ACFT EQUIP PROB. ENG OVERSPD.

Narrative

PREFLT; TAXI AND TKOF ROLL (MAX EPR SELECTED) WERE NORMAL UNTIL AUTOTHROTTLE ENGAGEMENT. AT APPROX 75 PERCENT N1 CAPT CALLED FOR AUTOTHROTTLES (CAPT FLYING). TARGET N1 EPR FOR TKOF WAS 114 PERCENT N1. AUTOTHROTTLES ADVANCED FASTER THAN NORMAL AND SET ENG #1 108 PERCENT; ENG #2 114 PERCENT; ENG #3 109 PERCENT. V1 WAS APPROX 162 KTS. #2 EGT WAS RISING RAPIDLY AND QUICKLY EXCEEDED ITS LIMIT OF 960 DEGS CELSIUS. PWR WAS REDUCED WHEN #2 EGT REACHED 980 DEGS CELSIUS; STILL RISING AT THE CAPT'S DIRECTION. WHILE REDUCING #2 PWR TO REDUCE THE EGT; #1 ENG OVERTEMP LIGHT ILLUMINATED. ITS EGT HAD EXCEEDED 960 DEGS CELSIUS (ENG LIMIT) TO APPROX 980 DEGS; STILL RISING. AT THAT TIME WE HAD PASSED V1 AND WERE APCHING ROTATION. DURING ROTATION; ENG #3 OVERSPD WARNING LIGHT ILLUMINATED AND ENG #3 N2 INDICATED 114 PERCENT (LIMIT 110 PERCENT). GEAR RETRACTION WAS CALLED FOR AND ACCOMPLISHED. ALL ENGS WERE RECHKED BELOW MINIMUM TKOF EPR PRIOR TO NORMAL REDUCTION TO CLB PWR. THIS ALLOWED ALL ENGS TO OPERATE IN THEIR NORMAL RANGE. MAINT IAH WAS CONSULTED VIA ARINC (THE FLT WAS IAH TO ORY) AND ADVISED OF THE ABOVE LISTED OCCURRENCE IN DETAIL. DISPATCH AND MAINT REQUESTED THE ACFT BE FLOWN TO EWR WHERE A REPLACEMENT ENG WAS AVAILABLE FOR ENG #3. THE CREW AFTER A VERY EXCELLENT COCKPIT RESOURCE MGMNT DISCUSSION; DUMPED FUEL TO LNDG GROSS WT AND RETURNED TO IAH. IT IS SEVERAL DAYS AFTER THIS OCCURRENCE. LAST EVENING THE CAPT ADVISED ME ALL ENG INSTS HAVE BEEN DETERMINED TO HAVE BEEN WORKING NORMALLY. NO REASON HAS BEEN DETERMINED FOR THE #3 ENG N2 OVERSPD WHICH HAS MULTIPLE SYS TO PREVENT THIS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE #3 ENG WAS TORN DOWN WITH NO DAMAGE; NOR IDENTIFIABLE PROB. ENG MANUFACTURER SAID IT WAS A GAUGE PROB AND THE GAUGE MANUFACTURER SAID IT WAS ENG PROB. RPTR SAYS THAT HIS COMPANY HAS ENG OVERTEMPS REGULARLY AND REGARDLESS OF ACFT TYPE; PROBABLY DUE TO HIGH TEMPS ASSOCIATED WITH SOME OF THE ARPTS WHERE THEY OPERATE. CONSEQUENTLY; SMALL OVERTEMPS ARE NOT UNUSUAL AND FLCS BECOME SOMEWHAT CASUAL ABOUT THEM. THE MANUFACTURER'S ENGS HAVE WHAT IS CALLED 'BLOOM AND DROOP' WHICH RELATES TO EXPANDING AND CONTRACTING OF TURBINE BLADES DURING TKOF PWR APPLICATION. AT 80 KTS THE PWR MUST BE SET IN DETENT OR A 'CLAM' FUNCTION MAY AFFECT CORRECT THRUST OUTPUT. IN THIS CASE; SINCE ALL ENGS WERE AFFECTED; IT COULD HAVE BEEN SOMETHING LIKE THIS OR MORE LIKELY AN AUTOTHROTTLE MALFUNCTION. THE RPTR'S COMPANY MAINT WANTED THE FLC TO FERRY ACFT TO DISTANT ARPT FOR ENG REPAIR; BUT THE FLC REFUSED.