Date: 201212
Location: ZZZ.Airport, US
Aircraft: Brasilia EMB-120 All Series
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Engine Oil Seals
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Inspection Authority; Maintenance Airframe
Human factors: Training / Qualification; Physiological - Other; Situational Awareness; Confusion; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Incorrect / Not Installed / Unavailable Part; Human Factors; Aircraft; Company Policy
Primary problem: Company Policy

Narrative: I was being trained on how to install a Carbon Seal on # 1 Engine (E1). I was instructed how to do so and given information on the Service Bulletin; but not [for] removal and installation of the seal; as I was being instructed how to do so; I removed the old seal and O-Ring. I was given a new seal but not a new O-Ring. I installed a new seal and installed the housing back in the engine; but I never installed the O-ring. The aircraft sat in Maintenance for a few more days and upon Run Checks; no leaks were noted. The aircraft made its flight and developed a large oil leak. It made its first few legs and had to divert on a later leg. The training Mechanic was flown up to ZZZ1 airport to repair the leak and another airplane was sent to carry the passengers. The cause of the oil leak was found to be the missing O-ring on the housing. The factors I felt caused this were my lack of training on how to use the Service Manual and stress from Management. I also had a head cold that day but with a lack of sick days; financially it is hard to take time away from work. The Shop Supervisor was putting a lot of pressure on us to get the airplane done and we became rushed and instead of getting all of our proper paperwork the Lead on the airplane just told me how to do the job; instead of getting all of the paperwork. I was just simply instructed how to do the task and the Lead was unable to watch over just me for the task; as he was being pressured to get the rest of the inspection done and was unable to help me the whole time. If proper training and time was allotted to do the task I think that the situation could have been avoided. I also should have taken the time to get all the paperwork for the task; even though I was working with another Mechanic on the task; so in the case where the other person is not there the whole time I [would] still have had the proper steps to complete the task. Another factor is I should have just taken the day off since I was not feeling 100%.

Callback: Reporter stated his company operates under a FAR Part 121 operation. They are not a Contracted Service and work on their own aircraft. The flight delay selected on the form was the delay incurred from the oil loss due to the missing O-ring. The flight cancellation was due to Maintenance realizing they could not get the aircraft repaired due to parts not readily available. Another aircraft did fly the passengers out of ZZZ. Reporter stated his company deducted two hundred dollars from his paycheck for hours he had already worked; as discipline for not installing the O-ring. The Maintenance Shop Supervisor who is fairly new and always pressuring their mechanics; was given a verbal counseling.



Synopsis: While under continuous schedule pressure from their Shop Supervisor; a Mechanic under training; failed to install an O-ring during a Carbon Seal replacement on #1 Engine of an EMB-120 aircraft. The aircraft had to divert after several flights due to engine oil loss.