RWY INCURSION BY AN AIR AMBULANCE CESSNA 421 TWIN AT ZZZ.

Narrative

THE SINGLE PLT OP WAS AN IFR AIR AMBULANCE FLT. CLRNC WAS OBTAINED FROM ZZZ TWR CLRNC DELIVERY POS INCLUDING DEP PROC AND ALT OF 5000 FT. UPON CONTACTING GND CTL; WE WERE CLRED TO TAXI FROM THE FBO TO RWY INTXN DEP FROM INTXN E. AS WE COMMENCED TAXI; EXITING THE FBO RAMP AT INTXN K; GND CTL ISSUED A REVISED CLRNC INCLUDING A DIFFERENT DEP AND DIFFERENT INITIAL ALT (3000 FT). DURING THE BRIEF 'HEADS DOWN' PERIOD; WHILE I WAS LOCATING THE NEW DEP CHART AND INPUTTING THE CHANGE INTO THE GPS; I INADVERTENTLY CROSSED THE TXWY; ENTERED RWY; AND BEGAN TAXIING ALONG IT UNDER THE IMPRESSION THAT IT WAS THE TXWY; THE NORMAL RTE TO INTXN E. AS SOON AS I WAS QUERIED BY GND CTL; I REALIZED THE SIT AND IMMEDIATELY EXITED THE RWY VIA THE ADJACENT TXWY. TOTAL TIME ON THE RWY WAS UNDER 30 SECONDS AND THERE WAS NO ACTUAL TFC CONFLICT. THE CAUSE OF THIS INCURSION WAS DISTR FROM THE CORRECT TAXI RTE DUE TO THE LAST-MIN CHANGE IN CLRNC; COMPOUNDED BY THE FACT THAT IT WAS A SINGLE-PLT OP. WE HAVE IMMEDIATELY INSTITUTED A CHANGE IN OPERATING PROCS TO MANDATE THAT AT NO TIME WILL CLRNCS OR AMENDMENTS BE COPIED WHEN OPERATING AS A SINGLE PLT WHILE THE AIRPLANE IS MOVING ON THE GND. INPUTS TO THE GPS SYS WILL SIMILARLY BE CARRIED OUT ONLY WHEN THE AIRPLANE IS AT A STOP. IF NECESSARY; THE AIRPLANE WILL BE STOPPED TO ALLOW THESE ACTIONS. ALTERNATIVELY; CLRNC DELIVERY OR GND CTL POS WILL BE ADVISED THAT WE CANNOT COPY CLRNCS UNTIL WE HAVE REACHED A POS AT WHICH WE CAN STOP THE AIRPLANE WITHOUT IMPEDING OTHER GND TFC; AND WE WILL REQUEST THAT THE NEW CLRNC NOT BE ISSUED UNTIL WE HAVE STOPPED AND ADVISED READY TO COPY IT.