Incident Details
On 25 November 2014, during a 96-monthly maintenance check (task 73-30-00-001) on an Embraer 175 aircraft, LOT Aircraft Maintenance Services (LOTAMS) performed a borescope inspection (BSI) on the left engine (ESN 193442). The inspection revealed damage to the 5th stage high-pressure compressor (HPC), including a damaged blade, shroud, and vane mounting seats. Two blades were found to have damage beyond acceptable limits. The engine was replaced with an engine of ESN 193146.
This was the fourth occurrence of engine damage attributed to rotor-stator contact. The modification to address the issue was being introduced during overhaul visits. The discovery was reported to GE, the engine manufacturer. No injuries or fatalities were reported. The aircraft was registered SP-LIE and operated by PLL LOT S.A.
Findings
Inspection results indicated contact between rotor blades and stator blades of the high-pressure compressor. The contact led to damage on multiple components.
Cause
The cause of the incident was contact between rotor blades and stator blades of the high-pressure compressor, occurring due to material fatigue of a stator element.
Preventive Actions
Following the incident, the operator initiated several preventive measures:
- A recommendation was issued for PLL LOT S.A. pilots to use CLIMB2 power instead of CLIMB1.
- A special safety bulletin was issued for Embraer fleet crews regarding a previous engine failure on SP-LIO.
- Engine swaps within the Embraer fleet ensured that each aircraft had at least one engine with the rotor-stator contact modification.
- The engine manufacturer was informed.
- Data transmission from ACARS servers to GE servers was enabled for Embraer 170/175 aircraft with LOAD 25.4 software.
- The damaged engine was replaced.
- Software updates to LOAD 25.4 were scheduled to activate automatic engine data transmission via ACARS to GE.
- Fleet-wide verification of LOAD 25.4 installation and data transmission activation was conducted, with 3-month rechecks for non-compliant aircraft.
- All PLL LOT S.A. engines were scheduled to be modified by 1 April 2015.
- A Continuing Airworthiness Safety Action Group meeting addressed rotor-stator contact.
- A safety bulletin (No. 1/2015) for Embraer fleet flight crew provided information on engine damage cases and planned engine replacements.
- Four engines with the highest time since new were swapped for engines with lower risk.
- A follow-up bulletin was issued after those swaps.
- Updates to LOAD 25.4 were recommended for aircraft SP-LIO and all Embraer 170-100 aircraft.
- Specific engines were listed for modification: ESN 193269, 193412, 193400, 193447, 193444, 193110, and 193146.
- A final bulletin was to be issued after all fleet engines were modified.