A DC10-30 ON INITIAL CLB AT 500 FT DECLARED AN EMER AND DIVERTED DUE TO CTR LNDG GEAR UNSAFE INDICATION. CAUSED BY A FAILED RETRACT CYLINDER.

Narrative

ON TKOF FROM ZZZ; RAISED THE GEAR; FO NOTICED A RED LIGHT IN THE CTR GEAR. WE CONFIRMED THE UNSAFE GEAR INDICATION WITH OUR SECONDARY INSTS. IMMEDIATELY ADVISED APCH CTL THAT WE HAD A CTR GEAR UNSAFE INDICATION; REQUESTED A LEVELOFF AT 5000 FT; AND KEPT OUR SPD DOWN TO 210 KTS. WE REQUESTED VECTORS BACK TO RWY 36C AT ZZZ. IN ACCORDANCE WITH OUR CHKLIST; WE PUT THE GEAR HANDLE DOWN AND STILL CONTINUED TO HAVE AN UNSAFE GEAR INDICATION. DECLARED AN EMER; REQUESTED PERMISSION TO DUMP FUEL. ASKED APCH TO VECTOR US AROUND S OF THE FIELD WHILE WE ACCOMPLISHED NUMEROUS ABNORMAL CHKLISTS CONCERNING OUR UNSAFE GEAR. COORDINATED WITH APCH TO RELAY TO TWR THAT WE WOULD BE STOPPING STRAIGHT AHEAD ON THE RWY AND 'MAINT' PIN OUR GEARS AND TOW US BACK INTO THE GATE. ON SHORT FINAL; HAD TWR LOOK US OVER AND CONFIRM CTR GEAR WAS UP. AN UNEVENTFUL LNDG ACCOMPLISHED. MAINT LATER CONFIRMED A HYD CTR STRUT LEAK CAUSED THE CTR GEAR TO BE STUCK IN A PARTIALLY DOWN POS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AFTER LNDG; MAINT DISCOVERED THE END CAP ON THE CTR MAIN GEAR RETRACT CYLINDER HAD FAILED WITH THE LNDG GEAR PARTIALLY RETRACTED TO ABOUT 45 DEGS.