A B737-700 NEW DELIVERY ACFT; STILL UNDER FAR PART 91 REGS; HAD THE APU FUEL/HYD OVER SERVICE DRAIN MAST ROBBED FOR A FAR PART 121 ACFT.

Narrative

ACFT X ARRIVED AT THE GATE IN ZZZ1 AND HAD HYDRAULIC FLUID LEAKING FROM ABOVE THE PANEL THAT THE APU FUEL/HYDRAULIC OVER SERVICE DRAIN MAST IS MOUNTED TO. IT WAS DETERMINED BY LOCAL MAINT THAT THE ATTACH FITTING ON THE DRAIN MAST FOR THE HYDRAULIC OVER SERVICE LINE WAS DAMAGED. IT COULD NOT BE REPAIRED AND THE DRAIN MAST NEEDED TO BE REPLACED. OUR AIRLINE WAS OUT OF STOCK ON THE DRAIN MAST AS WAS BOEING. WE WERE GOING TO HAVE TO TAKE THE ACFT OUT OF SERVICE FOR THE REMAINDER OF THE DAY BECAUSE WE COULD NOT GET THIS PART. SOMEONE IN ZZZ1 MAINT MADE THE SUGGESTION THAT WE WERE ABOUT TO TAKE DELIVERY OF A BRAND NEW ACFT FROM BOEING; AND WE SHOULD ROB THE PART FROM THAT ACFT. AFTER RESEARCHING THE IPC; ILLUSTRATED PARTS CATALOG; I DETERMINED THAT THE EFFECTIVITY WAS THE SAME FOR BOTH ACFT. THE NEW ACFT WAS GOING TO SPEND A COUPLE OF DAYS IN THE ZZZ1 HANGAR HAVING SOME MAINT WORK PERFORMED ON IT. THIS WOULD THEN GIVE US A COUPLE DAYS TO TRY AND PURCHASE THE DRAIN MAST FROM SOMEONE ELSE. I WAS UNSURE IF WE SHOULD DO THIS. I ASKED SOME OF MY FELLOW MAINT CTLRS AND MY SUPERVISOR IF WE COULD DO THIS. WE ALL CAME TO THE CONCLUSION THAT THIS WAS NOW OUR COMPANY'S AIRCRAFT; AND IT WOULD BE FINE. I THOUGHT THAT WHEN WE TOOK DELIVERY OF THE ACFT THAT IS WHEN IT BECAME OURS. I THEN TOLD THE ZZZ1 MAINT SUPERVISOR TO GO AHEAD AND ROB THE DRAIN MAST FROM THE NEW ACFT WHEN IT ARRIVED. WHEN THE ACFT ARRIVED IN ZZZ1; IT WENT TO THE HANGAR AND THE DRAIN MAST WAS REMOVED AND ROBBED. THE MAST WAS SENT BACK OVER TO THE LINE AND INSTALLED ON ACFT X. THE ACFT WAS OUT OF SERVICE FROM XA:45-XD:15. A COUPLE OF HOURS LATER MY MANAGER CALLED AND SAID WE HAD INSTALLED AN ILLEGAL PART ON ACFT X. SOMEONE IN ZZZ HAD CONTACTED HIM AND TOLD HIM WHAT HAPPENED. HE SAID THAT THE NEW ACFT WAS STILL UNDER FAR 91 AND NOT UNDER FAR 121. WE COULD NOT INTERMIX THE PARTS UNTIL THIS ACFT COMES UNDER FAR 121. WHEN WE WERE TOLD THIS; ACFT X HAD ALREADY FLOWN ONE FLT AND WAS IN THE MIDDLE OF ITS SECOND FLT. IT WAS ON ITS WAY TO ZZZ2. WHEN ACFT X ARRIVED IN ZZZ2 WE TOOK IT OUT OF SERVICE. I WAS TOLD WE WERE GOING TO ROB THE PART FROM ANOTHER ACFT THAT WAS IN FOR A HEAVY MAINT VISIT. THIS HAPPENED AT THE END OF MY SHIFT AND I DO NOT KNOW WHAT TRANSPIRED AFTER AIRCRAFT X ARRIVED IN ZZZ2. AT NO TIME WAS PAX SAFETY COMPROMISED. I TRIED TO DO WHAT I THOUGHT WAS BEST FOR MY AIRLINE AND WHAT WAS BEST FOR OUR PAX.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE APU FUEL/HYD OVER SERVICE DRAIN MAST WAS JUST AFT OF THE LH/RH MAIN WHEEL WELL CUTOUTS.