Everybody who is addicted to fly would like to be able to go flying whenever he wants to.

But: With normal motorized airplanes you have emission of exhaust gases as well as noise that often results in discussion with neighbours.

On the other hand there are sailplanes which do not cause this disturbances, but you need someone to bring you into the air, even by winch or by aircraft towing. You have also secure to have enough fuel at the airfield.


A solution to satisfy the needs of the pilots as well as nature and neighbours could be a motorized glider powered by solar and battery power.


The aim of this project is the construction and building of a solar motor glider as amateur project in the 120Kg / FAR103 class.



During the last 20 years several solar aircrafts had been developed. Most of them had been done by research teams at universities or as big project covered by industrial sponsors.

1980: Pathfinder 1980 / 1996: Solair I + II

1989 / 2006: Sunseeker I + II 2004 / 2009: Solar Impulse I + II


Project description:

Since a few years a class of light sport aircrafts with a maximum empty weight of 120Kg has been defined. Similar to the FAR 103 it allows flying for pilots with low requirements and costs compared to standard ultra light air sailplanes:

- no medical which has to be renewed periodically

- in general slow and easy handing of the aircrafts

- maintenance and repair in own responsibility

- lifetime licence

Sunseeker II that has been build more than 10 years ago already fulfils these requirements.

Requirements for new development:

- maximum empty weight 120Kg (incl. battery)

- folding propeller in the back of the glider

- Capable to start independently on grass runways

⟹ usable on many ultralight and gliding airfields

- charging of onboard battery using solar cells placed on the wings and aileron

- easy assemble and disassemble of the glider by one person

- enough power from the solar-engine-propeller unit to allow evelflight by

sunpower only. So a limitless flight is possible as long as the sun is shining.


Name Horos:

Horos has been one of the main gods in the early Egypt mythology. Originally he

has been the god of the sky and also the king of gods, light and universe as well

as a guardian for children.



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Solarflugzeug Solarflieger Solar Flugzeug Flieger Michael Behn

Alatus M

Alatus M, 120Kg UL-Motorglider

Horos: Design for aerodynamic analysis

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Dipl. Ing. Michael Behn