Narrative:

Air carrier aircraft, an MD88, experienced a #2 engine N1 overspd on flight. Using the engine display panel to read the recorded overspd condition, a value of 102.8% was reached. Per the MD88 maintenance manual 72-00-00-5, all inspections were performed and no deviations found. As a precaution, due to previous experience of the edp reading different than the fdr, I pulled the fdr and had the information read. The aircraft departed ZZZ on flight without incident and continued to zza on another flight, also without incident. During this time, the fdr information was read and found that the engine actually reached 103.3% N1, but also over boosted, had an egt exceedance and a fuel flow indication out of limits. The aircraft was immediately grounded and prepared for a maintenance ferry back to maintenance base on flight which included replacing the fan and hub assembly. Contributing factors were the inability of edp to provide an accurate reading with its rolling tape display and previous experience with conflicting readings of the edp and fdr. Item was discovered through a pilot report and was also found to be incomplete after fdr readout. Company policy is to trust the edp and procedure was followed as such. Pulling of the fdr was as precautionary even though it was not needed. The mistake was made in flying the aircraft before the data from the fdr was read but this is not in company policy as of this time (aug/fri/01). As far as air carrier is concerned, the edp reading is accurate and should be trusted. I do not look at it this way because of information sampling notes, but I was led to believe by 2 other sources that this information is accurate and that is why we flew the aircraft on a revenue passenger flight.

Google
 

Original NASA ASRS Text

Title: AN MD88 WAS FOUND TO HAVE #2 ENG OVERSPD, EXHAUST GAS TEMP OVER LIMITS AND FUEL FLOW OUT OF LIMITS BY READING THE FDR.

Narrative: ACR ACFT, AN MD88, EXPERIENCED A #2 ENG N1 OVERSPD ON FLT. USING THE ENG DISPLAY PANEL TO READ THE RECORDED OVERSPD CONDITION, A VALUE OF 102.8% WAS REACHED. PER THE MD88 MAINT MANUAL 72-00-00-5, ALL INSPECTIONS WERE PERFORMED AND NO DEVS FOUND. AS A PRECAUTION, DUE TO PREVIOUS EXPERIENCE OF THE EDP READING DIFFERENT THAN THE FDR, I PULLED THE FDR AND HAD THE INFO READ. THE ACFT DEPARTED ZZZ ON FLT WITHOUT INCIDENT AND CONTINUED TO ZZA ON ANOTHER FLT, ALSO WITHOUT INCIDENT. DURING THIS TIME, THE FDR INFO WAS READ AND FOUND THAT THE ENG ACTUALLY REACHED 103.3% N1, BUT ALSO OVER BOOSTED, HAD AN EGT EXCEEDANCE AND A FUEL FLOW INDICATION OUT OF LIMITS. THE ACFT WAS IMMEDIATELY GNDED AND PREPARED FOR A MAINT FERRY BACK TO MAINT BASE ON FLT WHICH INCLUDED REPLACING THE FAN AND HUB ASSEMBLY. CONTRIBUTING FACTORS WERE THE INABILITY OF EDP TO PROVIDE AN ACCURATE READING WITH ITS ROLLING TAPE DISPLAY AND PREVIOUS EXPERIENCE WITH CONFLICTING READINGS OF THE EDP AND FDR. ITEM WAS DISCOVERED THROUGH A PLT RPT AND WAS ALSO FOUND TO BE INCOMPLETE AFTER FDR READOUT. COMPANY POLICY IS TO TRUST THE EDP AND PROC WAS FOLLOWED AS SUCH. PULLING OF THE FDR WAS AS PRECAUTIONARY EVEN THOUGH IT WAS NOT NEEDED. THE MISTAKE WAS MADE IN FLYING THE ACFT BEFORE THE DATA FROM THE FDR WAS READ BUT THIS IS NOT IN COMPANY POLICY AS OF THIS TIME (AUG/FRI/01). AS FAR AS ACR IS CONCERNED, THE EDP READING IS ACCURATE AND SHOULD BE TRUSTED. I DO NOT LOOK AT IT THIS WAY BECAUSE OF INFO SAMPLING NOTES, BUT I WAS LED TO BELIEVE BY 2 OTHER SOURCES THAT THIS INFO IS ACCURATE AND THAT IS WHY WE FLEW THE ACFT ON A REVENUE PAX FLT.

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.