TOTAL OF 4 B757-200 ACFT MAY HAVE INCURRED PYLON STRUCTURAL DAMAGE DURING ACCOMPLISHMENT OF AN ENGINEERING CHANGE ORDER.

Narrative

DURING SHIM REMOVAL FROM THE FIRST DAY; WE WERE USING A G-8 TO HAMMER OUT SHIMS; AND DRIVING WEDGES UP IN THE CASTERS AS FAR AS IT WOULD GO (TITANIUM) THEN BEAT THE WEDGE OUT. I THINK DAMAGE AND UNDUE STRESS HAVE OCCURRED BUT TO WHAT EXTENT IS UNKNOWN BECAUSE OF ACCESSIBILITY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ENGINEERING CHANGE ORDER REQUIRED A CHK OF THE MID BULKHEAD ALUMINUM SHIMS TO CHK FOR MIGRATION. THE RPTR SAID IF MIGRATION WAS FOUND; THE SHIMS MUST BE REPLACED WITH STAINLESS STEEL SHIMS. THE RPTR STATED THE ENGINEERING CHANGE ORDER REQUIRED USE OF A LARGE RIVET GUN TO DRIVE A TITANIUM WEDGE BTWN THE BULKHEAD AND THE ENG MOUNT FORGING THUS CREATING A GAP TO ALLOW THE ALUMINUM SHIM TO BE REMOVED. THE RPTR SAID THE JOB REQUIRED 3 DAYS WITH ALL 3 SHIFTS FOR EACH PYLON AND WHEN DRIVING THE TITANIUM WEDGES IT WOULD CUT INTO THE SURFACE METAL OF THE BULKHEAD CREATING UNSEEN DAMAGE. THE RPTR STATED AFTER 4 AIRPLANES HAD THE CHANGE ORDER COMPLETED; THE CHANGE ORDER WAS STOPPED DUE TO POSSIBLE STRUCTURAL PYLON DAMAGE. THE RPTR STATED THE 4 AIRPLANES WILL BE ROUTED BACK AGAIN FOR INSPECTION.