Surface Contamination Effects on CRM Wing Section Model

The aerodynamic effects of Cold Soaked Fuel Frost have become increasingly significant as aircraft manufacturers have applied for to allow it during aircraft take-off. The Federal Aviation Administration and the Finnish Transport Safety Agency signed a Research Agreement in aircraft icing research in 2015 and started a research co-operation in frost formation studies, computational fluid dynamics for ground de/anti-icing fluids, and de/anti-icing fluids aerodynamic characteristics. The main effort has been so far on the formation and effects of CSFF. To investigate the effects a HL-CRM wing wind tunnel model, representing the wing of a modern jet aircraft, was built including a wing tank cooling system. Real frost was generated on the wing in a wind tunnel test section and the frost thickness was measured with an Elcometer gauge. Frost surface geometry was measured with laser scanning and photogrammetry. The aerodynamic effect of the frost was studied in a simulated aircraft take-off sequence, in which the speed was accelerated to a typical rotation speed and the wing model was then rotated to an angle of attack used at initial climb. Time histories of the lift coefficient were measured with a force balance. Time histories of the upper surface boundary layer displacement thickness were measured with a boundary layer rake. For comparison the effects of typical anti-icing fluids, sandpaper and smooth PVC plastic sheet were also measured. The lift losses correlated with average surface contamination roughness height and the boundary layer displacement thickness increment.