AN ACR MD-80 COULD NOT LIFT ITS LNDG GEAR AFTER TKOF.

Narrative

FLT TOOK OFF FROM NEWARK; MD-80. GEAR HANDLE RETRACTED (RAISED) NORMALLY; BUT GEAR DID NOT RETRACT. TROUBLESHOOTING; THE FO NOTICED THE LATCH/COVER OVER THE 'EMER GEAR EXTENSION LEVER' HAD BEEN AJAR; ALTHOUGH THE LEVER ITSELF APPEARED FULLY CLOSED. WE DECIDED TO TRY PULLING THE HANDLE AND RESETTING IT; THAT IT WAS NOT FULLY CLOSED; THUS BYPASSING OR NEGATING THE GEAR HANDLE. SO I HAD HIM OPEN AND RECLOSE THE EMER GEAR EXTENSION LEVER. THE ONLY CHANGE WAS THAT THE GEAR DOORS NOW OPENED; AND THE 'GEAR DOOR OPEN' LIGHT CAME ON IN THE COCKPIT. THE GEAR HANDLE WAS RAISED; BUT THE GEAR DID NOT RETRACT. I WAS ADVISED BY MAINT THAT THEY BELIEVED THEY KNEW THE PROB; THAT THE 'GEAR DOOR BYPASS' LEVER HAD BEEN LEFT OPEN. THIS BYPASSES HYD PRESSURE TO THE GEAR AND ALLOWS THE DOORS ON THE MAIN GEAR TO BE MANUALLY OPENED ON THE GND. THE FO WAS PRETTY CERTAIN HE'D NOTED IT WAS CLOSED DURING HIS WALKAROUND. WE ADVISED APCH CTL AND THEN TWR THAT WE WOULD BE STOPPING ON THE RWY AFTER LNDG SO THAT MAINT COULD CHK THE PLANE. SINCE THE DOORS WOULD BE OPEN; THEY WOULD CONTACT THE RWY AND WE WOULDN'T TAXI UNTIL MAINT HAD CLOSED THE GEAR DOORS. LANDED WITHOUT PROBS; EMER EQUIP AND OUR MAINT PEOPLE MET THE PLANE UPON STOPPING. MAINT NOTED THE BYPASS OPEN; THE GEAR DOOR BUMPERS (INSTALLED TO ABSORB FORCES OF DOORS RUBBING ALONG THE GND WHEN THE DOOR WILL NOT CLOSE) WELL WORN; AND SOME APPARENT DAMAGE TO THE L GEAR DOOR. MECHS THEN CLOSED THE GEAR BYPASS LEVER; DOORS CLOSED; AND WE TAXIED TO GATE. THE FO HAD NOTED ON HIS WALKAROUND THAT THE L GEAR STRUT SEEMED UNDEREXTENDED; AND HAD REQUESTED THAT A MECH CHK IT OUT. THE MECH HAD OPENED THE BYPASS; BUT NOT OPENED THE DOORS THEMSELVES. HE THEN SVCED THE STRUT; WHICH DOES NOT REQUIRE OPENING THE DOORS; AND FORGOT TO CLOSE THE BYPASS. UPON HEARING THAT OUR GEAR WOULDN'T GO UP; HE TOLD HIS SUPVRS THAT HE'D FORGOTTEN TO CLOSE THE BYPASS. HENCE OUR PROB. SUPPLEMENTAL INFORMATION FROM ACN 262267: MD-80 TYPE. RELEASED BYPASS VALVE HANDLE TO LOWER MLG DOORS TO SEE X-DIMENSION PLACARD IN WHEEL WELL FOR MAIN STRUT SVC. THEN I DIDN'T LOWER DOORS; USED MAINT MANUAL PRINTOUT FOR X-DIMENSION. DIDN'T RESET BYPASS HANDLE. LNDG GEAR WILL NOT RETRACT IN THIS CONDITION. ACFT RETURNED EWR; NO FURTHER PROBS.