During revenue operations of the Embraer 145 fleet, a peculiar behavior of the high pressure section of the AE3007A turbofan was reported by the operators to EMBRAER and Rolls-Royce attention. The engine core speed (high pressure gas generator speed - N2) was higher in the right engine when compared to the left engine, in a random pattern on the fleet, during the take-off phase.
It is common to have different stabilized N2, due the engine control of thrust (N1) and engine conditions. But these differences are usually small and fairly constant on the same aircraft during its entire flight envelope. The reports Embraer and Rolls-Royce were receiving from the field described some significant differences, randomly distributed and that only appeared in specific flight phases.
Engine installations are certified according to very strict regulations. The engine and the airframe manufacturer cover all envisioned scenarios to assess that the engine would be fully operational under any circumstance within the aircraft flight envelope. Yet, sometimes the aircraft operational life can provide us with more lessons to be learned regarding this complex subject that is engine/aircraft interactions.
This paper firstly describes the analysis of field data that led to a working theory on the cause of the aforementioned phenomena.
Finally the paper describes the combined Rolls-Royce and EMBRAER engineering effort was put forward to confirm the hypothesis rose by the field data analysis and understand root cause of the phenomena, through intensive usage of CFD analysis and aircraft testing.