B-727 FREIGHTER OPERATED WITH A MISDIAGNOSIS ON THE INOP AFT STAIR LIGHT WARNING SYS.

Narrative

THE WX IN THE NE HAD BEEN BITTERLY COLD -- RECORD LOW TEMPS. THE RAMP WAS COVERED WITH A LAYER OF COMPACTED SNOW AND ICE. THE 'AFT AIRSTAIR' UNLOCKED LIGHT ON OUR B- 727 HAD BEEN DEFERRED BY MAINT. SO; BESIDES THE NORMAL VERIFICATION FROM THE MECH THAT THE STAIRS WERE UP AND LOCKED; WE HAD NO INDICATION THAT THE STAIRS MIGHT BE UNLOCKED; I.E.; THE UNLOCKED LIGHT WAS ILLUMINATED. DURING THE PUSHBACK AT EWR THE MECH SAW THE STAIRS COME UNLOCKED AND FALL DOWN. THE PUSH WAS STOPPED TEMPORARILY. BECAUSE THE RAMP WAS ICY; THE STAIRS SLID EASILY AND NO DAMAGE RESULTED. THE MECH RECLOSED AND LOCKED THE STAIRS UP. THE PUSH CONTINUED AND WE DEPARTED FOR ROC. THE FLT WAS UNEVENTFUL. AFTER LNDG ON RWY 22 WE TAXIED NE ON TXWY B. GND CTL AT ROC ASKED US IF WE KNEW WE WERE DRAGGING OUR AFT STAIRS. OBVIOUSLY; WE DIDN'T KNOW AND IMMEDIATELY STOPPED TAXIING. WE CALLED OUR MAINT IN ROC. THEY CAME OUT; PUT THE STAIRS BACK UP AND FOLLOWED US TO THE GATE TO ENSURE THAT THE STAIRS REMAINED UP. THE MECH SAID HE FOUND ICE ON SOME CTL CABLES; BROKE THEM FREE AND NOW 'ALL WAS WELL.' THE CAPT PRUDENTLY DECIDED THAT ADDITIONAL TROUBLE-SHOOTING WAS INDICATED. WE WENT INTO CREW REST. THAT EVENING WE SHOWED TO FLY ROC TO DTW TO EWR. MAINT HAD FOUND THE STAIR OPERATING MECHANISM WORN. THE STAIRS WERE SECURED UP AND INOP. THE 2 LEGS WERE FLOWN UNEVENTFULLY. ANOTHER FINE' MURPHIAN' EXAMPLE.