Narrative:

Maintenance procedure was to replace #2 engine outboard forward side mount aft isolator which required inboard forward side mount and top forward mount to be loosened. Instead; it was disassembled as well and I did not focus on the inboard mount as much as I focused on the outboard mount. Consequently; I missed the assembly of inboard mount and did not detect the spacer not installed internally between isolators. Miscom between mechanics and me; the inspector. More focus on my part; not allowing myself to be caught up in the rush to get airplanes out and slowing down. Supplemental information from acn 774075: the r-hand forward side mount was removed and replaced to accomplish the above technical callout. In order to replace the r-hand forward side mount; the l-hand forward side mount and the top forward mount were required to be removed. All 3 forward mounts were removed. A new mount was installed in the r-hand forward side mount location; and the forward top and l-hand forward side mounts were reinstalled. Upon reassembly of the l-hand forward side mount; the spacer that fits inside the pads was (inadvertently) not reinstalled. About 1 week later; the aircraft came in again for maintenance for an 'a' check. A mechanic opened the side cowl doors on the #2 engine and found the spacer lying in the lower cowl. Maintenance investigated; and correctly ascertained that the spacer was missing from the l-hand forward side mount; due to the appearance and condition of the mount. Maintenance wrote a non routine card to replace the mount. The mount was replaced. The other mounts were inspected for defects and no other defects were noted. Supplemental information from acn 774755: I was working with mr X to replace aft portion of forward outboard mount on #2 engine. To replace the aft portion; it is required to remove both forward mounts and the top mount. Once the outboard portion was replaced; I reassembled the outboard mount and installed mounting hardware. Mr X did the same for the inboard mount. We then torqued the mounts; I held the bolt heads while mr X torqued the nuts. I installed the cotter pins. Mr Y was the inspector. I did not verify that mr X knew the correct stack-up of the engine mount; he had not asked how it went; so I thought he knew. I had been up approximately 20 hours; it was my first night back on after 2 weeks of being off; vacation and training. Supplemental information from acn 778032: an engine mount spacer was left uninstalled and within the cowling of aircraft X. There were 3 people directly involved with the task. The event took place at the ZZZ maintenance hangar. I was assigned by my lead to assist mr Z with the engine mounts on aircraft X. I remember the task was very stressful because of the difficulty in getting the mounts installed. I was physically and mentally getting exhausted due to the fact that in order to help mr Z to get his mount installed; I had to repeatedly move the engine back and forth from a very uncomfortable position for an extended period of time. I don't recall who took out the original mounts and installed the new ones onto the aircraft and/or who torqued the hardware. My only memory I can give is that I do remember how difficult of a time it was to get the new mounts installed.

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Original NASA ASRS Text

Title: A (BOMBARDIER) DEHAVILLAND DHC-8-200 ACFT MAINT TECHNICAL CALLOUT REQUIRED THE #2 ENG R HAND FORWARD; OUTBOARD ENG MOUNT TO BE REPLACED. FORWARD LEFT MOUNT SPACER NOT REINSTALLED WHEN ALL THREE ENG MOUNTS REASSEMBLED.

Narrative: MAINT PROC WAS TO REPLACE #2 ENG OUTBOARD FORWARD SIDE MOUNT AFT ISOLATOR WHICH REQUIRED INBOARD FORWARD SIDE MOUNT AND TOP FORWARD MOUNT TO BE LOOSENED. INSTEAD; IT WAS DISASSEMBLED AS WELL AND I DID NOT FOCUS ON THE INBOARD MOUNT AS MUCH AS I FOCUSED ON THE OUTBOARD MOUNT. CONSEQUENTLY; I MISSED THE ASSEMBLY OF INBOARD MOUNT AND DID NOT DETECT THE SPACER NOT INSTALLED INTERNALLY BTWN ISOLATORS. MISCOM BTWN MECHS AND ME; THE INSPECTOR. MORE FOCUS ON MY PART; NOT ALLOWING MYSELF TO BE CAUGHT UP IN THE RUSH TO GET AIRPLANES OUT AND SLOWING DOWN. SUPPLEMENTAL INFO FROM ACN 774075: THE R-HAND FORWARD SIDE MOUNT WAS REMOVED AND REPLACED TO ACCOMPLISH THE ABOVE TECHNICAL CALLOUT. IN ORDER TO REPLACE THE R-HAND FORWARD SIDE MOUNT; THE L-HAND FORWARD SIDE MOUNT AND THE TOP FORWARD MOUNT WERE REQUIRED TO BE REMOVED. ALL 3 FORWARD MOUNTS WERE REMOVED. A NEW MOUNT WAS INSTALLED IN THE R-HAND FORWARD SIDE MOUNT LOCATION; AND THE FORWARD TOP AND L-HAND FORWARD SIDE MOUNTS WERE REINSTALLED. UPON REASSEMBLY OF THE L-HAND FORWARD SIDE MOUNT; THE SPACER THAT FITS INSIDE THE PADS WAS (INADVERTENTLY) NOT REINSTALLED. ABOUT 1 WK LATER; THE ACFT CAME IN AGAIN FOR MAINT FOR AN 'A' CHK. A MECH OPENED THE SIDE COWL DOORS ON THE #2 ENG AND FOUND THE SPACER LYING IN THE LOWER COWL. MAINT INVESTIGATED; AND CORRECTLY ASCERTAINED THAT THE SPACER WAS MISSING FROM THE L-HAND FORWARD SIDE MOUNT; DUE TO THE APPEARANCE AND CONDITION OF THE MOUNT. MAINT WROTE A NON ROUTINE CARD TO REPLACE THE MOUNT. THE MOUNT WAS REPLACED. THE OTHER MOUNTS WERE INSPECTED FOR DEFECTS AND NO OTHER DEFECTS WERE NOTED. SUPPLEMENTAL INFO FROM ACN 774755: I WAS WORKING WITH MR X TO REPLACE AFT PORTION OF FORWARD OUTBOARD MOUNT ON #2 ENG. TO REPLACE THE AFT PORTION; IT IS REQUIRED TO REMOVE BOTH FORWARD MOUNTS AND THE TOP MOUNT. ONCE THE OUTBOARD PORTION WAS REPLACED; I REASSEMBLED THE OUTBOARD MOUNT AND INSTALLED MOUNTING HARDWARE. MR X DID THE SAME FOR THE INBOARD MOUNT. WE THEN TORQUED THE MOUNTS; I HELD THE BOLT HEADS WHILE MR X TORQUED THE NUTS. I INSTALLED THE COTTER PINS. MR Y WAS THE INSPECTOR. I DID NOT VERIFY THAT MR X KNEW THE CORRECT STACK-UP OF THE ENG MOUNT; HE HAD NOT ASKED HOW IT WENT; SO I THOUGHT HE KNEW. I HAD BEEN UP APPROX 20 HRS; IT WAS MY FIRST NIGHT BACK ON AFTER 2 WKS OF BEING OFF; VACATION AND TRAINING. SUPPLEMENTAL INFO FROM ACN 778032: AN ENG MOUNT SPACER WAS LEFT UNINSTALLED AND WITHIN THE COWLING OF ACFT X. THERE WERE 3 PEOPLE DIRECTLY INVOLVED WITH THE TASK. THE EVENT TOOK PLACE AT THE ZZZ MAINT HANGAR. I WAS ASSIGNED BY MY LEAD TO ASSIST MR Z WITH THE ENG MOUNTS ON ACFT X. I REMEMBER THE TASK WAS VERY STRESSFUL BECAUSE OF THE DIFFICULTY IN GETTING THE MOUNTS INSTALLED. I WAS PHYSICALLY AND MENTALLY GETTING EXHAUSTED DUE TO THE FACT THAT IN ORDER TO HELP MR Z TO GET HIS MOUNT INSTALLED; I HAD TO REPEATEDLY MOVE THE ENG BACK AND FORTH FROM A VERY UNCOMFORTABLE POS FOR AN EXTENDED PERIOD OF TIME. I DON'T RECALL WHO TOOK OUT THE ORIGINAL MOUNTS AND INSTALLED THE NEW ONES ONTO THE ACFT AND/OR WHO TORQUED THE HARDWARE. MY ONLY MEMORY I CAN GIVE IS THAT I DO REMEMBER HOW DIFFICULT OF A TIME IT WAS TO GET THE NEW MOUNTS INSTALLED.

Data retrieved from NASA's ASRS site as of May 2009 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.