Date: 201206
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Engine Vibration Indication
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe
Human factors: Workload; Troubleshooting; Time Pressure; Communication Breakdown; Situational Awareness
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Weather; Procedure; Manuals; Logbook Entry; Human Factors; Aircraft; Chart Or Publication
Primary problem: Human Factors

Narrative: Aircraft X; an ERJ-175; came in with write-up of Engine #2 vibrations up to 4.0. The Vibration Accelerometers were changed from Engine #2 by the line mechanics and it was requested that Mechanic Y and I; as Mechanic X; perform the Vibration Engine Run and; just in case it failed; we could simply taxi to the hangar from the Engine Run-Up area. We arrived to the Run-Up area and proceeded with the Engine Vibration Check for Engine #2 in reference to General Electric (GE) CF34-8e Engine Subtask 72-00-00. Mechanic Y was seated in left seat operating aircraft and I was in the right seat monitoring and documenting Engine #2 vibrations and the amount of time [vibrations occurred] at different settings.After some time it was noticed there was an 'ENGINE EXCEEDENCE' message on the EICAS for Engine #1. We shut down Engine #1 and pulled Circuit Breakers to re-set FADEC. Re-started Engine #1 and 'ENG EXCEEDENCE' message was gone. We continued with the Engine Vibration Check for Engine #2 and brought up Engine #1 to match settings to keep in comparison with Engine #2. Engine #2 was found within limits. We never got another 'ENG Exceedence' message so we figured it was good. I signed-off the ENG #2 Vibration Check since it was I who was monitoring the ENG-2 and [vibration] times.The following day I spoke to my Maintenance Manager and was asked about the details of Aircraft X and the 'ENG Exceedence' message on Engine #1. After briefly explaining the circumstances to the Maintenance Manager; he explained to me in reference to the GE Manual [that] if an 'ENG EXCEEDENCE' message is found; a Boroscope [Inspection] is required. We didn't think it would be an issue; since the EICAS message was cleared and didn't return. I realize now; at the very least I should have asked my Supervisor about any questions or concerns that might have arose before returning the aircraft to service. Boroscope was completed and found no damage to Engine #1.Recommend paying better attention to anything and everything that might pop up as an EICAS message and not worry so much about getting the aircraft back in service; to ensure complete 100% compliance; anything not sure about; to double check with immediate supervisors and Maintenance Manuals.


Second narrative: After two Line Maintenance guys Removed and Replaced (R/R) Accelerometers on right-hand engine of Aircraft X; an ERJ-175; for high vibrations [I received] a line call; asking me; as Mechanic Y; and Mechanic X to perform engine runs to check for high vibration on the right-hand engine. I; as the Taxi Mechanic; and Mechanic X right-hand side; went to the Engine Run-Up area to perform Engine Checks for right-hand engine. Checks were good; so we decided to check left-hand engine to get comparison of vibration; just to see; Check was not officially needed; just a comparison. In the process of checking; left-hand engine went to 1009 degrees for three seconds and went back to normal. FADEC did its job. An EICAS message appeared 'Engine #1 EXCEEDENCE'. We checked Central Maintenance Computer (CMC); no faults or Line Replaceable Units (LRU's) at fault. Shut down Engine #1 and reset Circuit Breakers. Then started Engine #1 again and ran it up to max a couple of times and never got Exceedence [message] again. We brought Aircraft X back to gate. Mechanic X signed logbook and handed it over to pilot. The next day; five flights later; a pilot noticed the exceedence message on the CMC Engine Page and reported to Maintenance Control. In doing so; flights were canceled and Aircraft X [was] ferried for Boroscope [Inspections]. Engine #1 turned out to be good; no damage found. [Recommend] reporting to supervisor [and] do more research.


Synopsis: Two Mechanics were informed by their Maintenance Manager that required Boroscope Inspections had not been accomplished after they had performed Engine Vibration Run Checks on both GE CF-34 engines for 'ENGINE EXCEEDENCE' EICAS messages. Aircraft; an ERJ-175; was released aircraft for service. It was later grounded and flights canceled.