Narrative:

While established on the instrument approach in IMC; aircraft instruments failed. The aircraft entered unusual attitudes and the altitude and heading parameters of the approach were violated. After the aircraft was recovered; as PIC; I made a decision to get re-established on the inbound course and altitude using auxiliary backup equipment and land the aircraft. The missed approach was not executed because of loss of communication and navigation equipment. The ability to xfer fuel from auxiliary tanks for flight to VFR conditions was also lost. The transponder also was assumed to have failed and known IFR traffic in the immediate area could have been compromised. An emergency was not declared because of loss of communication equipment. A non-certified backup garmin 496 GPS was switched to battery backup and used to get re-established. All unnecessary electrical equipment was shut off and power was conserved for the gear and flaps. The certified garmin 430 GPS was subsequently determined to be unreliable and shut down. The radio was failing; the turn coordinator failed; fuel flow analyzer and engine gas temperature; cylinder head temperature gauges all failed; engine temperature; fuel level gauges; ammeter; engine temperature; storm scope; transponder; VOR; and NDB also failed. The aircraft is in maintenance. It is believed that the problem was a result of low voltage and a failure of the aircraft alternator. The pilot failed to recognize the voltage drop in time to prevent the emergency. The instruments did not obviously fail until the gear was extended. They simply gave incorrect information or had a dangerous lag time of several seconds. The unusual attitudes resulted from a disagreement between flight instruments and the pilot overcorrecting to failed instruments. The HSI; the garmin 430; and the garmin 496 headings were different. The compass was off due to wind correction angle. The electric turn coordinator was indicating straight and level flight. The attitude indicator indicated a steep right turn. The pilot overcorrected the heading and inadvertently got into a steep bank to the left. Altitude was lost and subsequently overcorrected. Straight and level flight was re-established using the attitude indicator and altimeter and compass. As failed instruments were idented and vacuum driven instruments were effectively utilized; the approach was completed.

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Original NASA ASRS Text

Title: A BE33'S ALTERNATOR FAILED THEN THE BATTERY DRAINED. AFTER ALL INSTRUMENTS FAILED THE PILOT ENTERED UNCONTROLLED FLT ON IMC APCH RECOVERING WITH VACUUM INSTRUMENTS.

Narrative: WHILE ESTABLISHED ON THE INST APCH IN IMC; ACFT INSTS FAILED. THE ACFT ENTERED UNUSUAL ATTITUDES AND THE ALT AND HDG PARAMETERS OF THE APCH WERE VIOLATED. AFTER THE ACFT WAS RECOVERED; AS PIC; I MADE A DECISION TO GET RE-ESTABLISHED ON THE INBOUND COURSE AND ALT USING AUX BACKUP EQUIP AND LAND THE ACFT. THE MISSED APCH WAS NOT EXECUTED BECAUSE OF LOSS OF COM AND NAV EQUIP. THE ABILITY TO XFER FUEL FROM AUX TANKS FOR FLT TO VFR CONDITIONS WAS ALSO LOST. THE XPONDER ALSO WAS ASSUMED TO HAVE FAILED AND KNOWN IFR TFC IN THE IMMEDIATE AREA COULD HAVE BEEN COMPROMISED. AN EMER WAS NOT DECLARED BECAUSE OF LOSS OF COM EQUIP. A NON-CERTIFIED BACKUP GARMIN 496 GPS WAS SWITCHED TO BATTERY BACKUP AND USED TO GET RE-ESTABLISHED. ALL UNNECESSARY ELECTRICAL EQUIP WAS SHUT OFF AND PWR WAS CONSERVED FOR THE GEAR AND FLAPS. THE CERTIFIED GARMIN 430 GPS WAS SUBSEQUENTLY DETERMINED TO BE UNRELIABLE AND SHUT DOWN. THE RADIO WAS FAILING; THE TURN COORDINATOR FAILED; FUEL FLOW ANALYZER AND ENG GAS TEMP; CYLINDER HEAD TEMP GAUGES ALL FAILED; ENG TEMP; FUEL LEVEL GAUGES; AMMETER; ENG TEMP; STORM SCOPE; XPONDER; VOR; AND NDB ALSO FAILED. THE ACFT IS IN MAINT. IT IS BELIEVED THAT THE PROB WAS A RESULT OF LOW VOLTAGE AND A FAILURE OF THE ACFT ALTERNATOR. THE PLT FAILED TO RECOGNIZE THE VOLTAGE DROP IN TIME TO PREVENT THE EMER. THE INSTS DID NOT OBVIOUSLY FAIL UNTIL THE GEAR WAS EXTENDED. THEY SIMPLY GAVE INCORRECT INFO OR HAD A DANGEROUS LAG TIME OF SEVERAL SECONDS. THE UNUSUAL ATTITUDES RESULTED FROM A DISAGREEMENT BTWN FLT INSTS AND THE PLT OVERCORRECTING TO FAILED INSTS. THE HSI; THE GARMIN 430; AND THE GARMIN 496 HDGS WERE DIFFERENT. THE COMPASS WAS OFF DUE TO WIND CORRECTION ANGLE. THE ELECTRIC TURN COORDINATOR WAS INDICATING STRAIGHT AND LEVEL FLT. THE ATTITUDE INDICATOR INDICATED A STEEP R TURN. THE PLT OVERCORRECTED THE HDG AND INADVERTENTLY GOT INTO A STEEP BANK TO THE L. ALT WAS LOST AND SUBSEQUENTLY OVERCORRECTED. STRAIGHT AND LEVEL FLT WAS RE-ESTABLISHED USING THE ATTITUDE INDICATOR AND ALTIMETER AND COMPASS. AS FAILED INSTS WERE IDENTED AND VACUUM DRIVEN INSTS WERE EFFECTIVELY UTILIZED; THE APCH WAS COMPLETED.

Data retrieved from NASA's ASRS site as of May 2009 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.