A FALSE CARGO DOOR WARNING REQUIRED THE ACFT TO RETURN LAND.

Narrative

THERE ARE RECURRING INCIDENTS OF FALSE 'DOOR OPEN' WARNING LIGHTS ON OUR MD82-MD83'S. THIS IS APPARENTLY DUE TO DOOR MISALIGNMENT OR SHIFTING OF THE DOOR DURING TURB OR JARRING ON ROUGH RWYS LIKE SAN JOSE; CA. DURING ROTATION AND LIFTOFF; WE RECEIVED AN AFT CARGO DOOR OPEN ANNUNCIATION LIGHT. THE CABIN ALT WAS INCREASING. DUE TO CONCERNS OF PRESSURIZATION CAPABILITY;WE DECIDED TO RETURN TO LAND. THE SUBSEQUENT LNDG WAS NORMAL. INSPECTION BY RAMP PERSONNEL (NOT MECHS) SHOWED THE DOOR TO BE CLOSED. THE DOOR OPEN ANNUNCIATOR SYS APPEARED TO BE WORKING PROPERLY (EACH CARGO DOOR WAS OPENED AND CLOSED REPEATEDLY). MY DECISION WAS THAT NO MAINT WAS REQUIRED. THEREFORE NO MAINT LOG ENTRY WAS MADE. AFTER REFUELING; THE FLT CONTINUED NORMALLY WITH NO FURTHER DOOR OPEN WARNING LIGHTS. IT SEEMS THAT A DIFFERENT DESIGN FOR DOOR OPEN INDICATION SENSING IS NECESSARY TO PREVENT THIS RECURRING SCENARIO FROM HAPPENING. THIS IS MY 4TH EXPERIENCE IN 4000 HRS WITH THIS SAME PROB. MANY OTHERS HAVE OCCURRED TO OTHER PLTS IN OUR COMPANY ALONE. PROBABLY AN INDUSTRY-WIDE PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS AN INSTRUCTOR PLT WITH AN ACR THAT OPERATES A MEDIUM SIZED FLEET OF MD-80 ACFT. THIS ANALYST IS RETIRED FROM A MAJOR ACR THAT OPERATES AN EXTREMELY LARGE FLEET OF MD-80 ACFT. THE RPTR AND THE ANALYST TALKED ABOUT THIS PROB AND THE FACT THAT THE ANALYST HAS NEVER HEARD OF THIS PROB BEFORE; EITHER WITHIN HIS FORMER ACR OR ANY OTHER ACR. THE CONCLUSION IS THAT MAYBE THE RPTR'S ACR HAS A UNIQUE PROB. THE RPTR WAS INSTRUMENTAL IN GETTING A NEW PROC ON HIS ACR'S CHKLIST FOR THIS PROB. THE SENSING DEVICE IS A 'PROX SWITCH.' THE SOLUTION FOR THE GND PERSONNEL IS TO SLAM THE CARGO DOORS HARDER; WHICH OF COURSE IS NO SOLUTION AT ALL. THE RPTR WAS COUNSELED TO HAVE HIS PEOPLE CONTACT THE VERY LARGE OPERATOR OF MD-80 ACFT AND SEE IF THEY HAVE FOUND A SOLUTION TO THIS PROB.