LTT PROP HITS GND PWR UNIT IN RAMP OP ACFT PARKING PROC.

Narrative

TAXIED TO GATE AFTER NORMAL LNDG. I FOLLOWED THE MARSHALLER'S INSTRUCTIONS AND STOPPED THE ACFT UPON HIS COMMAND. I SET THE PARKING BRAKE (1 CLICK) THEN REACHED AND LOOKED UP TO THE OVERHEAD PANEL TO COMPLETE THE SHUTDOWN CHKLIST. THE FO'S L HAND WAS OVER THE AVIONICS MASTER SWITCHES TO PREVENT ME FROM TURNING THEM OFF; BECAUSE THE CABIN BRIEFER WAS STILL OPERATING (I WAS NOT AWARE OF THE CABIN BRIEFER STILL RUNNING). I LOOKED AT HIM; WAITING FOR HIM TO TURN OFF THE AVIONICS MASTER. THEN I HEARD THE NOISE OF THE L PROP STRIKING THE GND PWR UNIT. I IMMEDIATELY DROPPED MY HAND TO THE PWR LEVERS; PULLED THEM INTO REVERSE; GRABBED THE PARKING BRAKE; PULLED IT (IT CAME UP 1 CLICK) THEN PRESSED THE ENG STOP BUTTONS. I ALSO PUSHED ON THE TOE BRAKES AS I STARTED THIS REVERSE; BRAKE STOP BUTTON SEQUENCE. THERE WAS NO SENSATION OF MOTION FORWARD OR STOPPING AFTER I INITIALLY SET THE PARKING BRAKE. SUPPLEMENTAL INFO FROM ACN 215914: ONE PROBLEM WAS THE GND PWR UNIT WAS IN THE ACFT SAFE AREA PRIOR TO SHUTDOWN. IN THE FUTURE; PREPOSITIONING OF GND EQUIP IN THE VICINITY OF ACFT SHOULD NOT BE ALLOWED.