On the heels of a Service Bulletin, the FAA has issued Airworthiness Directive 2007-26-12 focusing on Robinson R22 and R44 main rotor blade delamination.
The AD notes that main rotor blade skins begin to debond at the skin-to-spar bond line on the lower surface near the blade tip. Debonding can occur when the bond line is exposed due to excessive erosion of the blade finish or when corrosion attacks
the internal aluminum tip cap.
Compounding the problem, the blades are matched and balanced at the factory,
so if one blade is due to be fixed or replaced ($16,432 for each Model R22 blade, and about $23,060 for each Model R44 blade), it is likely the opposite blade will also need replacing.