Narrative:

I departed ZZZ airport in fog just before XA00 am. I was the sole occupant and single pilot of a C90GT; on my way to pick up passenger in ZZZ1 for a part 91 flight. I was on an IFR flight plan and had completed my preflight checks and departed as instructed on runway heading 240 degrees up to 2000 ft MSL. I engaged the autoplt; and tower told me to fly heading 270 degrees and switched me to departure. I was on the 270 degree heading leveling at 2000 ft when departure instructed a right turn to heading 330 degrees and climb to 3000 ft MSL. I input the heading change as I was listening; and the aircraft started to turn. I may have input the new altitude; but at that moment my eadi and ehsi both went blank with failure annunciations on the screens; and I received 2 warning notices on the annunciator panel with the master warning flasher. I extinguished the flasher and acknowledged the inverter failure and autoplt failure annunciations. To the best of my recollection; events unfolded as follows: I told ATC I had a primary flight display failure and that I was unable to comply with previous instructions while I dealt with the problem; asking him to stand by. I either declared an emergency at this time or in a second radio transmission. I checked to see if circuit breakers were popped and if my RMI was providing heading information. I switched to the #2 inverter and extinguished the related master warning flasher. Both displays illuminated and while my ehsi had returned; I believed my eadi was indicating erroneously. I didn't trust my primary eadi; so I felt it was unsafe to activate the autoplt. I crosschecked the eadi with the r-seat attitude indicator; found that they didn't agree; and concluded that the right turn had increased and that the aircraft was in a descent. I felt disoriented and knew that safety of flight was an immediate concern. I focused on the r-seat instruments as I told ATC I was struggling to control the aircraft. Airspeed approached the barber pole limitation so I reduced power; rolled wings left using the r-seat attitude indicator to level my wings and applied back pressure to the yoke to stop the descent indicated on my primary altimeter. The lowest altitude I observed was 800 ft MSL.

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Original NASA ASRS Text

Title: A KING AIR C90'S PRIMARY INVERTER FAILED AFTER TKOF CAUSING EHSI AND EADI FAILURES. THE PILOT RECOVERED FROM UNUSUAL ATTITUDES AFTER ANOTHER INVERTER ACTIVATED.

Narrative: I DEPARTED ZZZ ARPT IN FOG JUST BEFORE XA00 AM. I WAS THE SOLE OCCUPANT AND SINGLE PLT OF A C90GT; ON MY WAY TO PICK UP PAX IN ZZZ1 FOR A PART 91 FLT. I WAS ON AN IFR FLT PLAN AND HAD COMPLETED MY PREFLT CHKS AND DEPARTED AS INSTRUCTED ON RWY HDG 240 DEGS UP TO 2000 FT MSL. I ENGAGED THE AUTOPLT; AND TWR TOLD ME TO FLY HDG 270 DEGS AND SWITCHED ME TO DEP. I WAS ON THE 270 DEG HDG LEVELING AT 2000 FT WHEN DEP INSTRUCTED A R TURN TO HDG 330 DEGS AND CLB TO 3000 FT MSL. I INPUT THE HDG CHANGE AS I WAS LISTENING; AND THE ACFT STARTED TO TURN. I MAY HAVE INPUT THE NEW ALT; BUT AT THAT MOMENT MY EADI AND EHSI BOTH WENT BLANK WITH FAILURE ANNUNCIATIONS ON THE SCREENS; AND I RECEIVED 2 WARNING NOTICES ON THE ANNUNCIATOR PANEL WITH THE MASTER WARNING FLASHER. I EXTINGUISHED THE FLASHER AND ACKNOWLEDGED THE INVERTER FAILURE AND AUTOPLT FAILURE ANNUNCIATIONS. TO THE BEST OF MY RECOLLECTION; EVENTS UNFOLDED AS FOLLOWS: I TOLD ATC I HAD A PRIMARY FLT DISPLAY FAILURE AND THAT I WAS UNABLE TO COMPLY WITH PREVIOUS INSTRUCTIONS WHILE I DEALT WITH THE PROB; ASKING HIM TO STAND BY. I EITHER DECLARED AN EMER AT THIS TIME OR IN A SECOND RADIO XMISSION. I CHKED TO SEE IF CIRCUIT BREAKERS WERE POPPED AND IF MY RMI WAS PROVIDING HDG INFO. I SWITCHED TO THE #2 INVERTER AND EXTINGUISHED THE RELATED MASTER WARNING FLASHER. BOTH DISPLAYS ILLUMINATED AND WHILE MY EHSI HAD RETURNED; I BELIEVED MY EADI WAS INDICATING ERRONEOUSLY. I DIDN'T TRUST MY PRIMARY EADI; SO I FELT IT WAS UNSAFE TO ACTIVATE THE AUTOPLT. I XCHKED THE EADI WITH THE R-SEAT ATTITUDE INDICATOR; FOUND THAT THEY DIDN'T AGREE; AND CONCLUDED THAT THE R TURN HAD INCREASED AND THAT THE ACFT WAS IN A DSCNT. I FELT DISORIENTED AND KNEW THAT SAFETY OF FLT WAS AN IMMEDIATE CONCERN. I FOCUSED ON THE R-SEAT INSTS AS I TOLD ATC I WAS STRUGGLING TO CTL THE ACFT. AIRSPD APCHED THE BARBER POLE LIMITATION SO I REDUCED PWR; ROLLED WINGS L USING THE R-SEAT ATTITUDE INDICATOR TO LEVEL MY WINGS AND APPLIED BACK PRESSURE TO THE YOKE TO STOP THE DSCNT INDICATED ON MY PRIMARY ALTIMETER. THE LOWEST ALT I OBSERVED WAS 800 FT MSL.

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.