AN ACR MLG LOST ALL OF ITS PRIMARY FLT INSTS.

Narrative

IN SUM: BOTH THE CAPT AND FO OF AN ACR B737-300 RPTED THIS INCIDENT. EACH RPTR TOLD ESSENTIALLY THE SAME STORY. THE ACFT DEPARTED INTO A LOW OVCST; TURNING TO THE E TOWARDS HIGH GND. ABOUT 10 MINS INTO THE FLT; THE #1 FUEL VALVE LIGHT STARTED FLICKERING; THEN CAME ON STEADY. THEN ALL PRIMARY FLT INSTS WENT BLANK ON THE GLASS COCKPIT. THERE WERE NO WARNING LIGHTS ON THE OVERHEAD PANEL AND THE PRESSURIZATION STAYED NORMAL. THE CAPT STARTED THE APU WHILE THE FO CHKED THAT ALL CIRCUIT BREAKERS WERE IN PLACE. THE CAPT PUT APU PWR ONTO THE L GENERATOR BUS AND PASSED CTL TO THE FO. THE CAPT HAD BEEN FLYING USING THE STANDBY INSTS. THE CAPT ASKED FOR AN 'IMMEDIATE RETURN TO SEA;' DESCRIBING THE SIT AS A 'COMPLETE ELECTRICAL FAILURE.' THE CAPT'S INSTS WERE INOP; WHILE THE FO'S INSTS AND THE STANDBY INSTS WERE OPERATING. THE YAW DAMPER; MACH TRIM AND SPD TRIM WERE INOP. THE DME AND XPONDER WERE INOP FOR A TIME; THEN BECAME OPERATIVE WHEN SWITCHED TO THE R SIDE. THE FO TRIED TO USE THE AUTOPLT UNTIL THE ALT STARTED TO DRIFT. THE APCH WAS COMPLETED HAND FLYING THE ACFT. THE LNDG WAS MADE TO THE LONGEST RWY; INTO THE WIND AND WAS UNEVENTFUL. AFTER THE CREW LEFT THE COCKPIT; MAINT FOUND THAT THE #1 AIR- CONDITIONING BUS CIRCUIT BREAKER HAD 'POPPED.' CALLBACK CONVERSATION WITH RPTR ACN 327403 REVEALED THE FOLLOWING INFO: THE RPTR HAS NOT YET GOTTEN THE FINAL REPLY FROM HIS ACR; BUT HE HAS HEARD THAT MAINT FOUND A CIRCUIT BREAKER THAT FAILED. IT BROKE THE CIRCUIT; BUT DID NOT SHOW 'POPPED' IN THE COCKPIT. THE RPTR HAS NOT SEEN THIS INST FAILURE BEFORE; 'ONLY IN THE SIMULATOR.' MAINT CHANGED THE FUEL VALVE; CIRCUIT BREAKER; AND POS XMITTER TO SOLVE THE FUEL LIGHT PROB. THE RPTR BELIEVES THAT THESE PROBS WERE ENTIRELY COINCIDENTAL AND NOT LINKED IN ANY WAY. CALLBACK CONVERSATION WITH RPTR ACN 326806 REVEALED THE FOLLOWING INFO: THIS RPTR HAS NOTHING MORE TO OFFER THAN HIS CAPT. HE; TOO; BELIEVES; THAT THIS WAS A ONE TIME ABERRATION. HE DID NOT GET OUT OF HIS SEAT TO CHK THE CIRCUIT BREAKER PANELS; BUT HE DID LOOSEN HIS SEAT BELT SO THAT HE COULD TOUCH EVERY ONE TO SEE THAT IT WAS NOT 'POPPED.'