Narrative:

In denver, at the gate, during the initial brief, I asked the first officer to fly the leg to indianapolis as I would normally ask so that I may observe the pilot and allow me the opportunity to assess as an in-flight manager, having this been the first leg with a new crew at the beginning of the month. The climb check was completed and we were en route to indianapolis. ATC gave instructions to climb FL290 and we held there for a period of time for crossing traffic. At about 180 mi or so from denver, I quickly noticed while level at FL290 that the #2 engine thrust reverser unlock light came on. I told the first officer that he had the radios and to continue to fly the aircraft. At that point, he was on autoplt B at altitude hold. He complied and I pulled out the QRH and went to the checklist for reverse unlocked light (in-flight). I ran the entire checklist with interactive discussion with the first officer that the thrust lever was not restr at any point and the overhead reverser isolation valve light was not on. I called back to the 'a' flight attendant to check if he noticed anything out of the ordinary on the #2 engine and he stated that all looked normal. All engine indications appeared normal and based on the fact that no other indications but reverser unlock light were on, I believe it to be as the QRH states, 'the light is giving a false indication.' to further my problem solving, I elected to call back to maintenance control and dispatch and told them of our disposition and that I was contemplating on returning to denver for this condition. During the discussion with maintenance, I pulled out the MEL and looked at the requirements to MEL a reverser unlock light. The book stated that maintenance would lock out the reverser on the ground and add the MEL to the release, which in this case would be the next flight. Maintenance control opted that I continue to indianapolis. An air carrier maintenance mechanic would meet me at the gate and lockout the #2 engine thrust reverser. Somewhere between FL180 and descending to 11000 ft, we felt a vibration in the control column and I immediately went into sterile with the passenger. The routing to change the power setting that seemed to be creating a vibration that could be felt in the cockpit center console. I told the first officer he had the aircraft and radios as I reached for the QRH. At first I felt the thrust reverser starting to open, so I quickly analyzed the engine gauges and all indicated normal. I repeated this for both the engine and hydraulics system. I continued to evaluate the problem. I pushed the #2 engine throttle slowly forward and found that to be at 60% N2. An extreme vibration now rattled the aircraft much more than previously. I quickly brought the thrust lever back to idle and noted the engine instruments normal. I felt the reverser at that time could be partly open or the engine was failing. The thrust lever never showed signs that it was restr. I quickly discussed with the first officer the possibility of preventive engine shutdown and to configure early using flap 15 degrees. I then called back for the flight attendants to be seated. I left the #2 engine throttle at idle and elected to keep it running and carried the memory item of engine limit. The landing was uneventful and both thrust reversers were used. The first officer called out distance remaining until we came to a stop. The engine vibration was felt on the ground when the #2 engine thrust reverser was deployed, however, the indications were once again normal. I then met the mechanic waiting at the jetway who was there to lock out the #2 engine thrust reverser and told him of what we had just experienced. He went out to look at the engine as the outbound crew started to come down the jetway. After inspection, the mechanic stated the engine had metal pieces in the tailpipe and that he tried to rotate the fan and after several tries the fan froze up. At that point, he reported that the aircraft was not airworthy and suspected engine failure. I then spoke to maintenance control after the mechanic told them about the engine failing. I also wrote up the first officer's navigation radios for the loss of his radio at localizer capture. Callback conversation with reporter revealed the following information: the reporter stated the cause of the #2 engine vibration was the failure of the turbine section. The reporter said turbine parts were picked out of the tailpipe and it determined an engine change was required. The reporter stated during the part of the flight when the engine was run at idle all indications were normal.

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Original NASA ASRS Text

Title: A B737-200 ON DSCNT BTWN FL180 AND 11000 FT, A #2 ENG VIBRATION WAS FELT. ENG OPERATED AT IDLE FOR LNDG. MAINT FOUND TURBINE PARTS IN TAILPIPE.

Narrative: IN DENVER, AT THE GATE, DURING THE INITIAL BRIEF, I ASKED THE FO TO FLY THE LEG TO INDIANAPOLIS AS I WOULD NORMALLY ASK SO THAT I MAY OBSERVE THE PLT AND ALLOW ME THE OPPORTUNITY TO ASSESS AS AN INFLT MGR, HAVING THIS BEEN THE FIRST LEG WITH A NEW CREW AT THE BEGINNING OF THE MONTH. THE CLB CHK WAS COMPLETED AND WE WERE ENRTE TO INDIANAPOLIS. ATC GAVE INSTRUCTIONS TO CLB FL290 AND WE HELD THERE FOR A PERIOD OF TIME FOR XING TFC. AT ABOUT 180 MI OR SO FROM DENVER, I QUICKLY NOTICED WHILE LEVEL AT FL290 THAT THE #2 ENG THRUST REVERSER UNLOCK LIGHT CAME ON. I TOLD THE FO THAT HE HAD THE RADIOS AND TO CONTINUE TO FLY THE ACFT. AT THAT POINT, HE WAS ON AUTOPLT B AT ALT HOLD. HE COMPLIED AND I PULLED OUT THE QRH AND WENT TO THE CHKLIST FOR REVERSE UNLOCKED LIGHT (INFLT). I RAN THE ENTIRE CHKLIST WITH INTERACTIVE DISCUSSION WITH THE FO THAT THE THRUST LEVER WAS NOT RESTR AT ANY POINT AND THE OVERHEAD REVERSER ISOLATION VALVE LIGHT WAS NOT ON. I CALLED BACK TO THE 'A' FLT ATTENDANT TO CHK IF HE NOTICED ANYTHING OUT OF THE ORDINARY ON THE #2 ENG AND HE STATED THAT ALL LOOKED NORMAL. ALL ENG INDICATIONS APPEARED NORMAL AND BASED ON THE FACT THAT NO OTHER INDICATIONS BUT REVERSER UNLOCK LIGHT WERE ON, I BELIEVE IT TO BE AS THE QRH STATES, 'THE LIGHT IS GIVING A FALSE INDICATION.' TO FURTHER MY PROB SOLVING, I ELECTED TO CALL BACK TO MAINT CTL AND DISPATCH AND TOLD THEM OF OUR DISPOSITION AND THAT I WAS CONTEMPLATING ON RETURNING TO DENVER FOR THIS CONDITION. DURING THE DISCUSSION WITH MAINT, I PULLED OUT THE MEL AND LOOKED AT THE REQUIREMENTS TO MEL A REVERSER UNLOCK LIGHT. THE BOOK STATED THAT MAINT WOULD LOCK OUT THE REVERSER ON THE GND AND ADD THE MEL TO THE RELEASE, WHICH IN THIS CASE WOULD BE THE NEXT FLT. MAINT CTL OPTED THAT I CONTINUE TO INDIANAPOLIS. AN ACR MAINT MECH WOULD MEET ME AT THE GATE AND LOCKOUT THE #2 ENG THRUST REVERSER. SOMEWHERE BTWN FL180 AND DSNDING TO 11000 FT, WE FELT A VIBRATION IN THE CTL COLUMN AND I IMMEDIATELY WENT INTO STERILE WITH THE PAX. THE RTING TO CHANGE THE PWR SETTING THAT SEEMED TO BE CREATING A VIBRATION THAT COULD BE FELT IN THE COCKPIT CTR CONSOLE. I TOLD THE FO HE HAD THE ACFT AND RADIOS AS I REACHED FOR THE QRH. AT FIRST I FELT THE THRUST REVERSER STARTING TO OPEN, SO I QUICKLY ANALYZED THE ENG GAUGES AND ALL INDICATED NORMAL. I REPEATED THIS FOR BOTH THE ENG AND HYDS SYS. I CONTINUED TO EVALUATE THE PROB. I PUSHED THE #2 ENG THROTTLE SLOWLY FORWARD AND FOUND THAT TO BE AT 60% N2. AN EXTREME VIBRATION NOW RATTLED THE ACFT MUCH MORE THAN PREVIOUSLY. I QUICKLY BROUGHT THE THRUST LEVER BACK TO IDLE AND NOTED THE ENG INSTS NORMAL. I FELT THE REVERSER AT THAT TIME COULD BE PARTLY OPEN OR THE ENG WAS FAILING. THE THRUST LEVER NEVER SHOWED SIGNS THAT IT WAS RESTR. I QUICKLY DISCUSSED WITH THE FO THE POSSIBILITY OF PREVENTIVE ENG SHUTDOWN AND TO CONFIGURE EARLY USING FLAP 15 DEGS. I THEN CALLED BACK FOR THE FLT ATTENDANTS TO BE SEATED. I LEFT THE #2 ENG THROTTLE AT IDLE AND ELECTED TO KEEP IT RUNNING AND CARRIED THE MEMORY ITEM OF ENG LIMIT. THE LNDG WAS UNEVENTFUL AND BOTH THRUST REVERSERS WERE USED. THE FO CALLED OUT DISTANCE REMAINING UNTIL WE CAME TO A STOP. THE ENG VIBRATION WAS FELT ON THE GND WHEN THE #2 ENG THRUST REVERSER WAS DEPLOYED, HOWEVER, THE INDICATIONS WERE ONCE AGAIN NORMAL. I THEN MET THE MECH WAITING AT THE JETWAY WHO WAS THERE TO LOCK OUT THE #2 ENG THRUST REVERSER AND TOLD HIM OF WHAT WE HAD JUST EXPERIENCED. HE WENT OUT TO LOOK AT THE ENG AS THE OUTBOUND CREW STARTED TO COME DOWN THE JETWAY. AFTER INSPECTION, THE MECH STATED THE ENG HAD METAL PIECES IN THE TAILPIPE AND THAT HE TRIED TO ROTATE THE FAN AND AFTER SEVERAL TRIES THE FAN FROZE UP. AT THAT POINT, HE RPTED THAT THE ACFT WAS NOT AIRWORTHY AND SUSPECTED ENG FAILURE. I THEN SPOKE TO MAINT CTL AFTER THE MECH TOLD THEM ABOUT THE ENG FAILING. I ALSO WROTE UP THE FO'S NAV RADIOS FOR THE LOSS OF HIS RADIO AT LOC CAPTURE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE #2 ENG VIBRATION WAS THE FAILURE OF THE TURBINE SECTION. THE RPTR SAID TURBINE PARTS WERE PICKED OUT OF THE TAILPIPE AND IT DETERMINED AN ENG CHANGE WAS REQUIRED. THE RPTR STATED DURING THE PART OF THE FLT WHEN THE ENG WAS RUN AT IDLE ALL INDICATIONS WERE NORMAL.

Data retrieved from NASA's ASRS site as of July 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.