Narrative:

Began descent from FL430. Entered tops at 350 ft and turned on nacelle heat. At approximately FL300, essential bus and ties breakers blew. Lost all avionics and all three altimeters. Tried a reset and failed again. Second reset on left side returned power to pilot flying instruments. Continued on to destination. (About 4 mins. The lapsed time for the whole solution was approximately 3 mins.) aircraft is rvsm approved. Equipment affected, all navigation, communication, FMS, DME, 3 altimeters, mfd, ehsi, ivsi, and pressurization automatic function and xponders. Approximately 30 seconds prior to fail, we encountered two mod to severe thumps of wake turbulence. It is a possibility that the encounter caused a short to ground. We are going over the wires, etc, to isolate the problem. It would be a definite improvement to have an 'old steam gauge' as a standby altimeter. Callback conversation with reporter revealed the following information: the reporter said the loss of electrical power was traced to the two electrical splices at the bottom of the circuit breaker panels. These splices are the main feed to the circuit breaker busses and showed evidence of overheating with the plastic insulation flaking off. The reporter believes the two thumps of severe turbulence prior to the loss of power may have shorted one or both splices to ground, opening the bus tie breakers. These splices were the subject of a service bulletin on the lear 23, but did not apply to the lear 25. The reporter expresses concern about the loss of all three altimeters and suggests addition of the 'old steam gauge altimeter.'

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Original NASA ASRS Text

Title: A LEAR 25G IN DSCNT AT FL300 LOST ALL ELECTRICAL POWER TO ESSENTIAL BUSSES AND BUS TIE BREAKERS OPENED. LOST ALL AVIONICS AND THREE ALTIMETERS.

Narrative: BEGAN DSCNT FROM FL430. ENTERED TOPS AT 350 FT AND TURNED ON NACELLE HEAT. AT APPROX FL300, ESSENTIAL BUS AND TIES BREAKERS BLEW. LOST ALL AVIONICS AND ALL THREE ALTIMETERS. TRIED A RESET AND FAILED AGAIN. SECOND RESET ON LEFT SIDE RETURNED POWER TO PLT FLYING INSTRUMENTS. CONTINUED ON TO DEST. (ABOUT 4 MINS. THE LAPSED TIME FOR THE WHOLE SOLUTION WAS APPROX 3 MINS.) ACFT IS RVSM APPROVED. EQUIP AFFECTED, ALL NAV, COM, FMS, DME, 3 ALTIMETERS, MFD, EHSI, IVSI, AND PRESSURIZATION AUTO FUNCTION AND XPONDERS. APPROX 30 SECONDS PRIOR TO FAIL, WE ENCOUNTERED TWO MOD TO SEVERE THUMPS OF WAKE TURB. IT IS A POSSIBILITY THAT THE ENCOUNTER CAUSED A SHORT TO GND. WE ARE GOING OVER THE WIRES, ETC, TO ISOLATE THE PROB. IT WOULD BE A DEFINITE IMPROVEMENT TO HAVE AN 'OLD STEAM GAUGE' AS A STANDBY ALTIMETER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THE LOSS OF ELECTRICAL POWER WAS TRACED TO THE TWO ELECTRICAL SPLICES AT THE BOTTOM OF THE CIRCUIT BREAKER PANELS. THESE SPLICES ARE THE MAIN FEED TO THE CIRCUIT BREAKER BUSSES AND SHOWED EVIDENCE OF OVERHEATING WITH THE PLASTIC INSULATION FLAKING OFF. THE RPTR BELIEVES THE TWO THUMPS OF SEVERE TURB PRIOR TO THE LOSS OF POWER MAY HAVE SHORTED ONE OR BOTH SPLICES TO GND, OPENING THE BUS TIE BREAKERS. THESE SPLICES WERE THE SUBJECT OF A SERVICE BULLETIN ON THE LEAR 23, BUT DID NOT APPLY TO THE LEAR 25. THE RPTR EXPRESSES CONCERN ABOUT THE LOSS OF ALL THREE ALTIMETERS AND SUGGESTS ADDITION OF THE 'OLD STEAM GAUGE ALTIMETER.'

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.