Rain Repellency for Shipboard Aircraft Transparency

Navy aircraft often have to taxi, take-off, and land during conditions of differing amounts of rain. While performing taxi and take-off operations the pilot must be able to clearly see ground crew directions. During landing, the pilot must be able to clearly see landing strip lights, and for carrier landings, the Optical Landing System (OLS). As a consequence, maintaining visibility during inclement weather is critical to flight crew operations. This can be a difficult task as aircraft transparency materials are not inherently water repellent and there are no mechanical means of maintaining viability. To address this issue, the Navy is interested in the development of innovative methods to promote water shedding during ground and low speed operations. Under the proposed program, METSS will address this issue by using a proprietary process to permanently treat the surface of existing aircraft transparency topcoat materials with an appropriate level of short chain hydrophobic polymers to create a highly rain repellent surface. The hydrophobic materials will remain permanently anchored into the surface of the topcoat via polymer chain entanglement networks or, alternatively, cross-linked into the polyurethane coating, essentially forming an interpenetrating polymer network (IPN). The significant advantage of the proposed process is that the bulk properties of the aircraft transparency topcoat will not be measurably altered by the surface treatment process as the amount of materials infused into the surface of the topcoat will be quantified at molecular levels. Critical performance testing will be conducted to demonstrate rain repellency while maintaining strict adherence to optical property requirements and service life performance in an aggressive marine aviation environment.