 offers the pilot the best of both worlds all in one aircraft.
General characteristics
Crew: one
Capacity: one passenger
Length: 8.42m (propeller retracted)
Wingspan: 25m - 11.4 m span when folded
Height: 1.75m
Wing area: 19.95m²
Aspect ratio: 31.33
Gross weight: 900kg MTOW
Fuel capacity: 120 litres
Powerplant: 1 × Rotax 914 F2/S1 four-cylinder, liquid and air-cooled, turbocharged, four-stroke aircraft engine, 115 hp
Propellers:two-bladed retractable, folding, variable-pitch propeller
Performance
Maximum speed: 140kn at 10,000 feet MSL
Cruise speed: 120kn
Range: 950nmi
Endurance: 9.2hr @ 55% power
Maximum glide ratio: 53:1
Rate of climb: 4.21m/s or 829ft/min
Wing loading: 45.11kg/m² at MTOW
