Date: 201201
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Weather elements / visibility: cold
Light: Night
Aircraft: Jet/Long Ranger/206
Operator: Air Taxi
Operating under: Part 135
Mission: Ambulance
Flight phase: Parked
Aircraft component: Gearbox
Reporter organization: Air Taxi
Reporter function: Technician
Reporter qualification: Maintenance Airframe
Human factors: Workload; Situational Awareness; Communication Breakdown; Confusion
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Routine Inspection
Result: General Maintenance Action
Contributing factors: Weather; Human Factors; Aircraft; Company Policy; Incorrect / Not Installed / Unavailable Part
Primary problem: Human Factors

Narrative: During an engine replacement the freewheeling unit's aft cap was installed without the proper spacer. I believe this was missed due to weather conditions; the remote location; and being at night (worked with flashlights and plug-in lamps). The question of if the spacer was installed or not was even asked; with the Mechanic installing the aft cap stating 'yes; it's there'. However I was working on another part of the engine and was not involved with the assembly of the freewheeling unit. I do know from now on; any time there is a question; everyone working on the task at hand will stop and double check each other.


Second narrative: During an engine change on a Bell 206L-3 helicopter; Aircraft X; while installing the freewheeling unit; a spacer was not installed. The purpose of the spacer is to hold the split cones and provide proper seal placement on the adapter and aft cap. The problem occurred when myself and another Mechanic were installing the freewheeling unit. The [Electronic] Manual was up and I was reading it step by step and when I asked it the split cones and spacer were installed the other Mechanic confirmed the split cones but was looking at what he called the spacer; which was actually the sleeve over the adapter. I did not confirm the cones and spacer; I did not ensure that we were both looking at the same item and did not communicate the part location; only the name. The temperature was around 35 degrees Fahrenheit. We were not located in a hangar and were using shop lights and head lamps to illuminate the area. With only a wireless card as a source of accessing the Internet; it was very slow to load Maintenance Manuals. I feel that these were not necessarily the causes but are factors worth mentioning that were present during the engine change. I tried to mitigate these risks by limiting time a Mechanic spent in the elements; printing references off in advance; and using every possible light available to us. The problem was discovered when we performed a Visual Inspection (V/I) after questioning if the spacer was installed. I was performing another engine change on Aircraft Y and while installing the freewheeling unit and placing the spacer over the split cones; I began to question whether or not the spacer was installed [on] Aircraft X during that engine change. I immediately contacted the Mechanic that installed the aft cap and asked if he remembered installing the spacer. After discussing it with him; neither of us were sure that we had ever seen the spacer that night. I then called the third Mechanic that had been working with us on the engine change to confirm if he had seen the spacer. He could not recall ever seeing it either. At this point I called the base to determine if the adapter was riding farther in than normal. The Pilot stated that the adapter and aft cap looked correct. There was an 1/8' inch showing on the aft side of the seal; the adapter had no play; and there were no leaks of any sort on the aft cap. After a few minutes I determined that the aircraft should be removed from service until verification of the spacer was confirmed or denied. The aircraft was removed from service; and the Base Mechanic pulled the aft cap and confirmed that the spacer was not installed. At this time I contacted the helicopter's Technical Representative and explained the situation. His recommendation was to inspect all components; and if no damage was found; to order and install the spacer and return the aircraft to service. The correct part number was located and the spacer was ordered and at this time is in transit to the aircraft. The aircraft will not be returned to service until the spacer is installed and an Operational Check is completed. At that point all corrective actions will be completed. In looking back at this situation; I believe that the factors causing the problem were a lack of training and miscommunication which led to the spacer not being installed. The Bell 206L+ aircraft are new to some of our bases that have been operating only 'L' model aircraft. There are quite a few things different and training needs to be conducted for mechanics moving into an 'L+' airframe. Using the appropriate nomenclature for components would have eliminated the error of two mechanics referring to one component by two different names. All appropriate references were used and procedures followed. The spacer is not used on a [base model] 206 part number freewheeling unit. So; better training would allow each Mechanic to have a working knowledge of the systems and components on their airframe that they may not be able to seeor touch everyday. Using standard terminology and confirming that all mechanics working together are calling the component the same name can reduce confusion. I think that the issue was not due to poor judgment or decisions; but due to lack of training and knowledge of the systems being worked. This allowed the spacer to be overlooked and not installed.


Synopsis: Three mechanics report a required spacer was not installed at the aft cap position on the aft side of a Bell 206L-3 helicopter's engine gearbox case during an engine change; outside; at night; in cold temperatures with limited lighting and communication terminology issues.