WING DAMAGE WAS DISCOVERED DURING POSTFLT INSPECTION ON A PA-28 ARROW.

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ON APR/TUE/95 I WAS REQUESTED BY A LCL DESIGNATED FAA EXAMINER TO GO OUT AND DO 3 TKOF'S AND LNDGS AND TO FAMILIARIZE HIM WITH THE AIRPLANE'S AVIONICS. I ACCEPTED THE REQUEST. DUE TO TIME CONSTRAINTS I ASKED HIM TO GO OUT AND DO THE PREFLT; HE DID. I WALKED OUT TO THE AIRPLANE (NXXXX) AND ENTERED THE COCKPIT AND SAT IN THE R SEAT. WHILE GETTING INTO THE AIRPLANE I DID NOT LOOK AT THE R WING. MY ATTN WAS FOCUSED ON THE STEP USED TO GAIN ACCESS TO THE WING WALK AREA. THE FAA DESIGNATED EXAMINER AND I TAXIED OUT TO RWY 35 AT THE GROSSE ILE ARPT. HE DID 2 TKOF'S AND LNDGS TO A FULL STOP; I DID 1 TKOF AND LNDG TO A FULL STOP. THE WX THAT DAY WAS VFR AND THERE WAS NO XWIND. ALL 3 LNDGS WERE COMPLETED IN A NORMAL MANNER WITH NO SIDELOADING OR BOUNCING OF THE AIRPLANE. WHILE EXITING THE AIRPLANE AFTER SHUTDOWN I NOTICED A 1 INCH RIP IN THE UPPER SKIN OF THE R WING. THE RIP IS LOCATED ABOVE THE R MAIN GEAR. IT SHOULD ALSO BE NOTED THE L WING SHOWS SIGNS OF STRESS; BUT THIS STRESS WAS CAUSED BY A PREVIOUS INCIDENT EVIDENT BY THE PAINT PATCH WHICH IS LOCATED IN THE EXACT SAME SPOT AS THE DAMAGE TO R WING. IT IS MY PROFESSIONAL OPINION THAT THE DAMAGE CAUSED TO THIS AIRPLANE IS NOT THE FAULT OF MYSELF OR THE EXAMINER. IT IS MY PROFESSIONAL OPINION THAT IF THERE HAD BEEN AN INEXPERIENCED PLT AT THE CTLS WHO HAD MADE A HARD LNDG THE OUTCOME OF THIS DAMAGE WOULD HAVE BEEN MUCH MORE SEVERE. I BELIEVE THE CAUSE OF PROB WAS DUE TO CORROSION; STRESS AND FATIGUE THAT WAS NOT APPARENT THROUGH A NORMAL PREFLT INSPECTION. THIS WAS BROUGHT TO OUR ATTN AFTER ACCESS PANELS WERE REMOVED FROM THE DAMAGED AREA ALLOWING THE MAINT DEPT ACCESS TO INSPECT THE INTERNAL STRUCTURE OF THE WING. THE ONLY THING I CAN THINK OF TO CORRECT THIS PROB IS TO HAVE MORE FREQUENT INSPECTION INTERVALS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: ACFT IS A PA-28 ARROW. MECH INDICATED THAT THE FATIGUE WAS STRESS INDUCED. IN FINAL ANALYSIS; INSURANCE COMPANY PAID FOR THE REPAIR WORK. RPTR BELIEVES THAT HE SAW A PENDING AIRWORTHINESS DIRECTIVE IN EXAMINER'S UPDATE REGARDING INSPECTION FREQ FOR THIS TYPE ACFT. SUPPLEMENTAL INFO FROM ACN 303983: WITHOUT REMOVING INSPECTION PANELS AND LOOKING INSIDE THE WING ON A NORMAL PREFLT THIS PROB COULD NOT HAVE BEEN DETECTED IN MY OPINION.