fs35 – Harpyie

Efficient, Simple, Powerful

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It’s practical to have a tow plane. This rule applies for every flying club as one then has an alternative to winch launches. Furthermore, aerotow takeoffs allow pilots to start from a higher altitude, which has its benefits as well.

Since the Akaflieg Stuttgart has built several sailplanes with a multitude of different designs, it was decided to take on a new challenge: a motorized plane. First things first though, it was necessary to set our goal for the plane. We wanted a plane that can quickly and cheaply tow our sailplanes, meaning a plane that is optimized for climb performance.

All the factors that affected climb along with ways to keep costs for aerotows down were quickly examined, and this led to the following design:

The fs35 is a two-seater touring motor glider with a side-by-side seating arrangement and a MTOW of 850 kg. Weight was an important factor as it had a major effect on climb. The seating arrangement was no accident, such a configuration made introducing and training new pilots on the fs35 easier. This was further simplified by the ergonomic layout of the cockpit, allowing for straightforward operation of the plane. The wings of the aircraft were optimized for climb performance, as per the goal of the project. On the flipside, the fs35 is equipped with a relatively large fuel tank. While this may seem counterproductive, having a large fuel reserve allows for multiple takeoffs before needing to refuel.

On the 13th of August 2019, the fs35 finally took to the skies. In short, the plane met all our expectations and then some, being easy to fly and climbing like a rocket. We hope to be able to operate the fs35 in our regular flight operations soon!


First flight13 August 2019
Construction methodCRP-Sandwich
Wingspan17,67 m
Wing area16,9 m²
Aspect ratio18,5
ProfileFX 63-K-137 (mod)
Dihedral angle
Aileron area 
Wing planformTrapezoidal
Length7,5 m
Heightca. 2,7 m
Empty weight669 kg
MTOW850 kg
PowerplantContinental CD-155 with 155 hp
UndercarriageTricycle undercarriage
PropellerMT 3-bladed hydraulic
Cruise speed220 km/h
Max speed270 km/h
Max climb performance with a single
seater sailplane in tow
4,7 m