A B190 IN CLB AT 9000 FT RETURNED TO THE FIELD DUE TO THE L ENG R COWLING RAISED 1 INCH CAUSED BY A LATCH NOT SECURED.

Narrative

UPON CLBOUT FROM PHL THROUGH ABOUT 7000 FT; I LOOKED OUT THE WINDOW AT THE ENG (L) AND NOTICED THAT THE COWLING APPEARED TO BE NOT PROPERLY ATTACHED. IN SHORT ORDER I DECIDED THE BEST THING WOULD BE TO RETURN TO PHL FROM WHERE I DEPARTED. I SLOWED THE ACFT; CALLED ATC AND REQUESTED A HDG BACK TO PHL AND DESCRIBED THE PROB. I DID NOT DECLARE AN EMER. PHL APCH WAS VERY HELPFUL AND IN ABOUT 10 MINS I WAS ON FINAL FOR RWY 27L. DURING PREFLT; NOTHING UNUSUAL WAS NOTICED ABOUT THE COWLINGS. THE MECH LATER DESCRIBED HOW A COWL COULD BE MISATTACHED BY A MAINT PERSON IF CLOSE ATTN WASN'T PAID. ALSO; WHEN THE PLANES WERE NEWER; THE LATCHES HAD A SMALL LINE INSCRIBED ON THEM SO YOU COULD TELL THEY ARE TURNED TO A LATCHED POS. BUT IN MY CASE; THIS WOULDN'T HAVE HELPED BECAUSE THE REAR COWL LATCH HOOKS WERE MISSED DURING THE CLOSING PROC; AND THE LATCHES WERE IN THE CLOSED POS. IT'S TOO BAD THERE IS NO 'FOR SURE' VISUAL CUE FOR THE PLT TO BE ABLE TO TELL THAT THE ACTUAL LATCHES ARE PROPERLY HOOKED. WE PLTS LOOK FOR: A PROPER FIT; SAFETY WIRE; AND HORIZ INSCRIPTED LINES (IF THEY ARE THERE AND AREN'T WORN OFF). WE CAN'T ACTUALLY SEE THE HOOKS INSIDE. NEEDLESS TO SAY; THE MAINT DEPT HAS INSCRIBED 'NEW' LINES FOR US PLTS TO BE ABLE TO ALMOST GUARANTEE COWLING SECURITY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ENG COWLING IS SECURED BY 4 LATCHES; 2 ON EACH SIDE; AND THE R AFT LATCH ON THE L ENG WAS NOT SECURED. THE RPTR SAID THE LATCHES ARE OF A ROTARY TYPE WITH NO EXTERIOR VISUAL INDICATION THAT THE INTERIOR HOOK IS ENGAGED AND LOCKED. THE RPTR SAID AT EACH LATCH LOCATION SAFETY WIRE IS USED TO SECURE THE TOP COWLING TO THE LOWER COWLING BUT IN THE AFT R LATCH LOCATION THE COWLING RAISED ABOUT 1 INCH AND STRETCHED THE WIRE.