Bombardier Learjet Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 120; Flight Crew Total 12000
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Company Policy; Human Factors; Aircraft
Observed a 15% split between engines at flight idle during descent. Same problem as reported by previous pilot to [Director of Maintenance]. I was advised by Chief Pilot of this pilot's report and informed me he had a discussion with [Director of Maintenance] and would correct [the] problem prior to dispatch. Upon returning from mission; I noted the problem still existed and the [Director of Maintenance] advised discovering a piece of the fin that connects the N1 (Low Pressure Compressor) fan blades on the #2 engine had broken off and impacted the intake wall and nicked some blades in the secondary fan before being ejected ostensibly through the bypass. This was determined to be the cause of slight vibrations and unusual tone in engine during power changes.I was then advised by the [Director of Maintenance] and Chief Pilot they believed the damage occurred during a flight preceding mine and were closely monitoring the N1 fans on both engines because of strange tones and vibrations reported by several pilots who flew the plane.My question is why the damage wasn't discovered by the mechanics inspection preflight and post flight inspection before being released; especially since the mechanic was performing adjustments due to the recently reported discrepancy. (Damage to N1 was not clearly obvious to a pilot peering in the intake; it required one to look behind the blades.)
Learjet flight crew observed engine anomalies during descent.