Narrative:

We were briefed by the inbound captain that the right engine eec and elc failed during his descent. Maintenance could find nothing wrong. We had the same problem going into jac. We consulted with both dispatch and technician. A decision was made to start up and if the system worked, fine. If they did not, they were flight crew placardable. Technician told us that if one eec failed, the autothrottles would also disconnect. He advised us that in this situation, turning both eec switches off would allow the use of the autothrottles. During the takeoff, the right engine N2 oversped. I asked the first officer to concentrate on setting the right engine power. After takeoff, the right engine overtemped and oversped again. To keep the engine within limits, the power had to be reduced substantially. The engine was so difficult to control and set takeoff power, that I think we should allow the 2 system to be inoperative and the aircraft flown on MEL authority/authorized. This situation is ok on long runways, but is completely unacceptable when runway limited. Technician told us that in this situation, the engine bleed system goes into a standby mode that changes all the engine parameters. That is why they think the N2 and egt exceeded limits before EPR and N1. Cruise parameters were much reduced on the right engine. Ie, the RPM and egt were much higher than the left engine for the same power.

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Original NASA ASRS Text

Title: A B757-200 EXPERIENCED FAILURE OF THE ENG ELECTRONIC LIMIT CTL AND THE ELECTRONIC ENG CTL ON TKOF CAUSING THE #2 ENG TO OVERTEMP AND OVERSPD.

Narrative: WE WERE BRIEFED BY THE INBOUND CAPT THAT THE R ENG EEC AND ELC FAILED DURING HIS DSCNT. MAINT COULD FIND NOTHING WRONG. WE HAD THE SAME PROB GOING INTO JAC. WE CONSULTED WITH BOTH DISPATCH AND TECHNICIAN. A DECISION WAS MADE TO START UP AND IF THE SYS WORKED, FINE. IF THEY DID NOT, THEY WERE FLC PLACARDABLE. TECHNICIAN TOLD US THAT IF ONE EEC FAILED, THE AUTOTHROTTLES WOULD ALSO DISCONNECT. HE ADVISED US THAT IN THIS SIT, TURNING BOTH EEC SWITCHES OFF WOULD ALLOW THE USE OF THE AUTOTHROTTLES. DURING THE TKOF, THE R ENG N2 OVERSPED. I ASKED THE FO TO CONCENTRATE ON SETTING THE R ENG PWR. AFTER TKOF, THE R ENG OVERTEMPED AND OVERSPED AGAIN. TO KEEP THE ENG WITHIN LIMITS, THE PWR HAD TO BE REDUCED SUBSTANTIALLY. THE ENG WAS SO DIFFICULT TO CTL AND SET TKOF PWR, THAT I THINK WE SHOULD ALLOW THE 2 SYS TO BE INOP AND THE ACFT FLOWN ON MEL AUTH. THIS SIT IS OK ON LONG RWYS, BUT IS COMPLETELY UNACCEPTABLE WHEN RWY LIMITED. TECHNICIAN TOLD US THAT IN THIS SIT, THE ENG BLEED SYS GOES INTO A STANDBY MODE THAT CHANGES ALL THE ENG PARAMETERS. THAT IS WHY THEY THINK THE N2 AND EGT EXCEEDED LIMITS BEFORE EPR AND N1. CRUISE PARAMETERS WERE MUCH REDUCED ON THE R ENG. IE, THE RPM AND EGT WERE MUCH HIGHER THAN THE L ENG FOR THE SAME PWR.

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.