Narrative:

On the arrival into san francisco during descent (this is after two arrival changes); we got the right eec (electronic engine control) inoperative message on the EICAS and also lost the autothrottles. Had the first officer run the QRH and was unable to recover the autothrottles or engine controls. The right limiter was already MEL'd. We had several altitude changes non that were no stranded for the descent and at leave five airspeed changes. Finally got cleared for the FMS bridge visual; but then asked if we saw another aircraft at 10 o'clock. We did not then was told to level off immediately. Turned to a heading 180 degrees away and continued looking for this aircraft. We were also assigned a speed of 160 knots. Upon the level off I pushed the throttles up to match the aircraft level off; however the engines did not respond. The airspeed bled off to approximately 150 KIAS before the engines slowly spooled up (approximately a 10 second delay from the time I initially moved the throttles forward for increased thrust). We were all at flaps 20. Also; while all this was happening ATC kept giving us radio calls and turns and traffic to follow questions. By the time we were able to find several (3 aircraft in the location he was asking) he told us cleared for the visual. We were too high and out of position to make a safe landing. We went around and again the engines took forever. It took approximately 10 seconds to even start to spool up. Managed to come around and land uneventful second time. The major issues here being multiple ATC heading and altitude changes; no autothrottles; no engine control causing the engines to spool very very slowly and the constant distraction of trying to find an aircraft at night in the lights to follow.

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Original NASA ASRS Text

Title: B757 Captain reported executing a go-around after the approach became unstable following multiple arrival changes and a lagging throttle.

Narrative: On the arrival into San Francisco during descent (this is after two arrival changes); we got the right EEC (Electronic Engine Control) inoperative message on the EICAS and also lost the autothrottles. Had the FO run the QRH and was unable to recover the autothrottles or engine controls. The right limiter was already MEL'd. We had several altitude changes non that were no stranded for the descent and at leave five airspeed changes. Finally got cleared for the FMS Bridge Visual; but then asked if we saw another aircraft at 10 o'clock. We did not then was told to level off immediately. Turned to a heading 180 degrees away and continued looking for this aircraft. We were also assigned a speed of 160 knots. Upon the level off I pushed the throttles up to match the aircraft level off; however the engines did not respond. The airspeed bled off to approximately 150 KIAS before the engines slowly spooled up (approximately a 10 second delay from the time I initially moved the throttles forward for increased thrust). We were all at flaps 20. Also; while all this was happening ATC kept giving us radio calls and turns and traffic to follow questions. By the time we were able to find several (3 aircraft in the location he was asking) he told us cleared for the visual. We were too high and out of position to make a safe landing. We went around and again the engines took forever. It took approximately 10 seconds to even start to spool up. Managed to come around and land uneventful second time. The major issues here being multiple ATC heading and altitude changes; no autothrottles; no engine control causing the engines to spool very very slowly and the constant distraction of trying to find an aircraft at night in the lights to follow.

Data retrieved from NASA's ASRS site 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.