A DE HAVILLAND DHC-8-400 ACFT THALES AVIONICS SUITE POST V811 SOFTWARE; MULTI-FUNCTIONAL DISPLAY (MFD) WAS REPLACED WITH A NON-INTERCHANGEABLE PRE V811 SOFTWARE. ACFT GROUNDED.

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REPLACED POST V811 THALES AVIONICS SUITE SOFTWARE WITH NON-INTERCHANGEABILITY PRE-V811 THALES AVIONICS SUITE SOFTWARE. WHEN I CAME IN TO WORK; MY LEAD TOLD ME I NEEDED TO GO TO ZZZ AND MEET ACFT X AND WRITE UP THE #2 MFD REQUIRED REPLACEMENT PER MAINT CTL. I WAS TOLD THAT MAINT CTL ALSO HAD ALREADY ORDERED THE MFD AND HAD STORES SENT IT TO ZZZ. WHEN I GOT TO ZZZ; THE GND SVC AGENT BROUGHT ME THE MFD AND I WAITED TILL ACFT X GOT THERE. WHEN ACFT X LANDED; I GOT IN THE ACFT AND WROTE UP THE #2 MFD AND REMOVED THE MFD. I LOOKED AT THE PART NUMBER OF THE REMOVED UNIT AND SAW PART #XXXX AND THE NEW PART NUMBER SVCABLE TAG PART NUMBER WAS XXXXYY. I DIDN'T REALIZE THAT THE SOFTWARE VERSION NUMBER WAS ON THE BACK OF THE UNIT AT A DIFFERENT LOCATION; SO INSTALLED IT AND IT OPS TESTED GOOD. WHEN I GOT BACK TO BASE; I TRIED TO TAKE IT OFF TAIL AND PLACE THE NEW ONE ON TAIL IN THE MAINT COMPUTER AND IT WOULDN'T LET ME. MY SHIFT WAS OVER AND I ASKED THE NEXT SHIFT TO LOOK INTO IT. THE NEXT MORNING WHEN I CAME IN; I SAW THE PART WAS STILL IN THE SHOP WITH A NOTE ON IT FROM PREVIOUS SHIFT SAYING I NEEDED TO GO TO ENGINEERING AND HAVE THAT PART NUMBER ADDED TO THE MAINT COMPUTER. BECAUSE I WAS SO BUSY THAT DAY; I DIDN'T HAVE A CHANCE TO LOOK INTO IT UNTIL THE END OF THE SHIFT. I LEFT A LITTLE EARLY AND I REMEMBERED THE PART HADN'T BEEN DEALT WITH; SO I CALLED THE LEAD AND ASKED HIM TO LOOK INTO IT. HE CALLED ME ABOUT 1/2 HR LATER AND TOLD ME THE PART WASN'T COMPATIBLE AND TOLD MAINT CTL AND THEY AOG'ED THE ACFT UNTIL THE RIGHT PART WAS INSTALLED. SUPPLEMENTAL INFO FROM ACN 741963: MY UNDERSTANDING IS THAT OUR 'INFO ONLY' QUICK LIST IS NOT TO BE USED FOR INSTALLATION AND THAT THE MAINT COMPUTER WILL NOT LET THE EXPEDITER ISSUE A PART FOR A PARTICULAR ACFT IF THIS PART IS NOT A VALID PART NUMBER. WORKLOAD; CONSTANT DISTR AND NO PARTS ORDERING PERSON IN MAINT CTL CONTRIBUTED TO THE EVENT. SUPPLEMENTAL INFO FROM ACN 741965: WHEN THE TECHNICIAN RETURNED TO THE AVIONICS SHOP; HE TRIED TO REMOVE AND INSTALL THE #2 MFD IN THE MAINT COMPUTER SYS AND IT WOULD NOT LET HIM DO SO. IT WAS AT THIS TIME HE REALIZED THAT THE PART NUMBERS WERE DIFFERENT AND THERE WAS 2 ADDITIONAL NUMBERS AT THE END OF THE BASE NUMBER THAT HE DID NOT NOTICE ON THE UNITS..