Method for repairing an airfoil surface having an elastomeric protective coating

Abstract

This invention relates to the repair and removal of erosion or impact damage using hand sandable elastomeric coatings on a curved substrate, particularly such surfaces as the leading edge of the airfoil. Specialized applicators and methods of use are also disclosed.

What is claimed is: 
     
         1 . A method of repairing an airfoil surface having an elastomeric protective coating adhered to a portion of said airfoil surface having a plurality of damage cavities caused by sand and water erosion or impact damage comprising: filling said plurality of damage cavities in said elastomeric protective coating with a liquid repair material of elastomeric polyurethane, polyurea or fluoroelastomer having viscosity between a brushable coating up to the viscosity of a flowable caulking compound sufficient to fill said plurality of damage cavities to form filled cavities using a flexible planar applicator capable of conforming to said airfoil surface while being drawn lengthwise along the airfoil surface. 
     
     
         2 . The method of  claim 1  wherein the contact between the airfoil surface and said flexible planar applicator is maintained by applying pressure in the direction of the airfoil surface to fill the damage cavities with the liquid repair material. 
     
     
         3 . The method of  claim 1  further comprising applying a primer coat in the plurality of damage cavities. 
     
     
         4 . The method of  claim 1  wherein said elastomeric polyurethane, polyurea and fluorolastomer composition having a minimum tensile strength of 1000 psi, an elongation at break of at least 100%, and a Shore A hardness of less than 95 A. 
     
     
         5 . The method of  claim 1  wherein said flexible planar applicator is a flat sheet of elastomeric or thermoplastic material of selected thickness to allow it to be deformable around an arcuate surface and stiff enough to spread viscous material smoothly ahead of it when drawn through the viscous material. 
     
     
         6 . The method of  claim 1  further comprising a preliminary step of applying one or more layers of primer coat over any airfoil surface exposed within said damage cavities using a fine brush capable of controlling the primer coat deposition to about 1.0 mm to about 3.0 mm in diameter. 
     
     
         7 . The method of  claim 1  further comprising a preliminary step of applying one or more coats of said elastomeric polyurethane, polyurea or fluoroelastomer to damage cavities using a fine brush capable of controlling the deposition within a range of about 1.0 mm to about 3.0 mm in diameter prior to said filling step.