AN A36'S ENG COWLING OPENED BUT REMAINED ATTACHED AT CRUISE. THE PLT RETURN TO LAND AND DISCOVERED A CHAFE STRIP IN THE REAR ENG COWL LATCH.

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ON CLBOUT; AN S-TURN WAS MADE TO AVOID INCOMING/DSNDING TFC ON A RECIPROCAL HDG. AFTER COMPLETION OF CLB TO 4500 FT MSL; ACFT WAS LEVELING TO CRUISE AND ACCELERATING TO CRUISE SPD; ABOUT 10 NM FROM THE ARPT. AT ABOUT 140 KIAS; THE L ENG COWLING BLEW OPEN AND REMAINED ATTACHED TO THE LONGITUDINAL PIANO HINGE. AFTER VERIFYING THAT ZZZ WAS STILL THE NEAREST PAVED ARPT ON THE GPS; AN IMMEDIATE TURN BACK TO THE ARPT WAS EXECUTED; THE GEAR WAS EXTENDED TO ASSIST WITH THE DSCNT AND PWR MGMNT; PWR WAS REDUCED TO 22/2400; AND MIXTURE FULL RICH. PRIORITY HANDLING INTO THE PATTERN WAS REQUESTED AND THE TWR APPRISED OF THE SITUATION. GS WAS ESTABLISHED TO ENTER A L BASE FOR RWY 27 AT ABOUT 1000 FT AGL; AND THE ACFT WAS CLRED INTO THE PATTERN. ON RPTING L BASE; RWY 27; THE ACFT WAS CLRED TO LAND. TOUCHDOWN OCCURRED ON THE RWY; AND AS SPD REDUCED FOR TURNOFF; THE COWLING CLOSED DOWN. DURING THE DSCNT AND LNDG; THE COWLING HAD REMAINED MOSTLY VERT IN THE PROP SLIPSTREAM. AFTER ENG SHUTDOWN; THE COWLING LATCHES WERE EXAMINED; AND A SMALL STRIP OF COWLING CHAFE STRIP WAS FOUND LODGED IN THE REAR LATCH. AFTER REMOVAL OF THE DEBRIS; AND SEVERAL TEST LATCHING/UNLATCHING SEQUENCES; THE COWLING WAS FOUND TO BE SECURE; AND THE FLT WAS RESUMED WITHOUT INCIDENT. AFTER REVIEW OF THE DEBRIS AND LATCH BY THE A&P/IA BACK IN HOME BASE; IT WAS DETERMINED THAT THE STRIP OF MATERIAL MUST HAVE BROKEN OFF THE COWLING AND BECOME LODGED IN THE LATCH WHEN THE COWLING WAS BEING SECURED. INSPECTION AND REPAIR WAS CONDUCTED AS NECESSARY. CONTRIBUTING FACTORS MAY HAVE BEEN THE EXTREME COLD IN THE ZZZ AREA OVER THE PREVIOUS WEEK; LEADING TO FAILURE OF THE ADHESIVE AND/OR THE STRIP ITSELF; ALLOWING IT TO FALL INTO THE LATCH. IMMEDIATE RETURN TO THE ARPT ALONG WITH MEASURES TO REDUCE AIRSPD AND MAINTAIN AIRSPD AND ACFT CTL WERE FACTORS LEADING TO A SUCCESSFUL CONCLUSION.