Durability of hybrid laminar flow control (HLFC) surfaces

As a part of the European Commission sponsored HYLTEC (Hybrid Laminar Flow Technology) project, a SAAB 2000 aircraft - fitted with a number of small laser drilled panels on the wing leading edge - completed 20 months of routine service; the objective being to investigate contamination and durability aspects of Hybrid Laminar Flow Control (HLFC) suction surfaces. A post-flight test investigation of these panels, manufactured from Nd-YAG laser drilled titanium, aluminium and carbon fibre polyetheretherketone (PEEK) composite, has been conducted. Using Scanning Electron Microscopy (SEM), evidence of corrosion and damage was investigated. An optical inspection technique was used to measure hole geometries and the results were compared to pressure loss measurements through the panels. Titanium was found to be the most robust material, displaying no adverse affect from this exposure, whilst aluminium was found to be substantially less durable. The PEEK carbon fibre composite showed signs of surface degradation after only two months of flight trials.