German research body DLR studies wing-contamination by insects

German aerospace research centre DLR is conducting test flights to assess how wing contamination by insects can be avoided on laminar-flow aerofoils.

While the aerodynamic efficiency of conventional wings is not significantly compromised by collection of insects, the super-smooth surfaces of laminar-flow aerofoils will not tolerate such contamination.

The efficiency gains of such novel wing designs will depend on a perfect, uninterrupted airflow in the boundary air layer close to the aerofoil’s surface. But insects on the leading edges will cause turbulences in that boundary layer.

Aerodynamicists at DLR are planning to install retractable Kruger wing flaps on laminar-flow wings, which would both redirect insects away from the leading edges and serve as lift-enhancing slats during take-off and landing.

Now, the institute is conducting test flights with its Airbus A320-based “Advanced Technology Research Aircraft” to determine how much wings are contaminated by insects with conventional slat configurations.

With sections of the aircraft’s wing leading edges have been covered with adhesive plastic sheets, the twinjet is conducting low passes at Magdeburg Cochstedt airport at a height of approximately 50ft.

The sheets are subsequently removed and scanned to measure contamination levels during different phases of flight.

That data will be used to calibrate and further develop aerodynamic computer models, says DLR. This will help in determining the size of the Kruger flaps, which should be kept to a minimum size to ensure adequate shielding against insects and sufficient lift for the take-off and landing phases.

DLR adds that it used the test campaign at Magdeburg airport also to trial its newly developed guidance system that should help pilots to better follow descent profiles for landing. This is part of project dubbed as “energy-based pilot support system for precise adherence to vertical approach flight profiles”.

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