Narrative:

Due to weight and atmospheric conditions; we were required to perform a max power; packs off takeoff from runway xxl. Our takeoff weight was 392;700 kg with payload of 90;120 kg. The initial setting of power and takeoff roll was uneventful. Per the packs off take off procedure; we had selected a distant noise abatement departure procedure. As we were climbing and the power had been reduced to climb at the flaps 5 selection; the captain motioned for me to turn on one pack and almost simultaneously with the thrust reduction and the selection of one pack on; the airframe began to vibrate. A status cue was noted on the EICAS (engine indication and crew alerting system) indication and it was also noted that the number 2 engine vibration monitor indicated 5.0 lpt (low pressure turbine). As we continued climb; the captain informed ATC we would require a level off at 7;000 feet. During the climb phase; I mentioned that the number 2 egt (exhaust gas temperature) indication was amber and reached 925 degrees C. This occurred twice. With the power in the cruise phase; the egt indicated about 40 degrees C higher than the other three engines; but never reached the amber band again. There was no yawing event or abnormal indications from any of the other three engines. We cleaned the aircraft up to clean wing state. The captain asked for vectors in the area while we sorted out the issue. The captain moved the number 2 power lever back to the idle position to see if the vibration indication would go away which it did not. The captain informed me to get dispatch on the satcom and discuss the issue we encountered. When I reached dispatch; they patched in maintenance control while I explained to them what had occurred. I then rejoined the action in the flight deck at which time I got the fuel dump checklist ready. The captain then asked me to get dispatch on the satcom once again to inform them that we would be dumping fuel and returning to ZZZ. All this time we had been on local vectors at 7;000 feet. We followed the checklist; informed center of our intent to dump fuel and we proceeded with the fuel dump of approximately 86 tons. We elected not to shut down the number 2 engine as it was still making power; no engine indications were outside of the normal range; and all flight characteristics were normal aside from the airframe vibration.after we were at an appropriate landing weight; we stopped fuel dumping and requested vectors back to ZZZ. ATC was giving us priority over other local traffic due to worsening weather conditions at ZZZ and as a result; they decided to [expedite our return] for us at which time we became an emergency aircraft. The landing at ZZZ was uneventful. We taxied off and parked at [the ramp] where we were met by a fire truck and the runway was inspected after our landing to insure there was no FOD present. After deplaning; we found that the lpt had suffered severe damage and parts of the engine had exited through the tailpipe and struck the inboard section of the flap resulting in puncture damage. There was no damage to the fan section which was indicative that something within the engine had failed and subsequently been blown through the engine. The vibration and the high egt indication was indicative of an internal failure although we had no way of verifying that information until the plane was on the ground again. I felt the entire crew did a great job maintaining flight path and altitude; running checklists; communicating with the company and ATC and landing the aircraft at the departure airport below max structural landing weight for a successful outcome from what would have eventually been engine severe damage and a mandatory shutdown.

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Original NASA ASRS Text

Title: B747-400 First Officer reported a degradation of the number two engine just after takeoff.

Narrative: Due to weight and atmospheric conditions; we were required to perform a max power; packs off takeoff from Runway XXL. Our takeoff weight was 392;700 kg with payload of 90;120 kg. The initial setting of power and takeoff roll was uneventful. Per the packs off take off procedure; we had selected a distant noise abatement departure procedure. As we were climbing and the power had been reduced to climb at the flaps 5 selection; the Captain motioned for me to turn on one pack and almost simultaneously with the thrust reduction and the selection of one pack on; the airframe began to vibrate. A status cue was noted on the EICAS (Engine Indication and Crew Alerting System) indication and it was also noted that the Number 2 engine vibration monitor indicated 5.0 LPT (Low Pressure Turbine). As we continued climb; the Captain informed ATC we would require a level off at 7;000 feet. During the climb phase; I mentioned that the Number 2 EGT (Exhaust Gas Temperature) indication was amber and reached 925 degrees C. This occurred twice. With the power in the cruise phase; the EGT indicated about 40 degrees C higher than the other three engines; but never reached the amber band again. There was no yawing event or abnormal indications from any of the other three engines. We cleaned the aircraft up to clean wing state. The Captain asked for vectors in the area while we sorted out the issue. The Captain moved the Number 2 power lever back to the idle position to see if the vibration indication would go away which it did not. The Captain informed me to get Dispatch on the SATCOM and discuss the issue we encountered. When I reached Dispatch; they patched in Maintenance Control while I explained to them what had occurred. I then rejoined the action in the flight deck at which time I got the fuel dump checklist ready. The Captain then asked me to get dispatch on the SATCOM once again to inform them that we would be dumping fuel and returning to ZZZ. All this time we had been on local vectors at 7;000 feet. We followed the checklist; informed Center of our intent to dump fuel and we proceeded with the fuel dump of approximately 86 tons. We elected not to shut down the Number 2 engine as it was still making power; no engine indications were outside of the normal range; and all flight characteristics were normal aside from the airframe vibration.After we were at an appropriate landing weight; we stopped fuel dumping and requested vectors back to ZZZ. ATC was giving us priority over other local traffic due to worsening weather conditions at ZZZ and as a result; they decided to [expedite our return] for us at which time we became an emergency aircraft. The landing at ZZZ was uneventful. We taxied off and parked at [the ramp] where we were met by a fire truck and the runway was inspected after our landing to insure there was no FOD present. After deplaning; we found that the LPT had suffered severe damage and parts of the engine had exited through the tailpipe and struck the inboard section of the flap resulting in puncture damage. There was no damage to the fan section which was indicative that something within the engine had failed and subsequently been blown through the engine. The vibration and the high EGT indication was indicative of an internal failure although we had no way of verifying that information until the plane was on the ground again. I felt the entire crew did a great job maintaining flight path and altitude; running checklists; communicating with the company and ATC and landing the aircraft at the departure airport below max structural landing weight for a successful outcome from what would have eventually been engine severe damage and a mandatory shutdown.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.