LR35 SUFFERS COMPLETE LOSS OF NAVAID AND COM RADIOS WHILE DSNDING FROM FL370. FLT CREW FOLLOWS LOST COM PROCS TO SAFE ARR AT DEST ARPT USING LIGHT SIGNALS FOR LNDG CLRNC.

Date: 2006-05 · Aircraft: Learjet 35

Anomalies: aircraft-equipment-problem-critical

Synopsis

LR35 SUFFERS COMPLETE LOSS OF NAVAID AND COM RADIOS WHILE DSNDING FROM FL370. FLT CREW FOLLOWS LOST COM PROCS TO SAFE ARR AT DEST ARPT USING LIGHT SIGNALS FOR LNDG CLRNC.

Narrative

JUST PRIOR TO INITIATING DSCNT FROM FL370; WE EXPERIENCED COMPLETE LOSS OF OUR EFIS SYS; COM AND NAV RADIOS; XPONDER; AND VARIOUS OTHER ELECTRICAL EQUIP. WE WERE IN VMC WITH VARIABLE BROKEN TO OVCST CLOUDS BELOW; WITH WIDELY SCATTERED AREAS WHERE WE COULD SEE THE GND. CURRENT WX AT ROG WAS RPTED AS VFR WITH A BROKEN LAYER OF CLOUDS AROUND 4000 FT. WE WERE ABOUT 15 MINS FROM OUR DEST WITH ABOUT 1 HR 30 MINS OF FUEL REMAINING. AFTER OUR INITIAL ATTEMPTS TO REGAIN PWR TO OUR COM AND NAV RADIOS FAILED; WE AGREED TO BEGIN OUR DSCNT TOWARDS ROG. AT THIS POINT WE WERE FLYING THE AIRPLANE USING ONLY OUR STANDBY ATTITUDE INDICATOR; COPLT'S VSI; STANDBY ALTIMETER; AND MAGNETIC COMPASS. DURING THE DSCNT WE NOTICED THAT THE #1 EADI CIRCUIT BREAKER HAD POPPED. ONCE ON THE GND; WE DISCOVERED THAT IT WAS ACTUALLY THE 'ESSENTIAL A' BUS BREAKER (PLT'S SIDE) THAT HAD POPPED. THERE IS A CHKLIST PROC FOR DC BUS FAILURE THAT WE COULD HAVE COMPLETED; POSSIBLY RESTORING SOME PWR TO THE R OR L 'ESSENTIAL A' BUS; HAD WE RECOGNIZED WHAT CIRCUIT BREAKER HAD POPPED AND ELECTED TO RESET BREAKERS. LABELING AND POS OF THE BREAKERS ARE SUCH THAT THE LABEL FOR THE BREAKER IS BELOW THE BREAKER AND POSITIONED LOW BEHIND THE PLT'S L KNEE (OR COPLT'S R KNEE). WE MISTAKENLY READ THE LABEL ABOVE THE BREAKER. DURING DSCNT; WE SPONTANEOUSLY REGAINED LOST ELECTRICAL PWR TO EFIS; COM AND NAV SYS FOR ABOUT 30 SECONDS. THE FO CALLED ZKC AND RPTED OUR ELECTRICAL PROB. BEFORE HE WAS ABLE TO DECLARE AN EMER; WE LOST COM AGAIN. AFTER OUR SECOND PWR LOSS; THE FO NOTED WHAT HE THOUGHT WAS A POPPED #2 EHSI CIRCUIT BREAKER. AGAIN; WE MISREAD THIS AND HAD ACTUALLY POPPED THE R 'ESSENTIAL A' BUS BREAKER. CONTINUING TO TROUBLESHOOT; I ASKED THE FO TO TRY HIS BACKUP RADIO SWITCH LOCATED ON THE AFT BOTTOM ROW OF THE CIRCUIT BREAKER PANEL. HE DID AND WE REGAINED USE OF OUR VOR; DME; AND ADF RECEIVERS. I DON'T RECALL FOR SURE BUT WE MAY HAVE HAD ADF THE WHOLE TIME. DURING DSCNT WE DISCUSSED AND DECIDED AGAINST RESETTING CIRCUIT BREAKERS. WE DISCUSSED USING CELL PHONES TO CONTACT FSS BUT BY THIS TIME WE WERE WITHIN APPROX 40 NM OF ROG AND WERE REASONABLY CONFIDENT THAT WE WOULD BE ABLE TO NAV CLR OF CLOUDS USING PILOTAGE TO THE ARPT. OUR FOCUS HAD SHIFTED TO WHAT SYS WERE AFFECTED THAT WE WOULD NEED FOR LNDG AND CONSIDERED AND/OR TESTED THE AVAILABILITY OF FLAPS; SPOILER; LNDG GEAR AND ANTI-SKID SYS. DURING DSCNT; CLOUDS HAD FORCED US TO MANEUVER S OF THE INITIAL MAGNETIC HDG THAT WE WERE MAINTAINING TO ROG. OUR FIRST POSITIVE IDENT OF ANY LANDMARK WAS ON TOP OF XNA WHICH WAS IN THE CLR AT THAT TIME. WE CONTINUED OUR DSCNT NBOUND AND E OF XNA THROUGH A LARGE HOLE IN THE CLOUDS. WE DISCUSSED LNDG AT XNA BUT AGREED TO CONTINUE ON TO ROG KNOWING XNA WAS A GOOD OPTION IF WE HAD ANY TROUBLE FINDING ROG. WE DSNDED BELOW THE CLOUD DECK; IDENTED VBT AND ROG SHORTLY THEREAFTER. SINCE OUR PROB WAS MORE THAN JUST COM FAILURE WE ENTERED THE PATTERN ON A WIDE R BASE FOR RWY 20; WHICH WE WERE MOST CONVENIENTLY SET UP FOR. MY ASSUMPTION WAS THAT ZKC WOULD ALERT RAZORBACK APCH AND ROGERS TWR TO OUR SITUATION. ON FINAL APCH TO LAND; WE RECEIVED AND ACKNOWLEDGED LIGHT GUN SIGNALS FROM THE TWR. DESPITE WHAT THE CHKLISTS SAY; WE ARE STRONGLY ENCOURAGED IN TRAINING TO NOT RESET POPPED BREAKERS UNLESS ABSOLUTELY NECESSARY. THIS TRAINING AFFECTS OUR RESPONSE TO ELECTRICAL PROBS. IF WE HAD PROPERLY IDENTED THE CIRCUIT BREAKERS THAT POPPED WE WOULD HAVE RUN THE APPROPRIATE CHKLIST. HOWEVER; GIVEN OUR SITUATION AT THE TIME AND IN LIGHT OF OUR TRAINING; WE WOULD HAVE LIKELY ELECTED TO NOT RESET THE CIRCUIT BREAKERS. OUR OVERALL SITUATIONAL AWARENESS WOULD HAVE IMPROVED BUT OUR DECISIONS AND OUTCOMES WOULD HAVE REMAINED THE SAME.

Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.