Narrative:

A normal preflight was completed. The logbook review showed one deferred item had been cleared by oak maintenance the previous evening -- a problem with the left reverser. The maintenance release document appeared complete and acceptable. Taxi and preparation for takeoff were normal. The first officer was the PF. When cleared for takeoff, he stood the throttles up, waited for engines to stabilize, advanced throttles toward r-to power, and called for me to push the EPR switch to engage the autothrottle. Power settings for the reduced power takeoff were 1.33 EPR and a xref of 83 percent N1. The autothrottle moved the thrust on the left engine to 1.32 EPR and between 81-82 percent N1. I checked the EPR and N1 on both engines, checked the airspeed on both sides and announced 90 KTS. I took a quick glance outside and then rechked the engine gauges. The left was still slightly low but within normal limits for autothrottle setting at 1.32 EPR and now about 82 percent N1. Instead of just lightly monitoring the autothrottle and guarding the throttles, I attempted to actively 'tweak' the left throttle. The throttle moved very slightly forward and hit a mechanical stop approximately 2 - 2 1/2 inches short of full travel. The aircraft was now well into the high speed regime of the takeoff and acceleration was normal. Given those 2 factors and the predep briefing that short of an engine failure, fire, or reverser unlocked, we will continue any takeoff from high speed unless it seems that the aircraft will not fly, I elected to continue the takeoff. Out of 3000 ft following the after takeoff checklist, I began to more actively attempt to identify the cause of the problem. I checked the reverse level down, checked for any circuit breakers popped, and retarded the throttle slightly and attempted to push it forward again. It hit the same mechanical stop. Interestingly, during the climb as the climb EPR increased, so did the actual indicated EPR remaining about 0.01 below what was called for by the thrust management computer. I told the first officer I thought we had a problem. He checked the same things I did and we began to discuss our options. He expressed concern about single altitude driftdown over the mountains if the right engine should quit en route. I offered that we might use a B737 technique of having driftdown alternates for each segment of the flight if the WX was acceptable. We called dispatch and began to discuss our problem and requested information about the WX at acceptable en route alternates. I became concerned, not about the driftdown and landing, but about the possibility of a single engine go around at a high altitude airport versus a reduced power takeoff at sea level. We asked dispatch to connect us with system aircraft maintenance control. We discussed our problem and asked his opinion about what thrust we could expect from the left engine given our situation. He stated what we already expected, that there was no way to know. He recommended that we return to the bay area for an engine check. We concurred and advised dispatch that with their blessing we would return to sfo in order to have better passenger options and better parts availability. We landed normally at sfo. Subsequent maintenance inspection of the engine revealed that in working on the reverser the evening before, the mechanic had pulled a circuit breaker in the cockpit and safetied it with an orange collar. A collared breaker to a pilot indicates that maintenance has taken appropriate action and is not a concern, especially given a clean maintenance release document, no warning lights, and no EICAS warnings, advisories, or cautions. My recommended solution is first, engineering identify all circuit breakers that would potentially pose this kind of problem -- that is, pulling the circuit breaker could adversely affect the flight but give no crew warning. Second, maintenance should be required to post an orange or red 'no fly' placard on the control wheel or stick any time one of these circuit breakers is used as a safety for their work until the circuit breakers have been reset.

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Original NASA ASRS Text

Title: B757 ACFT ON TKOF AND CLB THE #2 ENG EPR REMAINED LOW AND THE THROTTLE WOULD NOT ADVANCE TO FULL TRAVEL. FLC DISCUSSED THE PROB, CALLED THEIR COMPANY MAINT AND IT WAS DETERMINED TO DIVERT TO A CLOSE ARPT FOR REPAIR. POSTFLT INSPECTION FOUND A CIRCUIT BREAKER PULLED AND COLLARED AS A RESULT OF PREVIOUS MAINT WHICH WAS THE CAUSE OF THE ENG FAULT.

Narrative: A NORMAL PREFLT WAS COMPLETED. THE LOGBOOK REVIEW SHOWED ONE DEFERRED ITEM HAD BEEN CLRED BY OAK MAINT THE PREVIOUS EVENING -- A PROB WITH THE L REVERSER. THE MAINT RELEASE DOCUMENT APPEARED COMPLETE AND ACCEPTABLE. TAXI AND PREPARATION FOR TKOF WERE NORMAL. THE FO WAS THE PF. WHEN CLRED FOR TKOF, HE STOOD THE THROTTLES UP, WAITED FOR ENGS TO STABILIZE, ADVANCED THROTTLES TOWARD R-TO PWR, AND CALLED FOR ME TO PUSH THE EPR SWITCH TO ENGAGE THE AUTOTHROTTLE. PWR SETTINGS FOR THE REDUCED PWR TKOF WERE 1.33 EPR AND A XREF OF 83 PERCENT N1. THE AUTOTHROTTLE MOVED THE THRUST ON THE L ENG TO 1.32 EPR AND BTWN 81-82 PERCENT N1. I CHKED THE EPR AND N1 ON BOTH ENGS, CHKED THE AIRSPD ON BOTH SIDES AND ANNOUNCED 90 KTS. I TOOK A QUICK GLANCE OUTSIDE AND THEN RECHKED THE ENG GAUGES. THE L WAS STILL SLIGHTLY LOW BUT WITHIN NORMAL LIMITS FOR AUTOTHROTTLE SETTING AT 1.32 EPR AND NOW ABOUT 82 PERCENT N1. INSTEAD OF JUST LIGHTLY MONITORING THE AUTOTHROTTLE AND GUARDING THE THROTTLES, I ATTEMPTED TO ACTIVELY 'TWEAK' THE L THROTTLE. THE THROTTLE MOVED VERY SLIGHTLY FORWARD AND HIT A MECHANICAL STOP APPROX 2 - 2 1/2 INCHES SHORT OF FULL TRAVEL. THE ACFT WAS NOW WELL INTO THE HIGH SPD REGIME OF THE TKOF AND ACCELERATION WAS NORMAL. GIVEN THOSE 2 FACTORS AND THE PREDEP BRIEFING THAT SHORT OF AN ENG FAILURE, FIRE, OR REVERSER UNLOCKED, WE WILL CONTINUE ANY TKOF FROM HIGH SPD UNLESS IT SEEMS THAT THE ACFT WILL NOT FLY, I ELECTED TO CONTINUE THE TKOF. OUT OF 3000 FT FOLLOWING THE AFTER TKOF CHKLIST, I BEGAN TO MORE ACTIVELY ATTEMPT TO IDENT THE CAUSE OF THE PROB. I CHKED THE REVERSE LEVEL DOWN, CHKED FOR ANY CIRCUIT BREAKERS POPPED, AND RETARDED THE THROTTLE SLIGHTLY AND ATTEMPTED TO PUSH IT FORWARD AGAIN. IT HIT THE SAME MECHANICAL STOP. INTERESTINGLY, DURING THE CLB AS THE CLB EPR INCREASED, SO DID THE ACTUAL INDICATED EPR REMAINING ABOUT 0.01 BELOW WHAT WAS CALLED FOR BY THE THRUST MGMNT COMPUTER. I TOLD THE FO I THOUGHT WE HAD A PROB. HE CHKED THE SAME THINGS I DID AND WE BEGAN TO DISCUSS OUR OPTIONS. HE EXPRESSED CONCERN ABOUT SINGLE ALT DRIFTDOWN OVER THE MOUNTAINS IF THE R ENG SHOULD QUIT ENRTE. I OFFERED THAT WE MIGHT USE A B737 TECHNIQUE OF HAVING DRIFTDOWN ALTERNATES FOR EACH SEGMENT OF THE FLT IF THE WX WAS ACCEPTABLE. WE CALLED DISPATCH AND BEGAN TO DISCUSS OUR PROB AND REQUESTED INFO ABOUT THE WX AT ACCEPTABLE ENRTE ALTERNATES. I BECAME CONCERNED, NOT ABOUT THE DRIFTDOWN AND LNDG, BUT ABOUT THE POSSIBILITY OF A SINGLE ENG GAR AT A HIGH ALT ARPT VERSUS A REDUCED PWR TKOF AT SEA LEVEL. WE ASKED DISPATCH TO CONNECT US WITH SYS ACFT MAINT CTL. WE DISCUSSED OUR PROB AND ASKED HIS OPINION ABOUT WHAT THRUST WE COULD EXPECT FROM THE L ENG GIVEN OUR SIT. HE STATED WHAT WE ALREADY EXPECTED, THAT THERE WAS NO WAY TO KNOW. HE RECOMMENDED THAT WE RETURN TO THE BAY AREA FOR AN ENG CHK. WE CONCURRED AND ADVISED DISPATCH THAT WITH THEIR BLESSING WE WOULD RETURN TO SFO IN ORDER TO HAVE BETTER PAX OPTIONS AND BETTER PARTS AVAILABILITY. WE LANDED NORMALLY AT SFO. SUBSEQUENT MAINT INSPECTION OF THE ENG REVEALED THAT IN WORKING ON THE REVERSER THE EVENING BEFORE, THE MECH HAD PULLED A CIRCUIT BREAKER IN THE COCKPIT AND SAFETIED IT WITH AN ORANGE COLLAR. A COLLARED BREAKER TO A PLT INDICATES THAT MAINT HAS TAKEN APPROPRIATE ACTION AND IS NOT A CONCERN, ESPECIALLY GIVEN A CLEAN MAINT RELEASE DOCUMENT, NO WARNING LIGHTS, AND NO EICAS WARNINGS, ADVISORIES, OR CAUTIONS. MY RECOMMENDED SOLUTION IS FIRST, ENGINEERING IDENT ALL CIRCUIT BREAKERS THAT WOULD POTENTIALLY POSE THIS KIND OF PROB -- THAT IS, PULLING THE CIRCUIT BREAKER COULD ADVERSELY AFFECT THE FLT BUT GIVE NO CREW WARNING. SECOND, MAINT SHOULD BE REQUIRED TO POST AN ORANGE OR RED 'NO FLY' PLACARD ON THE CTL WHEEL OR STICK ANY TIME ONE OF THESE CIRCUIT BREAKERS IS USED AS A SAFETY FOR THEIR WORK UNTIL THE CIRCUIT BREAKERS HAVE BEEN RESET.

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.