TO: SENSENICH DISTRIBUTORS, FAA APROVED REPAIR STATIONS, PIPER CHEROKEE OWNERS AIRCRAFT MODELS AFFECTED: PIPER CHEROKEE PA-28-160 ONLY WITH S/N 28-671 TO 28-2336 lNCLUSIVE

COMPLIANCE DATE: PRIOR TO BUT NOT LATER THAN NEXT 20 HOURS OF OPERATION

SUBJECT: INSPECTION OF MID-BLADE AREA OF MT6EMM AND M76EMMS PROPELLERS

Sensenich Propeller Bulletin No. R-10 dated 4 January 1965, required the removal of the mid-blade decal so that the area under and adjacent to the decal could be examined for corrosion pits. These corrosion pits had, in some cases, initiated a fatigue crack which resulted in a failure of the propeller blade. These corrosion pits are clusters of tiny black dots (see sketch #1) which appear most frequently under the narrow black border of the decal.

It now appears that some owners, when attempting to comply with Bulletin R-10, were looking for a white powdery corrosion and failed to notice the small black dots. The new style epoxy adhesive decal was then installed over these corrosion pits. For this reason, and to ensure that all propellers are properly inspected, the mid-blade decals must be removed. The decals should be soaked with paint remover and rubbed off with a rag; they must not be scraped or sanded off. The mid-blade area (sketch #2) must be thoroughly re-inspected with a glass of approximately 3 power.

It a crack is found, the propeller must be replaced immediately. If corrosion pits (the tiny black dots) are discovered they must be removed within the next 20 hours of operation. They can be removed in the following manner: (1) Sand the area with 220 grit wet-or-dry abrasive paper and polish with 320 grit or finer. (2) Clean the area thoroughly and apply a dye penetrant. (3) Inspect with a low-power glass; it is very important that the bottom of the pits be completely removed. If the pits re-appear, repeat the operations. (4) When the pits are completely removed, spray the area with a clear lacquer.

Owners who wish to do so may return their propellers to the factory for reconditioning or exchange for a factory reconditioned propeller.

NOTE: This bulletin does not apply to propellers which have been reconditioned or exchanged by the factory in compliance with Bulletin R-10.

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