A CRJ700 WAS PUSHED BACK FROM THE GATE WITH THE NOSEWHEEL STEERING ARMED. THE TOW BAR SHEAR PINS BROKE.

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DURING PUSHBACK; I NOTICED THE TUG OPERATOR WATCHING THE TOW BAR CLOSELY; AFTER JUST STARTING THE PUSH. WHEN WE HAD MOVED ABOUT 10-15 FT; HE STOPPED THE PUSH. I ASKED WHAT THE PROB WAS WHILE SIMULTANEOUSLY REALIZING THAT THE NOSEWHEEL STEERING WAS ARMED. I ASKED THE TUG OPERATOR WHAT HAD HAPPENED AND HE SAID THAT 1 OF THE 2 SHEAR PINS ON THE TOW BAR HAD BROKEN. I TOLD HIM THAT THE NOSE STEERING WAS ARMED AND TOLD HIM TO HAVE ALL PERSONNEL STAND CLR TO MAKE SURE THERE WAS NO ONE IN HARM'S WAY; THEN DEACTIVATED THE STEERING. WE HAD BEEN PUSHED MOSTLY STRAIGHT BACK; BUT I DIDN'T WANT TO TAKE THE CHANCE THAT THERE MIGHT BE ANY UNCOMMANDED STEERING OR DEFLECTION WHEN DEACTIVATED. ONCE THE BRAKES HAD BEEN SET; I EXITED THE ACFT AND ASSESSED THE TOW BAR AND ACFT. THERE WAS NO VISIBLE DAMAGE TO THE TOW BAR; EXCEPT THE BROKEN SHEAR PIN; AND OBVIOUSLY NO DAMAGE TO THE ACFT. I TOLD THE GND PERSONNEL THAT I HAD ACCIDENTALLY LEFT THE STEERING ARMED; AND THAT I WAS SORRY I HAD CAUSED THE PROB. A NEW TOW BAR WAS ATTACHED AND WE PUSHED BACK AND CONTINUED WITH OUR FLT. SOMEHOW I HAD OVERLOOKED THE NOSEWHEEL STEERING DURING THE CHKLISTS. I AM VERY PRIDEFUL OF MY PROFESSIONAL APCH TO SAFE ACFT OPS; AND ESPECIALLY CHKLIST USAGE. I DON'T TAKE IT LIGHTLY; THAT I MISSED A CHKLIST ITEM; (ONE WHICH CAN BE VERY HAZARDOUS). I AM VERY AWARE OF THE POSSIBLE DANGERS ASSOCIATED WITH HYDRAULICALLY ACTUATED COMPONENTS. DAMAGE TO THE TOW BAR APPEARED VERY MINOR. AFTER RERUNNING THE SCENARIO IN MY MIND AND CONTEMPLATING WHAT DISTR ME FROM DEACTIVATING THE STEERING; I CALLED THE DUTY OFFICER AND RELATED THE EVENT. AFTER FURTHER THOUGHT ON THE SUBJECT; I BELIEVE NEW FLT DECK FLOWS DUE TO FUEL CONSERVATION; MAY HAVE DISRUPTED MY NORMAL FLOWS. THINGS SUCH AS SHUTTING DOWN 1 ENG FIRST; THROWS IN DIFFERENT IN CHOCKS SHUTDOWN PROCS; AS WELL AS USING DIFFERENT SHUTDOWN PROCS WHEN USING GATE PWR AS OPPOSED TO APU PWR: DIFFERENT SHUTDOWN FLOWS FOR DIFFERING SITUATIONS MAY HAVE ADDED TO MISSING THE NOSEWHEEL STEERING. I HAVE LEARNED FROM THIS; AND WILL REDOUBLE MY EFFORTS TO ASSURE CHKLISTS ARE NEVER DONE DURING TIMES OF DISTR; OR ARE REDONE IN AN ATMOSPHERE CONDUCIVE TO EFFECTIVE CHKLIST COMPLETION IF INTERRUPTED.