KLM Royal Dutch Airlines

AD Notice of Proposed Rulemarking (NPRM) comment for nonconforming No. 3 bearing packings. KLM uses an alternate means of N2 system vibration reduction called out the core trim balance procedure approved per KLM Engineering Authorisation under the authority of DOA No. EASA.21J.012 with reference to GE Customer Departure Record GM-10-0021. This procedure gives us the opportunity to restore the on-wing N2 vibration complaints per off-wing limited workscope. This means that weights can be put on either the high pressure compressor rotor or the high pressure turbine rotor per Engine Manual assembly procedure to reduce the N2 unbalance. The high pressure compressor rotor can be balanced according a high pressure compressor top case removal. The high pressure turbine rotor can be balanced by putting balance cups at the aft side of the HPT stage 2 Disk. Therefore we have to remove the low pressure turbine module to get access to the high pressure turbine rotor. KLM would like to see an additional exception to paragraph (g) “Definition” to perform the core trim balance procedure where the separation of a major engine flange occurs.