MD80S ACFT DURING PREFLT REVEALED AN APPARENT IMPROPER REPAIR OF THE #2 ENG INTAKE LINING. POSSIBLE UNAUTH MATERIAL WAS USED FOR REPAIR AND THE REPAIR WASN'T IN THE ACFT LOGBOOK.

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ON THE EXTERIOR INSPECTION; WE DISCOVERED AN APPARENT PREVIOUS REPAIR AND SUBSEQUENT DAMAGE TO #2 ENG INTAKE DYNAROHR LINING AT THE 12 O'CLOCK POS. FROM THE GND; AN APPROX 2 SQUARE FT AREA APPEARED WRINKLED WITH A CRACK ALONG THE FORWARD RIVET LINE. CONTRACT MAINT WAS CALLED AND THE MECH DISCOVERED THAT THE INTAKE HAD INDEED BEEN PREVIOUSLY REPAIRED BUT WITH AN ELASTIC; RUBBERY COMPOUND THAT HE SAID WAS NO LONGER AUTH FOR INTAKE REPAIR WORK. THE REPAIR HAD COME LOOSE ALONG THE FORWARD EDGE AND THE AIRFLOW HAD FORCED ITS WAY UNDER THE REPAIR AREA AND HAD THEN DELAMINATED THE METAL SURFACE OF THE LINING FROM THE HONEYCOMB BASE; FROM THE BEGINNING OF THE INTAKE TOWARDS THE AFT; ALMOST TO THE REAR OF THE LINING. THE LINING APPEARED TO BE READY TO SEPARATE AND IF THIS WERE TO HAPPEN INFLT WOULD HAVE SEVERELY DAMAGED THE ENG AND PROBABLY WOULD HAVE RESULTED IN AN INFLT ENG FAILURE OR SHUTDOWN. REVIEW OF THE ACFT DAMAGE LOG SHOWED NO PREVIOUS REPAIR WORK NOTED FOR THE #2 ENG INTAKE. IN SUMMARY: 2 THINGS CONCERN ME: 1) WAS THE PREVIOUS REPAIR WORK DONE UTILIZING UNAUTH MATERIALS? 2) WHY WAS THERE NO INDICATION OF REPAIR WORK INDICATED IN THE ACFT DAMAGE LOG?