AN FO REPORTS AN MD-80 WAS OPERATED FOR SIX WEEKS OR LONGER WITH A LEFT ENG THAT COULD NOT PRODUCE RATED THRUST WITHIN THE CERTIFICATE LIMITS. PILOTS NEEDED TO RETARD LEFT THROTTLE AFTER LIFTOFF TO REDUCE EGT.

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I WOULD LIKE TO REPORT AN ACFT MAINT ISSUE THAT I BELIEVE SHOULD BE BROUGHT TO THE ATTENTION OF FLT OPS TRAINING; SAFETY; AND MAINT QUALITY ASSURANCE. WE WERE PRESENTED WITH ACFT X AT ZZZ. THE INBOUND CREW COMMENTED WITHOUT ELABORATION; 'THE LEFT ENG RUNS A LITTLE HOT.' ON TKOF THE LEFT ENG EGT WAS HOTTER THAN THE RIGHT. AT ROTATION THE EGT SHOWED 610 DEGS. I WAS THE PF; HOWEVER; THE CAPT ELECTED TO PULL THE THROTTLE BACK SHORTLY AFTER LIFTOFF TO REDUCE THE EGT TO THE 590 DEG LIMIT FOR MAX THRUST. THIS RESULTED IN A SUBSTANTIAL DECREASE BELOW THE TKOF EPR SETTING. THE TKOF AND REMINDER OF THE FLT WAS UNEVENTFUL AND THE ENG OPERATED WITHIN LIMITS THEREAFTER; HOWEVER; EGT WAS ABOUT 30 DEGS HIGHER THAN THE RIGHT ENG IN ALL PHASES OF FLT. A SUBSEQUENT REVIEW OF ALL AVAILABLE LOGBOOK PAGES AVAILABLE; REVEALED THIS TO BE AN ONGOING PROBLEM WITH THIS ENG -- IN FACT; THERE WERE REPEATED DISCREPANCY REPORTS DATING TO AS EARLY AS LAST MONTH. WE THEN SUBSEQUENTLY REPORTED THE HIGH TEMP IN THE LOGBOOK; ALONG WITH RELATED PARAMETERS; PRIOR TO LNDG AT ZZZ1. AS A RESULT THE AIRPLANE WAS REMOVED FROM SVC AND THE ENG CHANGED. HERE ARE THE PERTINENT FACTS: THE OVERLIMIT EGT WAS REPORTED IN THE LOGBOOK AT LEAST 4 TIMES BETWEEN LAST MONTH AND THE DATE IT WAS FINALLY CORRECTED BY ENG REPLACEMENT. THE CORRECTIVE ACTIONS TAKEN (BLEED SYSTEM REPAIRS; EGT INDICATOR CHANGE; COMPRESSOR WASHING) WERE CLEARLY INEFFECTIVE; SINCE THE DISCREPANCY REPEATED. THERE DID NOT APPEAR TO BE ANY ATTEMPT BY MAINT; FOLLOWING EACH REPAIR; TO USE A GND POWER RUN TO DETERMINE THE EFFICIENCY OF THE REPAIRS; OR WHETHER OR NOT THE ENG PRODUCED RATED THRUST WITHIN LIMITS PRIOR TO RETURNING THE AIRPLANE TO SVC. ONLY 4 FLT CREWS MADE DISCREPANCY REPORTS OVER THE SIX-WEEK PERIOD; EVEN THOUGH THERE MUST HAVE BEEN MANY MORE TAKEOFFS WHERE THE 590 LIMIT WAS EXCEEDED. THE ACFT MAINT HISTORY FILES EVEN SHOWED ONE EGT EXCEEDANCE OF 640 DEGS; ALTHOUGH THIS WAS NOT IN THE LOGBOOK. I DO NOT THINK THAT A THRUST REDUCTION DURING THE TKOF PATH FOR HIGH EGT IS JUSTIFIED UNLESS AN ENG IS EXCEEDING 630 DEGS. OBSTACLE CLRNC COULD BE IN DOUBT IF THE OPPOSITE ENG FAILS. THE ONLY GERMANE GUIDANCE PROVIDED TO FLT CREWS IN THE OPS MANUAL IS QRH PAGE ENG 22 AND THE CAPT WAS NOT FAMILIAR WITH IT. THE PAGE CONSISTS OF A RATHER AMBIGUOUS TABLE OF VALUES; BUT IT DOES SUGGEST THAT ENG SHUTDOWN OR EARLY LNDG IS NOT JUSTIFIED UNLESS THE EGT EXCEEDS 645 DEGS. IT IS MY UNDERSTANDING THAT THE EGT AND RPM LIMITS FOR MAX THRUST ARE SET FORTH IN THE AFM TO PROVIDE A MEANS FOR CREWS TO RECOGNIZE ENG DETERIORATION. THIS ALSO ENSURES THAT RESERVE THRUST CAN BE PRODUCED WITHIN LIMITS IF REQUIRED IN AN EMER. HOWEVER; IT IS EVIDENT THAT THIS AIRPLANE WAS OPERATED FOR 6 WEEKS OR LONGER WITH AN ENG THAT COULD NOT PRODUCE RATED THRUST WITHIN THE CERTIFICATE LIMITS. BASED UPON THE RECORD; NEITHER MAINT OR FLT CREWS SEEMED TO APPRECIATE THE SIGNIFICANCE OF THIS. THE ENG MIGHT NOT HAVE BEEN CAPABLE OF DELIVERING THE REQUIRED THRUST HAD THE OPPOSITE ENG FAILED. FURTHERMORE; ANY USE OF THE REVERSE THRUST -- ARTS ACTIVATION FOR WINDSHEAR -- WOULD HAVE CERTAINLY CAUSED THE EGT AND RPM TO EXCEED THE ULTIMATE LIMITS. WE NEED TO HAVE FLT OPS PROCS AND TRAINING SET FORTH FOR VARIOUS ENG MALFUNCTIONS DURING THE TAKEOFF PATH; INCLUDING EGT AND RPM EXCURSIONS; AND AN EXPLANATION OF THE PURPOSE OF THE EGT AND RPM LIMITS. AND OUR MAINT QA GROUP NEEDS TO ENSURE THAT OUR COMPANY IS ABLE TO RECOGNIZE AND CORRECT ENG THRUST DETERIORATION BEFORE IT RESULTS IN AN INCIDENT OR ENG FAILURE.