AN APCHING; LNDG; MD80 PIC CHANGES THE VHF TO GND CTL FREQ AT 500 FT AGL PRIOR TO LNDG AT ORD; IL.

Narrative

I WAS FLYING THE ILS RWY 9R APCH TO ORD. AT THE OM; THE CAPT (PNF) SWITCHED FROM APCH CTL TO TWR AND RECEIVED LNDG CLRNC FOR RWY 9R. THE CAPT THEN COMPLETED THE REMAINING ITEMS ON THE BEFORE LNDG CHKLIST. AT 500 FT AGL; THE CAPT MADE THE REQUIRED CALLOUT OF SINK RATE AND APCH SPD. HE THEN SWITCHED THE ACTIVE COM FREQ FROM TWR TO GND CTL PRIOR TO LNDG. THE COM RADIO HAS A DUAL HEAD WITH BOTH AN ACTIVE AND INACTIVE SIDE. THE INACTIVE SIDE HAS A RED BAR ACROSS THE FREQ WINDOW. THE CAPT HAD INTENDED TO PLACE THE GND CTL FREQ IN THE INACTIVE SIDE; BUT INSTEAD; SWITCHED THE ACTIVE TWR FREQ TO GND CTL PRIOR TO LNDG. AFTER THE LNDG ROLL; I RELINQUISHED CTL OF THE ACFT TO THE CAPT. IT WAS AT THIS TIME I REALIZED THAT WE WERE NO LONGER ON THE TWR FREQ. AFTER CLRING THE RWY ONTO A TXWY; GND CTL CLRED US TO THE GATE. THERE WERE NO TFC CONFLICTS AND NO COMMENT FROM GND CTL. I BELIEVE THIS WAS A RESULT OF FATIGUE. THE CAPT COMMUTES. HIS HOME IS A 3 HR COMMUTE. RPT TIME FOR THIS TRIP WAS EARLY MORNING. THE CAPT PROBABLY HAD; AT MOST; 4 HRS SLEEP THE NIGHT BEFORE; A 3 HR DRIVE; AND A 12 HR TRIP PRIOR TO THIS EVENT.