75-12-04 ROCKWELL INTERNATIONAL: Amendment 39-2231. Applies to Sabreliner Model NA 265-40 airplanes, serial numbers 282-112, -113, -115 through -137, and model NA 265-60 airplanes, serial numbers 306-64 through -102, certificated in all categories.
To prevent possible failure of engine supports due to cracks in the engine support beams outer skins, accomplish the following:
(a) Within the next 10 hours' time in service after receipt of this airmail letter, unless already accomplished, perform a close visual inspection of the R.H. and L.H. engine support beam outer skin (Ref: 40/60, IPC NA 62-1208, Chapter 17, Page 14, Item 6) for cracks. If cracks are found, either:
(1) Install a doubler type repair per NA 265-40/-60 Structural Repair Manual for issuance of special flight permit per FAR's 21.197 and 21.199 to a base where (2) can be performed; or
(2) Replace the entire outer skin prior to further flight. Replacement of the outer skin constitutes terminating action under this AD.
(b) Within the next 50 hours' time in service after receipt of this airmail letter, unless already accomplished, inspect the R.H. and L.H. engine support beam outer skin by eddy current method for hardness in accordance with Sabreliner Service Bulletin 75-16 dated May 12, 1975, or later FAA-approved revisions. If the material is as required no further action is necessary. If the material is found defective (too hard), compliance is required as follows: For those airplanes having a crack in the engine support beam outer skin, repair and ferry flight only to a base for skin replacement. For those airplanes with no cracks in the engine support beam outer skin, inspect for cracks at intervals not to exceed 100 hours' time in service from the time of the first eddy current inspection using the dye penetrant method in accordance with Sabreliner Service Bulletin 75-16 dated May 12, 1975, or later FAA-approved revisions until the defective skin is replaced. Replacementof defective skin must be accomplished no later than 650 hours' time in service after receipt of this airmail letter and is considered terminating action.
(c) Equivalent inspections and repairs may be approved by the Chief, Aircraft Engineering Division, FAA Western Region, upon submission of adequate substantiating data.
This amendment becomes effective June 9, 1975 for all persons except those to whom it was made effective by individual airmail letters, dated May 13, 1975 which contained this amendment.