MD-11
Flight Crew Last 90 Days 120; Flight Crew Total 10000; Flight Crew Type 5000
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Other / Unknown
Aircraft Aircraft Damaged; General Maintenance Action
Manuals; Weather
After Type 1 deice of wings; tail and fuselage as we requested; started all three engines; placed anti-ice on due to taxiway contamination. Soon after the Number 2 Engine was stable we noted level one ENGINE 2 HI VIBRATION alert on EVM compressor indicating as high as 5.0 for 3 minutes. Completed Level One Checklist; MAINT; consequences none; with all other engine indications normal and enter level of vibration and duration in logbook. After completing checklist; we discussed a couple of options with the Mechanic on the headset. The Mechanic had mentioned there was ice fog the night before our departure that the aircraft had been exposed to all night. We would either shut down all three engines and deice the Number 2 Engine or perform a momentary 50% N1 ice clearing to shed any ice from the compressor blades. While discussing this; the EVM compressor vibration dropped to 0.4 and all other engine indications matched Number 1 and 3 engines; so we entered the write-up in the logbook and taxied out. We performed a precautionary 50% N1 momentary engine clearing on the taxi out on the Number 2 Engine and I closely monitored all engine indications on takeoff roll and everything was normal. After arrival; the mechanic called me and said 7 compressor blades were damaged and they had to borescope the engine.
After pushback and during engine start of the Number 2 engine (3rd engine to start) we received a Level 1 'ENGINE 2 VIB HI.' The aircraft had sat overnight and we were told by the Mechanic that there had been freezing fog over night and the temperature was still below freezing. We looked up the Alert in the AOM; which said 'Consequences: NONE' and it told us to log the value; duration and source. We saw vibration on the COMP as high as 5.0 but it was fluctuating to below 4.0 and back up close to 5.0 Assuming there was possibly ice on the blades; we turned the engine anti-ice on and discussed options with the Mechanic who recommended running the engine up to 50% briefly to see if it would break any ice off; we also discussed shutting down the engines and deicing again. Before we could do either; the engine vibration dropped to .4 and closely matched all engine parameters of the other two engines. We assumed the ice had broken off and with all indications normal; continued with our taxi and departure. The Captain; as pilot not flying; watched all engine indications especially close on takeoff and everything indicated normal for both the takeoff and the entire 8 plus hour flight. We wrote up the indications per the AOM in the logbook; which required maintenance to check out the engine. Maintenance found multiple damaged blades in the Compressor section on inspection. A Mechanic then called the Captain in his hotel room to inform him and discuss what had happened.
MD11 flight crew experiences 'ENGINE 2 VIB HI' during engine start. It is decided that ice may be the cause; but no action is required other than a runup. Before a runup can be accomplished the vibration ceases and the flight departs. Maintenance discovers compressor blade damage during post flight inspection.