Narrative:

I was the captain of an medium large transport flight from ont to dfw. The aircraft had been at ont overnight in near freezing temperatures and light to moderate rain. When my first officer did the walkaround he looked at the wings noting no frost on the underside and lots of rain flowing off. He did not inspect the upper surface from a workstand and the airplane was not deiced. The airplane log book had several previous complaints about erratic indications on the left engine N1 tachometer, including one which must have occurred on takeoff, since the automatic reverse thrust had activated. We noted that several maintenance efforts had not corrected the problem. We made the takeoff using maximum power with engine anti-ice on due to the RAT of 4-5 degrees C and light rain falling. At about 40-50 KTS the art activated with no abnormal engine indications. We agreed that the engines looked ok and continued the takeoff. Right after liftoff the left N1 gauge became very erratic and soon went to 0, but everything else was ok. This confirmed our suspicion that all we had was an indicator problem. The engine noise seemed louder than normal and sounded as if the engines were out of sync. I had disconnected the autothrottles after takeoff to reduce power from reserve to maximum, but small changes in relative EPR setting did not change the noise. When I leveled off at 7000' and reduced power, the noise became normal. At that time a F/a came into the cockpit to report a lot of noise and vibration in the aft cabin, and it was clear that she was quite upset. Since we were in the middle of our departure, in icing conditions and very busy, we continued on until the climb checklist was done. I then sent the first officer aft to check. He confirmed that there was excessive noise and vibration from the left engine, so I decided to return to ont. My dispatcher asked us to consider lax for its maintenance capability, and we continued there west/O further incident. Both engines were found to have considerable FOD to the fan blades, requiring one engine change and a lot of new blades in the other. The F/a told me that the noise and vibration had begun very early in the takeoff roll and that 2 passenger had told her of seeing sheets of ice about 1/8' thick coming off the wing surface on takeoff rotation and initial climb. I think that what we were dealing with was 2 unrelated problems, both concerning the engines. Perhaps the N1 gauge and art problem misled us or distracted us from recognizing the real problem: the rotor damage to both engines. My initial reaction was that since the conditions were just right that morning for upper wing clear ice formation, and since the airplane was refueled just before preflight inspection, then the ice must have been ingested on takeoff. The F/a report, however, suggests that the engine(south) might well have had prior damage. If the engines had been damaged before our flight, they may not have been run at a high enough RPM for noise and vibration to have alerted that crew. The medium large transport has received much attention lately on this subject, but the problem has clearly not been fully solved. Supplemental information from acn 103931: the medium large transport has a phenomenon of clear ice forming on top of the wings after refueling when cold fuel comes in contact with underside of the top of the wing with visible moisture present. This occurs even at temperatures well above freezing. Were the engines damaged the night before?

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Original NASA ASRS Text

Title: ACR MLG ENGINE DAMAGE FROM ICE INGESTION DURING TKOF FROM ONT. DIVERSION TO ALTERNATE.

Narrative: I WAS THE CAPT OF AN MLG FLT FROM ONT TO DFW. THE ACFT HAD BEEN AT ONT OVERNIGHT IN NEAR FREEZING TEMPS AND LIGHT TO MODERATE RAIN. WHEN MY F/O DID THE WALKAROUND HE LOOKED AT THE WINGS NOTING NO FROST ON THE UNDERSIDE AND LOTS OF RAIN FLOWING OFF. HE DID NOT INSPECT THE UPPER SURFACE FROM A WORKSTAND AND THE AIRPLANE WAS NOT DEICED. THE AIRPLANE LOG BOOK HAD SEVERAL PREVIOUS COMPLAINTS ABOUT ERRATIC INDICATIONS ON THE LEFT ENG N1 TACHOMETER, INCLUDING ONE WHICH MUST HAVE OCCURRED ON TKOF, SINCE THE AUTO REVERSE THRUST HAD ACTIVATED. WE NOTED THAT SEVERAL MAINT EFFORTS HAD NOT CORRECTED THE PROB. WE MADE THE TKOF USING MAX PWR WITH ENG ANTI-ICE ON DUE TO THE RAT OF 4-5 DEGS C AND LIGHT RAIN FALLING. AT ABOUT 40-50 KTS THE ART ACTIVATED WITH NO ABNORMAL ENG INDICATIONS. WE AGREED THAT THE ENGS LOOKED OK AND CONTINUED THE TKOF. RIGHT AFTER LIFTOFF THE LEFT N1 GAUGE BECAME VERY ERRATIC AND SOON WENT TO 0, BUT EVERYTHING ELSE WAS OK. THIS CONFIRMED OUR SUSPICION THAT ALL WE HAD WAS AN INDICATOR PROB. THE ENG NOISE SEEMED LOUDER THAN NORMAL AND SOUNDED AS IF THE ENGS WERE OUT OF SYNC. I HAD DISCONNECTED THE AUTOTHROTTLES AFTER TKOF TO REDUCE PWR FROM RESERVE TO MAX, BUT SMALL CHANGES IN RELATIVE EPR SETTING DID NOT CHANGE THE NOISE. WHEN I LEVELED OFF AT 7000' AND REDUCED PWR, THE NOISE BECAME NORMAL. AT THAT TIME A F/A CAME INTO THE COCKPIT TO RPT A LOT OF NOISE AND VIBRATION IN THE AFT CABIN, AND IT WAS CLEAR THAT SHE WAS QUITE UPSET. SINCE WE WERE IN THE MIDDLE OF OUR DEP, IN ICING CONDITIONS AND VERY BUSY, WE CONTINUED ON UNTIL THE CLB CHKLIST WAS DONE. I THEN SENT THE F/O AFT TO CHK. HE CONFIRMED THAT THERE WAS EXCESSIVE NOISE AND VIBRATION FROM THE LEFT ENG, SO I DECIDED TO RETURN TO ONT. MY DISPATCHER ASKED US TO CONSIDER LAX FOR ITS MAINT CAPABILITY, AND WE CONTINUED THERE W/O FURTHER INCIDENT. BOTH ENGS WERE FOUND TO HAVE CONSIDERABLE FOD TO THE FAN BLADES, REQUIRING ONE ENG CHANGE AND A LOT OF NEW BLADES IN THE OTHER. THE F/A TOLD ME THAT THE NOISE AND VIBRATION HAD BEGUN VERY EARLY IN THE TKOF ROLL AND THAT 2 PAX HAD TOLD HER OF SEEING SHEETS OF ICE ABOUT 1/8' THICK COMING OFF THE WING SURFACE ON TKOF ROTATION AND INITIAL CLB. I THINK THAT WHAT WE WERE DEALING WITH WAS 2 UNRELATED PROBS, BOTH CONCERNING THE ENGS. PERHAPS THE N1 GAUGE AND ART PROB MISLED US OR DISTRACTED US FROM RECOGNIZING THE REAL PROB: THE ROTOR DAMAGE TO BOTH ENGS. MY INITIAL REACTION WAS THAT SINCE THE CONDITIONS WERE JUST RIGHT THAT MORNING FOR UPPER WING CLEAR ICE FORMATION, AND SINCE THE AIRPLANE WAS REFUELED JUST BEFORE PREFLT INSPECTION, THEN THE ICE MUST HAVE BEEN INGESTED ON TKOF. THE F/A RPT, HOWEVER, SUGGESTS THAT THE ENG(S) MIGHT WELL HAVE HAD PRIOR DAMAGE. IF THE ENGS HAD BEEN DAMAGED BEFORE OUR FLT, THEY MAY NOT HAVE BEEN RUN AT A HIGH ENOUGH RPM FOR NOISE AND VIBRATION TO HAVE ALERTED THAT CREW. THE MLG HAS RECEIVED MUCH ATTN LATELY ON THIS SUBJECT, BUT THE PROB HAS CLEARLY NOT BEEN FULLY SOLVED. SUPPLEMENTAL INFO FROM ACN 103931: THE MLG HAS A PHENOMENON OF CLEAR ICE FORMING ON TOP OF THE WINGS AFTER REFUELING WHEN COLD FUEL COMES IN CONTACT WITH UNDERSIDE OF THE TOP OF THE WING WITH VISIBLE MOISTURE PRESENT. THIS OCCURS EVEN AT TEMPS WELL ABOVE FREEZING. WERE THE ENGS DAMAGED THE NIGHT BEFORE?

Data retrieved from NASA's ASRS site as of August 2007 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.