EMB ERJ 170/175 ER/LR
Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Aircraft; Equipment / Tooling; Human Factors
We were to fly this aircraft on a revenue flight. The previous Captain reported a DMI [Deferred Maintenance Instruction] on the aircraft for high LP vibrations. The procedure via Maintenance was to follow the QRH and keep the LP out of the amber range. He was flight planned at FL350. Following the procedure he was unable to climb above FL290. This was a N1 of 78%. I asked Dispatch if we had any degraded performance for the aircraft with this DMI. He responded no. I asked Maintenance if there was any special performance to confirm Dispatch. They also reported no. I departed and was flight planned at FL350. We were only able to reach FL270 and an N1 of 75% following the QRH. I was very uncomfortable flying the aircraft with an engine that had unknown performance. What was my single engine performance if the good engine failed? What was my drift down? What is my performance period? I asked everyone I could. The best answer that I got was it was an FAA approved DMI and the aircraft could be flown for 50 hours. There where no added restrictions. The aircraft should be lubed properly to not have high LP vibs. The aircraft should not be flown with an unknown level of degraded engine performance. We are flying to airports with high MEA's out west. How do you fly a normal flight using the QRH? How could this be our procedure?
EMB-175 Check Airman is instructed to fly a revenue trip with an aircraft that had been written up for high LP vibrations; with maintenance deferred and told to comply with QRH procedures which results in only 75% N1 in cruise.