Rolls-Royce Tay 611-8 engines, installed on Gulfstream IV series business jets, are subject to a European Aviation Safety Agency emergency airworthiness directive until a modification solution is found.
The directives requires the removal of the engines from affected aircraft within 20 flight cycles or within 200 flight cycles after the latest engine shop visit, whichever occurs first.
EASA says: "These engines are known to be installed on, but not limited to, Gulfstream Aerospace G-IV, GIV-SP and GIV-X aeroplanes." Fokker 70s and Fokker 100s are also Tay-engined, but a different variant.
The airworthiness directive says: "A recent quality investigation by Rolls-Royce Deutschland has identified that certain Stage 2 high pressure turbine (HPT) disc spanner retaining nuts did not receive the proper heat treatment after application of silver plating. This condition, if not corrected, could result in a Stage 2 HPT disc failure, possibly leading to release of high energy debris, resulting in damage to the aeroplane and/or injury to occupants. For the reason described above, this Emergency AD requires the removal of the affected engines from service." EASA adds: "This AD is considered to be an interim action, pending availability of approved instructions for corrective action, which would allow these engines to be released to service."