Narrative:

Aircraft had a right generator MEL that required the APU to run for the entire flight. In cruise we received an APU fuel valve message on the EICAS. The QRH directed that the APU to be shutoff and not restarted. If we shut down the APU then we are put into an emergency situation since we would be operating on a single generator. The APU was running normally at 100% RPM and steady egt (exhaust gas temperature). We elected to continue while monitoring the APU since it was providing needed electrical power. We were monitoring possible divert fields as we went in case the APU did actually fail. The APU ran steady until on the decent through FL200 when it failed. We [advised ATC] due to single generator operation and landed uneventfully.

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Original NASA ASRS Text

Title: On a B757-200 a failed APU coupled with a deferred right engine generator caused to operate in a single generator mode.

Narrative: Aircraft had a Right Generator MEL that required the APU to run for the entire flight. In cruise we received an APU FUEL VALVE message on the EICAS. The QRH directed that the APU to be shutoff and not restarted. If we shut down the APU then we are put into an emergency situation since we would be operating on a single generator. The APU was running normally at 100% RPM and steady EGT (Exhaust Gas Temperature). We elected to continue while monitoring the APU since it was providing needed electrical power. We were monitoring possible divert fields as we went in case the APU did actually fail. The APU ran steady until on the decent through FL200 when it failed. We [advised ATC] due to single generator operation and landed uneventfully.

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.