Summary
The FAA proposes to adopt a new airworthiness directive (AD) for Rolls-Royce Deutschland Ltd & Co KG (RRD) (formerly Rolls-Royce plc) Dart 528-7E, 529-7H, -7E, -8E, -8H, -8X, -8Y, -8Z, 529D-7E, -7H, -8E, -8H, -8X, -8Y, -8Z, 531, 532-2L, -7, -7N, -7P, -7L, -7R, 535-2, -7R, 542-4, -4K, -10, -10J, -10K, 552-2, 552-7, and -7R turboprop engines. This proposed AD would require removal of any Sermetel coating (Omat 7/46) from certain high pressure (HP) turbine discs and intermediate pressure (IP) turbine discs, and inspection of discs after coating removal. This proposed AD is prompted by reports of Sermetel coating (Omat 7/46) applied to certain turbine discs which, if allowed to remain on the discs would react adversely with the disc dry film lubricant, and could result in uncontained HP or IP turbine disc failure, resulting in possible damage to the airplane. The actions specified in this proposed AD are intended to prevent uncontained HP or IP turbine disc failure, which could result in damage to the airplane.