EC135
Maintenance Inspection Authority
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Human Factors; Manuals
[A maintenance technician] and I began packing an engine for shipment and found the pin to the aft mount would not fit. We discovered bushings that needed to be removed in order for the pin to fit and; I instantly wondered if the new engine we just installed had the bushings installed in the aft mount. We originally removed the #1 engine to facilitate Maintenance. The original plan was for a Pratt and Whitney Team to swap a combustion liner in the field and this engine would be reinstalled. After removal I performed an inspection of the engine mounts and all mounts; fittings; and bushings checked out ok. The Pratt and Whitney team arrived and during their combustion liner swap discovered more damage and the engine would need to go to the manufacturer for repairs.The decision was made to replace the engine. The engine arrived; [the maintenance technician] and I began installation [and] engine installation went well we continued installation and completed installation on IAW EC135 MM. During check flights we discovered Maintenance Manuals on company Web site was not current. We notified [the company] and was informed that current revision will be installed. We completed Check flights and signed off the aircraft return to service. The aircraft logged around 2 hours since engine replacement. The aircraft arrived this afternoon and [another maintenance technician] and I checked the aft mount to discover bushings not installed. We took the aircraft out of service and made repairs. We inspected all handwork and did not find any discrepancies. We conducted all maintenance according to Maintenance Manual (MM) and I am still disappointed in myself for missing those bushings. I believe the error came from us installing what we believed to be a complete and serviceable engine. Minor build up was required and manuals where used during all maintenance. Because a late decision was made to install a new engine I did not think to inspect new engine mounts after all mounts had already been inspected. The bushings are tiny and hidden in the aft engine mount and easy to miss I did not think to check aft mount until we had to remove them for engine packing. We did work late hours during this whole event but nothing unreasonable at no time did I feel too tired or unsafe. [The maintenance technician] and I reviewed the RII and did not see mounts. One remedy to this problem I would like to recommend is to add a caution or note in the RII that includes special attention to the aft engine mounts for bushings.
The original plan was to remove #1 Engine from airframe to have [manufacturer] perform on-site replacement of Combustion Liner. Upon vendor completion; same engine was to be re-installed on the airframe. EC-135 Inspection of Engine Mounts was performed at this time. During vendor inspection; it was determined additional internal depot-level repairs were recommended; and another engine was ordered. Engine was originally scheduled for delivery by XA30 Local Time. Plan was to install engine with our Lead Mechanic as [another technician] was out of town on company business. The engine did not show up as scheduled; and was delivered 24 hours later. Due to this fact; a decision was made for the mechanics to come in to install the engine. I was not feeling great; and had requested to perform Maintenance on [another day]. The decision was made to continue with engine installation [on a later day].[Another technician] & I arrived and began engine build-up; following the manuals printed that morning. The new engine was mostly complete; however some small components such as the Air Box Enclosure; Water Injection Fitting; HMU Manual Control Linkage etc. - still needed to be swapped over from the previous engine; still on the Engine Stand provided by the P&W Vendor. We had the engine physically installed by that evening; however we both began to feel we needed to stop for the evening as it had been a long day; we had made good progress; and we were reaching the 12-hour mark. Additionally; the hangar lighting is not very bright and there are no provisions for additional lighting as the entire hangar only has a single point; 4-Outlet Electrical Outlet. We decided to make notes of where we left off; clean up; account for tools; and re-inspect everything on [following workday] Morning; which we did.[Later]; we looked over the installation; and verified all bolts and lines were torqued and safetied. We continued on with Driveshaft Installation; took another good look together; and proceeded to install firewalls; ejector; cowlings; etc. We opted to wait to complete Leak Checks; and Operational Flight Checks due to inclement weather outside to ensure a proper leak check. We [then] performed leak checks and installed cowlings in preparation for ops flight checks. We flew for approximately an hour following the procedures printed that and supposed to be up to date; and encountered an issue with our high altitude N2 adjustment. We returned to base and contacted a tech rep who informed us our manuals were out of revision. We accessed and printed the current manuals.An email was sent to to inform her of the disparity; and that it created a delay in the return to service. This would normally only be an inconvenience however; we needed to complete the maintenance to free up the spare aircraft for use at another base as they were awaiting parts that were scheduled for delivery for an inspection that expired a [following date]. We resumed flight checks with the current manuals and the flight checks were completed without issue. At no time during the flight did we notice any abnormal operating conditions such as vibration or noises resulting from installation. The aircraft was subsequently returned to service.[On another date] I arrived as the aircraft was departing for EMS support while their base aircraft was undergoing maintenance. [Another technician] arrived shortly after. [The other technician] & I began working on removal of old engine from the Engine Stand and attachment to shipping crate in preparation for return to manufacturer for repairs. During installation of the mounts on to the engine; I discovered the Clevis Pin did not fit through the Aft Engine Support Boss. After looking at it for a moment; we revealed the cause to be due to bushings installed in the boss. We removed the bushings and inspected them; and began to wonder if the new engines came with bushings or if they perhaps had been forgotten. The aircraft arrived back shortly thereafter.Upon landing; [another technician] & I greeted the aircraft and spoke to the pilot; He reported no anomalies with the aircraft. We inspected the R/H Engine & compared to the L/H Engine; upon which no determination could be made. After retrieving a 1 Inch Inspection Mirror; we found the L/H Engine (Newly Installed) to be missing the Bushings from the Aft Mount (Z-Strut). We immediately documented the discrepancy in the Aircraft Logbook; informed the pilot; and notified [the] Lead & Regional Maintenance Manager the Aircraft was out of service due to our findings. We printed current manuals; gained access to the #1 Engine 'Z-Strut'; and supported the Engine with a hoist. Once completed; we each verified no tools; rags; or foreign debris were present; all lines and fittings were torque and safetied; and requested the pilot to be a third set of eyes as well. Upon signoff of maintenance performed and verification all tools were accounted for; an Operational Check.Flight was accomplished to verify satisfactory Installation and the aircraft was returned to service.After the aircraft was returned to service; [another technician] & I reviewed the RII Checklist again to see how this could have been missed. We agreed it needs revising. The closest the RII Checklist comes to the mounts. It states 'Thoroughly inspect all maintenance areas for proper installation of Safety Wire; Cotter Pins and Lock Tabs. In limited sight areas use a flashlight and mirror if necessary.'
Two maintenance technicians reported that after installing an engine in a Eurocopter it was discovered they failed to install the bushings in the aft mount.