Twin Voyager S12 is a new model two-seat motor glider under development by Stemme, a German manufacturer located near Berlin.

In 2015, Stemme presented the prototype of S12 at the AERO Friedrichshafen, Europe’s most important aviation exhibition. The European Aviation Safety Agency (EASA) granted type certification for the Twin Voyager S12 in March 2016. The S12 was also going to be validated by the US Federal Aviation Administration (FAA).

Developed to target pilots and flying enthusiasts, the aircraft can be converted from glider to motorised plane in just five seconds. Stemme had more than 20 orders in hand for Twin Voyager S12 in 2016.

Stemme Twin Voyager S12 design and features

As an evolution of the S10 Motor Glider, the Stemme Twin Voyager S12 has a separate baggage compartment integrated into the fuselage. By providing space for hand luggage, the compartment significantly expands touring options. With its 25m wingspan, the high-performance glider achieves a glide ratio of up to 53.

The retractable undercarriage has a wheelbase of 1,360mm, which grants more stability in ground handling.

The Stemme S12 has an overall length of 8.42m (27.6ft), height of 1.75m (5.74ft) and wingspan of 25m (82.02ft). The wing area is 19.95m² (214.74ft²) and the wingspan can be reduced to 11.4m (37.40ft) when folded.

Cockpit and avionics

The solid and safe one-piece canopy offers great panoramic views. The side-by-side alignment is ideal for sharing workloads, using the same avionics or simply for pure recreation, just as in conventional planes. The centre-tunnel-fairing provides additional storage space for smartphones, notebooks or other on-board companions.

A Dynon autopilot is part of the well-equipped cockpit. In disconnected mode, it provides an extremely direct steering feeling, which is immediate and sensitive.

“The aircraft is further equipped with an LX soaring computer, including e-Vario, and an altitude and heading reference system (AHRS) with stick remote control.”

The aircraft is further equipped with an LX soaring computer, including e-Vario, and an altitude and heading reference system (AHRS) with stick remote control.

Its avionics features include a compass, altimeter, ELT 406 MHz, Garmin GPS, mode-S transponder with ADS-B out and ADS-B in, traffic sensor, and fuel computer. Other avionics equipment includes acoustic stall warning, fire warning systems and classic UMA engine instrumentation.

Engine and performance details

The unique folding propeller that disappears completely into the dome during glide mode gives the aircraft excellent aerodynamics, while the powerful ROTAX 914 F2/S1 Turbo engine gives pilots uncompromising travel performance.

The engine is behind the cockpit and drives the propeller through clutch assembly and a carbon fibre driveshaft, which inflicts no penalty on the Stemme’s gliding and soaring performance.

The aircraft has a fuel capacity of 120l (31.7gal) and fuel consumption of 13l/h (3.4gal/h).

The maximum cruise speed is 259km/h (140k) at an altitude of 10,000ft. The maximum range of the aircraft is 1,759km (950nm) with a climb rate of 4.21m/s (830ft/min), and the maximum take-off weight is 900kg (1,984lb).