After blades are removed from the hub, they are thoroughly cleaned prior to initial assessment. Ninety-five percent of blades are processed through the Aeroscan machine to confirm they are within minimum dimensions and that there is enough material left to go through the overhaul process. A water jet machine is used to blast the lead ballast out of the balance hole. Blades are then stripped for further visual inspection and dimensional inspection of the shank and bore. Bent blades are returned to shape, and all damage and corrosion is removed from the blade by sanding. Blades are dimensionally checked again for minimum widths and thicknesses.
Set Matching: Blades may track within each other in a set; however, due to thrust bending, most blades require correction to their face alignment to bring it back to manufacturers’ limits. Blades are twisted and straightened as required to adjust face alignment and angles to within manufacturers’ tolerances. After face alignment and angles are corrected, trailing edges are filed as required to match edge alignment. After edge alignment is matched, leading edges are filed to match as a set. This unique attention to detail during the overhaul process can add a couple of extra hours of labour to the process. For the owner, the passengers and the aircraft itself, however, the benefit of set-matching is a smoother spinning propeller and an overall reduction in vibration. Blades are processed through the Aeroscan machine for recording of final airfoil dimensions.
Hamilton Standard blade thrust washers are ground as required and magnetic-particle inspected. Blades are further inspected by optical comparator, etching, borescope inspection, liquid penetrant inspection, eddy current inspection, and ultrasonic inspection as required. Blades are cold rolled, polished, shot peened, alodined, and anodized as required before being painted. Finished blades are primed, painted, statically balanced and inspected prior to installation assembly.
Blades begin with a thorough visual inspection and assessment – including an internal fibre-optic borescope inspection to determine serviceability. Protective coatings are removed as required. Fibreglass, carbon fibre and foam repairs are carried out. Delaminations are repaired using vacuum bag repair. Leading edges are replaced as required. Blades are sanded as required using our state-of-the-art dust collection system. They are then further inspected by tap test, optical comparator, etching, liquid penetrant inspection, eddy current inspection, magnetic particle inspection and ultrasonic inspection as needs dictate. Blade shanks are cold rolled, shot peened and alodined as required. Finished blades are then primed, painted, statically balanced and inspected prior to installation assembly.