A B737 CAPT IS CONCERNED WITH THE INCONSISTENCY OF THE MODE CTL PANEL KNOBS BTWN DIFFERENT SERIES OF B737 ACFT.

Narrative

THIS WAS MY FIRST FLT IN AN ACFT CONFIGURED WITH THE NEW COLLINS MCP. IT IS SOMEWHAT DIFFERENT FROM THE OTHER MCP'S WE HAVE ON THE 300; 500; AND 700. MOST OF THE FEATURES ARE COSMETIC IE; LED TYPE BUTTONS; ETC. ONE OF THE MOST DISCONCERTING ASPECTS; HOWEVER; IS THE SHAPE OF THE SELECTOR KNOBS. ON THE OLDER MCP'S THE HEADING BUTTON AND THE ALT SET BUTTONS HAVE DIFFERENT SHAPES. IN THE COLLINS MCP THE ALT AND HEADING BUTTONS HAVE THE EXACT SAME KNURLING. THE AIRSPEED KNOB ON THE COLLINS IS DEEPLY KNURLED. I THINK IT WOULD BE VERY EASY TO REACH UP TO SET A HEADING AND INADVERTENTLY SET A NEW ALT. THE BUTTONS FEEL THE SAME. (UNLIKE IN THE 300). IF YOU ARE GOING TO HAVE A KNOB WITH DEEP KNURLING; PERHAPS THE ALT KNOB SHOULD BE DEEPLY KNURLED TO IDENTIFY IT AS DIFFERENT. I DON'T KNOW IF WE (COMPANY) CAN CHANGE THIS OR IF THIS IS A CERTIFICATION ISSUE; BUT I THINK IT IS POTENTIALLY DANGEROUS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: UPON CALL BACK; DISCOVERED THAT THE LOCATION OF THE HEADING; ALT; AND AIRSPEED SELECTION KNOBS ARE IN THE SAME LOCATION ON ALL THE DIFFERENT SERIES OF B737. THE ONLY DIFFERENCE IS THAT ON THE NEW B737-700; THE KNOBS ARE THE SAME SIZE AND SHAPE. ON THE B737-300 AND B737-500; THE KNOBS ARE DIFFERENT SHAPES AND SIZES FOR THE ALT; AIRSPEED; AND HEADING. THE RPTR WAS CONCERNED THAT WITH THE KNOBS BEING THE SAME; THAT IT INCREASED THE POSSIBILITY OF A PLT SELECTING THE WRONG KNOB. HOWEVER; THE RPTR ADMITS THAT IF THE SELECTION IS PROPERLY VERIFIED BY BOTH PLTS; THAT THERE SHOULD BE NO PROB. THE RPTR WAS MAINLY QUESTIONING THE REASON THAT BOEING DECIDED TO CHANGE THE SHAPE AND SIZE OF THE KNOB.