Narrative:

Primary invertor failed, auxiliary invertor picked up load and all was normal for approximately 5 min. Proper procedures for invertor fail were followed and we could not restore the primary invertor. Shortly thereafter the secondary invertor failed. We had loss of first officer flight instruments and partial loss of cockpit lighting. Shortly after, all 3 invertor fail caution lights illuminated on the caution panel with navigation flags on all associated flight instruments and partial loss of all cockpit lighting. The 3 invertors would cycle on and off periodically. We declared an emergency with ocean approach control, at this time our location was 16 NM east of pvd airport. We were vectored for the ILS runway 5R at pvd. The first officer was the PF and concentrated on maintaining aircraft attitude and navigation. I tried to determine cause, handled the radios, informed the passengers. By some aircraft of god we had enough gyro instrumentation to fly the airplane on radar vectors and the ILS to break out of the clouds and land at pvd without incident. The emergency equipment was present and we taxied to our station gate. The 50 passenger were off loaded to the terminal and accommodations were made for them by the gate agents. Remarks: since the invertors would come back on line intermittently this gave us enough gyro information to fly the aircraft. If we would have had continuous invertor failure with no standby attitude indicator, would we have been able to control the aircraft in night/IMC?

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Original NASA ASRS Text

Title: COMMUTER ACFT FLC EXPERIENCES SEVERE ELECTRICAL PROBLEMS WHILE IN IMC AT NIGHT.

Narrative: PRIMARY INVERTOR FAILED, AUX INVERTOR PICKED UP LOAD AND ALL WAS NORMAL FOR APPROX 5 MIN. PROPER PROCS FOR INVERTOR FAIL WERE FOLLOWED AND WE COULD NOT RESTORE THE PRIMARY INVERTOR. SHORTLY THEREAFTER THE SECONDARY INVERTOR FAILED. WE HAD LOSS OF FO FLT INSTS AND PARTIAL LOSS OF COCKPIT LIGHTING. SHORTLY AFTER, ALL 3 INVERTOR FAIL CAUTION LIGHTS ILLUMINATED ON THE CAUTION PANEL WITH NAV FLAGS ON ALL ASSOCIATED FLT INSTS AND PARTIAL LOSS OF ALL COCKPIT LIGHTING. THE 3 INVERTORS WOULD CYCLE ON AND OFF PERIODICALLY. WE DECLARED AN EMER WITH OCEAN APCH CTL, AT THIS TIME OUR LOCATION WAS 16 NM E OF PVD ARPT. WE WERE VECTORED FOR THE ILS RWY 5R AT PVD. THE FO WAS THE PF AND CONCENTRATED ON MAINTAINING ACFT ATTITUDE AND NAV. I TRIED TO DETERMINE CAUSE, HANDLED THE RADIOS, INFORMED THE PAXS. BY SOME ACFT OF GOD WE HAD ENOUGH GYRO INSTRUMENTATION TO FLY THE AIRPLANE ON RADAR VECTORS AND THE ILS TO BREAK OUT OF THE CLOUDS AND LAND AT PVD WITHOUT INCIDENT. THE EMER EQUIP WAS PRESENT AND WE TAXIED TO OUR STATION GATE. THE 50 PAX WERE OFF LOADED TO THE TERMINAL AND ACCOMMODATIONS WERE MADE FOR THEM BY THE GATE AGENTS. REMARKS: SINCE THE INVERTORS WOULD COME BACK ON LINE INTERMITTENTLY THIS GAVE US ENOUGH GYRO INFO TO FLY THE ACFT. IF WE WOULD HAVE HAD CONTINUOUS INVERTOR FAILURE WITH NO STANDBY ATTITUDE INDICATOR, WOULD WE HAVE BEEN ABLE TO CTL THE ACFT IN NIGHT/IMC?

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.