Narrative:

I was scheduled to work the night shift. I had completed my assigned work for the night and had just finished my lunch. I was asked by my lead mechanic to assist mechanic 'Y' change the right air cycle machine (acm or air conditioning pack) on an md-80 aircraft that he was assigned to. The acm had to be changed due to an inbound pilot report for insufficient cooling. I was told that mechanic 'Y' had everything disconnected and needed help getting the pack out. When I arrived at the aircraft; the mounting bolts were all that needed to be undone. I noticed a large box on the back of the golf cart mechanic 'Y' was using. The size of this box was consistent with ones that serviceable acms come in; so I thought mechanic 'Y' already had a serviceable acm to replace the one we were removing; which he had. After removing the defective acm; we prepared the serviceable acm to be installed.we got the 'new' acm installed and most of the duct work connected 15 minutes prior to shift change. Two mechanics who work the dayshift were going to finish installing the remaining ducting and perform the leak and operational checks. It was at this time I filled out the FAA-8130 serviceable tag and did not see that the part we installed was a xyz-AAA6 instead of xyz-AAA1; which is required per the ipc (illustrated parts catalog). It was not until the end of the day that I realized that we had installed the incorrect part on the md-80 aircraft. I immediately called company maintenance control and advised them of what had happened. The aircraft was in an airport for the night. Our company does not have aircraft maintenance in this airport. Maintenance control arranged to have a xyz-AAA1 installed before further flight.I signed the field service maintenance report for the changing of the acm before my shift ended. Another mechanic said he would sign for the work he did; and then print my name in the logbook after he completed his work on the aircraft; and he would make sure the airworthiness release was signed. I told him that was fine with me as this is an approved method of documentation.suggest having the different acm's painted different colors; or put a marking of some kind large enough to denote the difference on the acm's. Aircraft configurations [are different because] there are two different internal acm configurations; but they look identical on the outside.

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Original NASA ASRS Text

Title: Two Mechanics report installing an incorrect Air Cycle Machine (ACM) at the right pack position on an MD-80 aircraft. Internal configurations are different; but the two ACMs look identical on outside.

Narrative: I was scheduled to work the night shift. I had completed my assigned work for the night and had just finished my lunch. I was asked by my Lead Mechanic to assist Mechanic 'Y' change the right Air Cycle Machine (ACM or air conditioning pack) on an MD-80 aircraft that he was assigned to. The ACM had to be changed due to an inbound pilot report for insufficient cooling. I was told that Mechanic 'Y' had everything disconnected and needed help getting the pack out. When I arrived at the aircraft; the mounting bolts were all that needed to be undone. I noticed a large box on the back of the golf cart Mechanic 'Y' was using. The size of this box was consistent with ones that serviceable ACMs come in; so I thought Mechanic 'Y' already had a serviceable ACM to replace the one we were removing; which he had. After removing the defective ACM; we prepared the serviceable ACM to be installed.We got the 'new' ACM installed and most of the duct work connected 15 minutes prior to shift change. Two mechanics who work the dayshift were going to finish installing the remaining ducting and perform the Leak and Operational Checks. It was at this time I filled out the FAA-8130 Serviceable Tag and did not see that the part we installed was a XYZ-AAA6 instead of XYZ-AAA1; which is required per the IPC (Illustrated Parts Catalog). It was not until the end of the day that I realized that we had installed the incorrect part on the MD-80 aircraft. I immediately called Company Maintenance Control and advised them of what had happened. The aircraft was in an airport for the night. Our company does not have aircraft maintenance in this airport. Maintenance Control arranged to have a XYZ-AAA1 installed before further flight.I signed the Field Service Maintenance Report for the changing of the ACM before my shift ended. Another Mechanic said he would sign for the work he did; and then print my name in the Logbook after he completed his work on the aircraft; and he would make sure the Airworthiness Release was signed. I told him that was fine with me as this is an approved method of documentation.Suggest having the different ACM's painted different colors; or put a marking of some kind large enough to denote the difference on the ACM's. Aircraft configurations [are different because] there are two different internal ACM configurations; but they look identical on the outside.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.