Narrative:

Climbing to cruising altitude at dusk (climbing back into the sunset; but IMC in clouds); the aircraft was passing through FL230 on the way to FL260; the aircraft suffered a dual main bus breaker failure. The plane was climbing through layers of IMC clouds; light ice; accordingly the electrical anti-ice/de-ice systems were on including windshield heat (always on above FL180); pitot heat (always on for all flights); stall warning heat; prop heat; and cabin electrical auxiliary heat for windshield defog. Systems on for much of the climb; but at some point either transient voltage greater than the dual 80 amp breakers could handle; or resistance on one breaker increased. Regardless of the cause; the result was a failure of numerous systems tied to the main bus including: pilot's pfd/mfd (garmin G500); copilot sandel ehsi failed; copilot electric attitude indicator (ai) probably spooled down (unclear and didn't check); all cabin illumination; wing to header tank fuel pumps; header tank to PT6A electrical boost pump; annunciator panel; all engine instruments (torque/temperature; fuel flow/pressure/quantity; oil temperature/pressure; vacuum pressure); all of the above mentioned anti/de-ice electrical systems; de-ice boot activation switch; p3 heat; and a bunch more that is not relevant to the situation. Dual GPS nav/comms (avidyne ifd 540/440 with large map displays); radar; xm weather; traffic; transponder; and generator/battery volts/amp indicator continued to work worked. (Since the nav/comm and transponders were working; ATC communication was maintained and until I noted the issue to them; they were unaware of any problems.) the autopilot control head was illuminated; but without the ahrs from the G500; it wasn't functional.the pilot's backup instruments (airspeed; vacuum driven ai; and altimeter) were all functioning. Using the backup instruments; I maintained positive control of the aircraft while splitting my time to troubleshoot the problem. I advised ATC that I might need vectors to the nearest best weather; however; I did not want to immediately descend back into the much worse weather lower down (rain/snow/winds; low visibility). There was some wandering of heading and altitude during this period as I was forced to split focus between the instruments and checking breakers/etc using a flashlight. Shortly after the failure; I emerged out of the tops of the clouds in that area and in VMC conditions; and had no immediate icing concerns. With the loss of the wing fuel pumps to the header tank; I knew that although siphoning would continue to pull fuel to the header tank; it would be at a slower rate and fuel to the engine might eventually become an issue.the breakers would not initially reset since the electrical systems were all still on. However; after load-shedding some of the icing equipment via their individual circuit breakers --since the 'dead' control panel contains lighted push buttons (green dot light when on) without physical indication of whether they are on or off-- and waiting for a brief period; I was able to restore power to both main bus breakers. I was able to maintain an amp load below 70 amps for all electrical use (below the level of a single main breaker) in the plane with pitot and windshield heat on. I was actually enroute to the maintenance facility (for annual inspection); and much better weather was ahead at my destination than what was below. I elected to continue the trip and there were no further issues.in retrospect; this failure would not have happened had I not engaged the 'aux heat' which is an electric heater that warms the air coming out of the vent defog blower fan. That heater draws considerable amperage and I rarely have it on in active icing conditions. Generally that heater is on in high altitude cruise when it is too cold for icing; so only the pitot and windshield heaters are on when that is switched on. In those conditions the load is well below the 160 amp limit. It wasthe confluence of all the electrical systems engaged together with what may perhaps have been degraded breakers. I will recommend that the poh advise of high electrical loads in icing conditions. (Placing the pfd on main bus and avionics bus with fail over would improve redundancy too. Or having that aux heat on the 'non-essential' bus would have eliminated the risk too. 90 amp breakers might be nice too.)my perception of time during the troubleshooting was very off. I thought the event lasted quite a while; 20 minutes or more. However; when I looked at flight aware; I was shocked to discover that the total elapsed time from failure to restoration of one of the breakers was 6-7 minutes or less. I am glad in that dilation of time; I didn't elect to make a rash decision such as deviating and descending as I believe that would have made matters worse. Taking time to troubleshoot resulted in a favorable resolution.the incident also reinforced knowing the electrical systems (and all systems in general) well enough so as to conduct proper troubleshooting and to understand the knock-on implications of the loss of a particular bus (e.g.the potential for eventual engine power loss from inadequate fuel flow from the wing to the header tank due to loss of pumps). There is no 'bus failure' process in the abnormal procedures for the aircraft. So I; while I don't think it was difficult to figure out how to correct the issue (load shed is pretty obvious); I didn't have a written guide.I had been in a climb to FL260; so some amount of altitude was blocked by ATC; but while troubleshooting; my altitude peaked at FL25 before I returned to FL240 and maintained that altitude. ATC did not advise me of any issues with these altitude deviations; just requested I maintain my current heading; and were very cooperative and helpful during my troubleshooting.

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Original NASA ASRS Text

Title: PA46 pilot reported loss of dual main bus power; probably because of high electrical system demand in icing conditions.

Narrative: Climbing to cruising altitude at dusk (climbing back into the sunset; but IMC in clouds); the aircraft was passing through FL230 on the way to FL260; the aircraft suffered a dual main bus breaker failure. The plane was climbing through layers of IMC clouds; light ice; accordingly the electrical anti-ice/de-ice systems were on including windshield heat (always on above FL180); pitot heat (always on for all flights); stall warning heat; prop heat; and cabin electrical auxiliary heat for windshield defog. Systems on for much of the climb; but at some point either transient voltage greater than the dual 80 amp breakers could handle; or resistance on one breaker increased. Regardless of the cause; the result was a failure of numerous systems tied to the main bus including: Pilot's PFD/MFD (Garmin G500); Copilot Sandel EHSI failed; copilot electric Attitude Indicator (AI) probably spooled down (unclear and didn't check); all cabin illumination; wing to header tank fuel pumps; header tank to PT6A electrical boost pump; annunciator panel; all engine instruments (torque/temperature; fuel flow/pressure/quantity; oil temperature/pressure; vacuum pressure); all of the above mentioned anti/de-ice electrical systems; de-ice boot activation switch; p3 heat; and a bunch more that is not relevant to the situation. Dual GPS Nav/Comms (Avidyne IFD 540/440 with large map displays); radar; XM weather; traffic; transponder; and generator/battery volts/amp indicator continued to work worked. (Since the Nav/Comm and transponders were working; ATC communication was maintained and until I noted the issue to them; they were unaware of any problems.) The autopilot control head was illuminated; but without the AHRS from the G500; it wasn't functional.The pilot's backup instruments (airspeed; vacuum driven AI; and altimeter) were all functioning. Using the backup instruments; I maintained positive control of the aircraft while splitting my time to troubleshoot the problem. I advised ATC that I might need vectors to the nearest best weather; however; I did not want to immediately descend back into the much worse weather lower down (rain/snow/winds; low visibility). There was some wandering of heading and altitude during this period as I was forced to split focus between the instruments and checking breakers/etc using a flashlight. Shortly after the failure; I emerged out of the tops of the clouds in that area and in VMC conditions; and had no immediate icing concerns. With the loss of the wing fuel pumps to the header tank; I knew that although siphoning would continue to pull fuel to the header tank; it would be at a slower rate and fuel to the engine might eventually become an issue.The breakers would not initially reset since the electrical systems were all still on. However; after load-shedding some of the icing equipment via their individual circuit breakers --since the 'dead' control panel contains lighted push buttons (green dot light when on) without physical indication of whether they are on or off-- and waiting for a brief period; I was able to restore power to both main bus breakers. I was able to maintain an amp load below 70 amps for all electrical use (below the level of a single main breaker) in the plane with pitot and windshield heat on. I was actually enroute to the maintenance facility (for annual inspection); and much better weather was ahead at my destination than what was below. I elected to continue the trip and there were no further issues.In retrospect; this failure would not have happened had I not engaged the 'aux heat' which is an electric heater that warms the air coming out of the vent defog blower fan. That heater draws considerable amperage and I rarely have it on in active icing conditions. Generally that heater is on in high altitude cruise when it is too cold for icing; so only the pitot and windshield heaters are on when that is switched on. In those conditions the load is well below the 160 amp limit. It wasthe confluence of all the electrical systems engaged together with what may perhaps have been degraded breakers. I will recommend that the POH advise of high electrical loads in icing conditions. (Placing the PFD on main bus and avionics bus with fail over would improve redundancy too. Or having that Aux heat on the 'non-essential' bus would have eliminated the risk too. 90 amp breakers might be nice too.)My perception of time during the troubleshooting was very off. I thought the event lasted quite a while; 20 minutes or more. However; when I looked at Flight Aware; I was shocked to discover that the total elapsed time from failure to restoration of one of the breakers was 6-7 minutes or less. I am glad in that dilation of time; I didn't elect to make a rash decision such as deviating and descending as I believe that would have made matters worse. Taking time to troubleshoot resulted in a favorable resolution.The incident also reinforced knowing the electrical systems (and all systems in general) well enough so as to conduct proper troubleshooting and to understand the knock-on implications of the loss of a particular bus (e.g.the potential for eventual engine power loss from inadequate fuel flow from the wing to the header tank due to loss of pumps). There is no 'bus failure' process in the abnormal procedures for the aircraft. So I; while I don't think it was difficult to figure out how to correct the issue (load shed is pretty obvious); I didn't have a written guide.I had been in a climb to FL260; so some amount of altitude was blocked by ATC; but while troubleshooting; my altitude peaked at FL25 before I returned to FL240 and maintained that altitude. ATC did not advise me of any issues with these altitude deviations; just requested I maintain my current heading; and were very cooperative and helpful during my troubleshooting.

Data retrieved from NASA's ASRS site 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.