Narrative:

As the VNAV retarded throttles, the right engine accelerated to 98 percent N1. Disconnected autothrottles. Left engine responded normally, but right remained at 98 percent. Found it was impossible to descend, much less keep airplane below redline, so elected to shut it down. Performed normal single engine procedures as we continued to descend to make crossing restrictions. All the above happened just as we were being turned over to approach from center. Made the crossing and speed restriction ok. At first we thought #1 had failed. Speed got up to redline due to high power of #2. Before deciding to shut down, decided to test throttle response on both engines, before shutting 1 down. There is no procedure in the book for an accelerated engine. With that in mind, it would have been very easy to shut down the ctlable engine if both throttles hadn't been tested. Also, found you can't descend an medium large transport with full power on 1, clean, without going to redline. Suggest that FAA and engine manufacturers look into problem of accelerating engines. We understand this problem is not uncommon. Also suggest an appropriate procedure be developed for inclusion in training syllabus and emergency procedures. Remainder of flight, ILS, and landing was normal. Declared emergency as a precaution, so to have the equipment standing by. Callback conversation with reporter revealed the following information: the reporting first officer states that maintenance found a broken cable to the right engine. There was no resistance at all to the throttle movement, and no response from the engine. The engine stayed at cruise power until shut down. Supplemental information from acn 234664: this was 1 situation where the dead foot, bad engine logic was not true and could have led to shutting down the good engine. Of course, this would not be a problem in this situation, unless it would not relight.

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Original NASA ASRS Text

Title: AN ACR MLG LOST CTL OF 1 OF ITS ENGS. IT WOULD NOT COME OUT OF CRUISE PWR.

Narrative: AS THE VNAV RETARDED THROTTLES, THE R ENG ACCELERATED TO 98 PERCENT N1. DISCONNECTED AUTOTHROTTLES. L ENG RESPONDED NORMALLY, BUT R REMAINED AT 98 PERCENT. FOUND IT WAS IMPOSSIBLE TO DSND, MUCH LESS KEEP AIRPLANE BELOW REDLINE, SO ELECTED TO SHUT IT DOWN. PERFORMED NORMAL SINGLE ENG PROCS AS WE CONTINUED TO DSND TO MAKE XING RESTRICTIONS. ALL THE ABOVE HAPPENED JUST AS WE WERE BEING TURNED OVER TO APCH FROM CTR. MADE THE XING AND SPD RESTRICTION OK. AT FIRST WE THOUGHT #1 HAD FAILED. SPD GOT UP TO REDLINE DUE TO HIGH PWR OF #2. BEFORE DECIDING TO SHUT DOWN, DECIDED TO TEST THROTTLE RESPONSE ON BOTH ENGS, BEFORE SHUTTING 1 DOWN. THERE IS NO PROC IN THE BOOK FOR AN ACCELERATED ENG. WITH THAT IN MIND, IT WOULD HAVE BEEN VERY EASY TO SHUT DOWN THE CTLABLE ENG IF BOTH THROTTLES HADN'T BEEN TESTED. ALSO, FOUND YOU CAN'T DSND AN MLG WITH FULL PWR ON 1, CLEAN, WITHOUT GOING TO REDLINE. SUGGEST THAT FAA AND ENG MANUFACTURERS LOOK INTO PROB OF ACCELERATING ENGS. WE UNDERSTAND THIS PROB IS NOT UNCOMMON. ALSO SUGGEST AN APPROPRIATE PROC BE DEVELOPED FOR INCLUSION IN TRAINING SYLLABUS AND EMER PROCS. REMAINDER OF FLT, ILS, AND LNDG WAS NORMAL. DECLARED EMER AS A PRECAUTION, SO TO HAVE THE EQUIP STANDING BY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTING FO STATES THAT MAINT FOUND A BROKEN CABLE TO THE R ENG. THERE WAS NO RESISTANCE AT ALL TO THE THROTTLE MOVEMENT, AND NO RESPONSE FROM THE ENG. THE ENG STAYED AT CRUISE PWR UNTIL SHUT DOWN. SUPPLEMENTAL INFO FROM ACN 234664: THIS WAS 1 SIT WHERE THE DEAD FOOT, BAD ENG LOGIC WAS NOT TRUE AND COULD HAVE LED TO SHUTTING DOWN THE GOOD ENG. OF COURSE, THIS WOULD NOT BE A PROB IN THIS SIT, UNLESS IT WOULD NOT RELIGHT.

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.