Powered by a 200 hp Lycoming piston engine, the single-engine LFU 205 has been in service since 1984 at the Braunschweig (Brunswick) flight facility of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). As the first aircraft of this class with a composite construction, it is used as a development test bed for laminar aerofoil profiles.

The aircraft was developed jointly in the 1960s by DLR and the Leichtflugtechnik-Union (LFU) consortium. The maiden flight took place in 1968. The LFU 205 in service in Brunswick is the prototype of this aircraft and was manufactured as a one-off.

DLR LFU's aerofoil has been modified by installing a so-called "glove" with modern laminar profiles. An on-board measurement system has been incorporated to investigate the changed profile and aerodynamic characteristics resulting from this modification.

On test flights with the LFU 205, DLR scientists measure - amongst other parameters - the pressure distribution and drag on aerofoil profiles. In addition, boundary layer investigations are carried out, aimed at giving further insight into the influence of friction on the aerofoil profile. At the same time, laminar and turbulent flows on the wing, and their transitions, are also investigated using infrared technology. Of particular interest here is the transition from laminar to turbulent flows. These can change, for example, due to fouling of the wing leading edge, caused by insects or icing-up. In this condition, because of vortices and crossflow, a turbulent flow at the aerofoil profile causes a higher viscous drag and hence a higher fuel consumption. The aim here is to maintain laminar flow around the profile over as long a distance as possible, i.e. to prevent vortices and crossflow, so minimising the viscous drag.

Missions - research focus

Amongst others, the following investigations are carried out with the LFU 205:

• Measurements of the pressure distribution and drag on aerofoil profiles.
• Boundary layer investigations measuring the influence of friction on the aerofoil profile.
• Observations of the laminar-turbulent transition using infrared technology.
• Investigations to eliminate the laminar-turbulent transition caused, for example, by fouling around the wing leading edge, due to insects or icing-up. Because of the vortices and crossflow, turbulent flow around an airflow profile causes a higher viscous drag (high fuel consumption). That is why every effort is made to maintain laminar flow around a profile over as long a distance as possible, i.e. to prevent vortices and crossflow, so minimising the viscous drag.