Narrative:

At FL390, approximately 10-15 mi into the flight, in cruise confign en route to hou, we experienced a loss of communications, immediately followed by a loss of navigation equipment and gyroscopes at pilot side. Initial squawk was 7600, followed by a squawk of 7700 once the navaids were lost. Realizing we would not be able to navigation to our destination, per FARS for loss of communications, we proceeded to commence a 180 degree reversal and return to our maintenance facility in mor, under VFR conditions. As we began our turn and descent, the #2 engine flamed out. The cabin pressurization began to climb and the flight nurse in the back (no patients) began to become hysterical and was quite a distraction. Attempts were made to calm her down, however, unsuccessfully. As we passed through FL280, we attempted a relight of the #2 engine and it was successful. As we continued our descent and after liftoff of the #2 engine, we cycled the generators and were able to restore dc power with the #2 generator, however, we then lost our ADF and transponder, yet it appeared we were able to restore our communications and navs. We began to broadcast our intentions in the blind to knoxville approach and advised them we would be landing at mor and requested emergency assistance. We landed uneventfully and safely at mor. I believe the problem was due to loss of dc power. The aircraft we were flying was a 30 yr old learjet 23 series. This model has electric standby and main boost pumps. Due to power loss of dc I assume the engine experienced loss of fuel pressure and was unable to suction feed at FL390. Because once we were down to the lower altitudes we were able to restart. It's possible the air ambulance equipment somehow caused an electrical surge causing dc generator relays to open from an overload and they failed to close afterwards. Once the circuitry cooled down and we attempted cycling the switches, the right generator came on line. Afterwards maintenance discovered that the right generator was out of parallel with the left side, and carried most of the total load. Supplemental information from acn 293146: our maintenance chief informed us later the engine flameout was caused by the right standby bump circuit breakers in rear compartment blowing, resulting in low fuel pressure to the #2 engine. The loss of navs and communications was a result of an overvoltage of the #1 generator. This, coupled with an incorrect paralleling of the generators, caused a disruption of dc power which resulted in the loss of associated equipment.

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Original NASA ASRS Text

Title: AN EMER SIT MAJOR ELECTRICAL FAILURE.

Narrative: AT FL390, APPROX 10-15 MI INTO THE FLT, IN CRUISE CONFIGN ENRTE TO HOU, WE EXPERIENCED A LOSS OF COMS, IMMEDIATELY FOLLOWED BY A LOSS OF NAV EQUIP AND GYROSCOPES AT PLT SIDE. INITIAL SQUAWK WAS 7600, FOLLOWED BY A SQUAWK OF 7700 ONCE THE NAVAIDS WERE LOST. REALIZING WE WOULD NOT BE ABLE TO NAV TO OUR DEST, PER FARS FOR LOSS OF COMS, WE PROCEEDED TO COMMENCE A 180 DEG REVERSAL AND RETURN TO OUR MAINT FACILITY IN MOR, UNDER VFR CONDITIONS. AS WE BEGAN OUR TURN AND DSCNT, THE #2 ENG FLAMED OUT. THE CABIN PRESSURIZATION BEGAN TO CLB AND THE FLT NURSE IN THE BACK (NO PATIENTS) BEGAN TO BECOME HYSTERICAL AND WAS QUITE A DISTR. ATTEMPTS WERE MADE TO CALM HER DOWN, HOWEVER, UNSUCCESSFULLY. AS WE PASSED THROUGH FL280, WE ATTEMPTED A RELIGHT OF THE #2 ENG AND IT WAS SUCCESSFUL. AS WE CONTINUED OUR DSCNT AND AFTER LIFTOFF OF THE #2 ENG, WE CYCLED THE GENERATORS AND WERE ABLE TO RESTORE DC PWR WITH THE #2 GENERATOR, HOWEVER, WE THEN LOST OUR ADF AND XPONDER, YET IT APPEARED WE WERE ABLE TO RESTORE OUR COMS AND NAVS. WE BEGAN TO BROADCAST OUR INTENTIONS IN THE BLIND TO KNOXVILLE APCH AND ADVISED THEM WE WOULD BE LNDG AT MOR AND REQUESTED EMER ASSISTANCE. WE LANDED UNEVENTFULLY AND SAFELY AT MOR. I BELIEVE THE PROB WAS DUE TO LOSS OF DC PWR. THE ACFT WE WERE FLYING WAS A 30 YR OLD LEARJET 23 SERIES. THIS MODEL HAS ELECTRIC STANDBY AND MAIN BOOST PUMPS. DUE TO PWR LOSS OF DC I ASSUME THE ENG EXPERIENCED LOSS OF FUEL PRESSURE AND WAS UNABLE TO SUCTION FEED AT FL390. BECAUSE ONCE WE WERE DOWN TO THE LOWER ALTS WE WERE ABLE TO RESTART. IT'S POSSIBLE THE AIR AMBULANCE EQUIP SOMEHOW CAUSED AN ELECTRICAL SURGE CAUSING DC GENERATOR RELAYS TO OPEN FROM AN OVERLOAD AND THEY FAILED TO CLOSE AFTERWARDS. ONCE THE CIRCUITRY COOLED DOWN AND WE ATTEMPTED CYCLING THE SWITCHES, THE R GENERATOR CAME ON LINE. AFTERWARDS MAINT DISCOVERED THAT THE R GENERATOR WAS OUT OF PARALLEL WITH THE L SIDE, AND CARRIED MOST OF THE TOTAL LOAD. SUPPLEMENTAL INFO FROM ACN 293146: OUR MAINT CHIEF INFORMED US LATER THE ENG FLAMEOUT WAS CAUSED BY THE R STANDBY BUMP CIRCUIT BREAKERS IN REAR COMPARTMENT BLOWING, RESULTING IN LOW FUEL PRESSURE TO THE #2 ENG. THE LOSS OF NAVS AND COMS WAS A RESULT OF AN OVERVOLTAGE OF THE #1 GENERATOR. THIS, COUPLED WITH AN INCORRECT PARALLELING OF THE GENERATORS, CAUSED A DISRUPTION OF DC PWR WHICH RESULTED IN THE LOSS OF ASSOCIATED EQUIP.

Data retrieved from NASA's ASRS site as of July 2007 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.