A B737-300 EXPERIENCED A STBY POWER SWITCH FAILURE CAUSING A BATTERY BUS FAILURE WITH NO ANNUNCIATOR LIGHTS INDICATING THE FAILURE.

Narrative

WE STARTED THE LAST LEG OF A 3 DAY TRIP IN ONT AND THE OFF-GOING PLTS BRIEFED US THAT THE #1 GEN WOULD SOMETIMES NOT TAKE THE ELECTRICAL LOAD AFTER ENG STARTS. THEY HAD THE ACFT FOR SEVERAL LEGS AND HAD MAINT LOOK AT THE ACFT THAT SAME DAY. MAINT DID CLEAR THE PROB AS THEY COULD NOT DUPLICATE THE SIT. WE FLEW THE ACFT UNEVENTFULLY AND THEN SUBSEQUENTLY TO OUR NEXT CITY WITH NO EVIDENCE OF GEN PROBLEMS. AFTER PUSHBACK AND ENG START FROM THE GATE; THE CAPT HAD A PROBLEM WITH THE #1 GEN AND IT WOULD NOT TAKE THE FULL ELECTRICAL LOAD AS EVIDENCED BY SEVERAL OVERHEAD LIGHTS REMAINING ON. HE HAD TURNED THE #1 ELECTRICAL LOAD TO THE APU GEN AT LEAST ONCE AND TRIED TO BUS UP WITH #1 GEN AGAIN AND THE #1 GEN DID TAKE THE LOAD NORMALLY. THE CAPT ASKED ME IF I FELT COMFORTABLE TAKING THE ACFT AND I SAID YES BECAUSE I THOUGHT IT WAS A TEMPERAMENTAL STICKY RELAY SOMEWHERE THAT WE MUST HAVE UNSTUCK. WE PROCEEDED TO THE RWY AND FROM A ROLLING TKOF; THE CAPT HAD SET TKOF THRUST SLIGHTLY ABOVE N1 MINIMUM SETTINGS. AFTER HE CALLED; 'SET TKOF THRUST;' I REACHED UP TO FINE TUNE THE N1 SETTINGS AND I NOTICED THAT WE HAD JUST LOST BOTH N1 AND EGT INDICATIONS FOR BOTH #1 AND #2 ENGS. WE HAD ALREADY ACCELERATED PAST 80 KTS AT THIS POINT AND I CALLED OUT THAT WE HAD JUST LOST N1 INDICATIONS. I REMEMBER THINKING THAT I KNEW WE WERE SAFE FOR TKOF SINCE I HAD SEEN MINIMUM INDICATIONS ON BOTH ENGS BEFORE WE LOST INDICATIONS. WE DID NOT REJECT AND WHEN THE CAPT CALLED FOR LNDG GEAR UP; I COULD NOT LIFT THE HANDLE PAST THE OFF POSITION. I PUT THE HANDLE BACK IN THE DOWN POSITION AND INFORMED THE CAPT. I REMEMBER SEEING THE RED NOSE GEAR LIGHT TEMPORARILY WHEN I HAD THE HANDLE NOT DOWN. WHEN THE HANDLE WAS BACK IN THE DOWN POSITION; THERE WERE NO GREEN LNDG GEAR POSITION INDICATOR LIGHTS; BUT WE HEARD THE RUSH OF AIR THAT SOUNDED FAMILIAR LIKE THE GEARS WERE DOWN. I CONTACTED DEP AND INFORMED THEM WE WOULD LIKE A VECTOR TO TROUBLESHOOT BECAUSE WE WERE EXPERIENCING AN ELECTRICAL PROBLEM AND WE COULD NOT RAISE OUR LNDG GEAR. THEY TOLD US TO LEVEL AT 3000 FT AND THEN ASKED US IF WE WOULD LIKE 5000 FT IN CASE WE NEEDED TO BE OVER CATALINA ISLAND. THE CAPT AND I AGREED TO ASK FOR 5000 FT SO WE CLBED FURTHER TO 5000 FT AND I ASKED FOR A BOX PATTERN OF VECTORS BECAUSE WE WOULD PROBABLY RETURN. THEY ASKED IF WE WANTED TO DECLARE AN EMER AND WE SAID; 'NOT AT THIS TIME.' THE CAPT NOTICED WE WEREN'T PRESSURIZING AND SOON DELEGATED THE FLYING TO ME AND THE RADIOS. HE TROUBLESHOT CIRCUIT BREAKERS; PULLED OUT THE QRH AND TALKED TO THE COMPANY OVER THE VHF AND ALSO TO THE FLT ATTENDANTS. I WAS ABLE TO ENGAGE THE AUTOPLT AND THE HDG AND ALT HOLD FUNCTIONED NORMALLY. THE OVERHEAD YELLOW INDICATOR LIGHTS WE HAD WERE MACH TRIM; SPD TRIM; AND AUTO SLAT. THE PA SYSTEM WAS NOT WORKING IN THE ACFT AND THE FLT ATTENDANTS TRIED TO COMMUNICATE TO PAX WITH THE BULLHORNS UNSUCCESSFULLY. THE CAPT WENT BACK TO THE CABIN AND VERIFIED ALL GEAR WERE DOWN WITH THE LNDG GEAR VIEWER IN THE CABIN AND IN THE COCKPIT. THE FLT ATTENDANTS MADE FACE TO FACE CONTACT WITH ALL THE PAX AND TOLD THEM WE WERE GOING TO RETURN FOR A NORMAL LNDG. ONCE THE GEAR WERE DETERMINED DOWN AND WE WERE AT A WT BELOW 114000 LBS WE ASKED FOR VECTORS BACK TO LAX. WHILE ON VECTORS BACK; WE NOTICED THE STANDBY ATTITUDE INDICATOR HAD STARTED TO TUMBLE. ON BASE LEG FOR RWY 25R VISUAL APCH ALL YELLOW LIGHTS DISAPPEARED AND THE N1 AND EGT INDICATIONS CAME BACK. THE STANDBY ATTITUDE GYRO WAS ERECTED AND STAYED ERECT. WE HAD REGAINED ALL THAT WE HAD INITIALLY LOST. WE LANDED UNEVENTFULLY ON RWY 25R. MAINT MET US AT THE GATE AND NOTICED A BAD STANDBY POWER SWITCH WHICH WAS HAIR TRIGGER TO THE TOUCH. WE THEN SWAPPED ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT 3 ATTEMPTS WERE REQUIRED TO GET THE #1 GEN ON LINE. HE DID NOT STATE IN HIS RPT THAT THE PREVIOUS CREW RPTED TO THEM WHEN HE AND THE CAPT ACCEPTED THE ACFT THAT THEY HAD MOMENTARY ANNUNCIATOR LIGHTS FOR THE MACH TRIM; SPD TRIM;AND AUTO SLAT FAILURES IN ADDITION TO THE GEN DIFFICULTY. THE RPTR DID NOT REMEMBER SEEING ANY ANNUNCIATOR LIGHTS ASSOCIATED WITH THE ELECTRICAL SYSTEM. THE MECHANIC THAT EXAMINED THE ACFT AFTER THE FACT SAID IN ADDITION TO THE SWITCH FAILING; THERE WAS ALSO A RELAY MALFUNCTION IN THE ELECTRICAL PANEL BEHIND THE FO. THE RPTR BELIEVES THE BIGGEST CULPRIT WAS THE STBY POWER SWITCH AND THAT THE WEAKNESS IN THE SWITCH MAY BE CAUSED DURING THE CAPT'S STBY POWER CHK WHEN MANY CAPTS SIMPLY SLAM THE SWITCH COVER CLOSED AT THE COMPLETION OF THE SYSTEM'S PREFLT. THE RPTR INDICATED THAT THE COVER CLOSING ACTION SHOULD PUT THE THEN COVERED SWITCH IN ITS NORMAL POSITION POWERING THE BATTERY BUS; BUT THAT SLAMMING THE COVER CLOSED VERSUS SELECTING THE SWITCH TO NORMAL FOLLOWED BY CLOSURE OF THE SWITCH GUARD CAN RESULT IN SWITCH DAMAGE. THE RPTR INDICATED THAT THE MAINT INVESTIGATION WAS BEING FOLLOWED BY THE FAA.