Narrative:

Upon initial climb out of sun valley in light snow on an IFR flight plan, engine began running very rough, missing and sputtering. Because of WX and terrain, return to ksun was not deemed feasible so pilot continued climb to assigned altitude of 9000 ft MSL en route to destination/nearest airport, twin falls. Upon reaching assigned altitude, engines were running smoothly and within normal operating limits. Shortly after making contact with approach control, aircraft suffered complete electrical failure cutting off communications and navigation equipment in IMC. Pilot climbed to 11000 ft for terrain clearance finding VMC between layers. Handheld radio was on board and partial communications and navigation was restored. Although pilot squawked 7700, it is not believed that approach control received because of electrical problem and non radar environment. Because approach into twf would have required flying into IMC with only limited reliability on partially restored electronics, pilot requested and was granted deviation on IFR flight plan to las vegas, mcclellen, the nearest airport with VFR and clear skies. Prior to receiving clearance to las, aircraft circled over twf, probably off airway and in conflict with original clearance. When cleared for ILS approach into twf, pilot declined. En route to las, gradually climbed to 17000 ft to avoid WX. Flight thereafter went somewhat routine except for one deviation from assigned altitude of 17000 ft down to approximately 15500 ft due to ice and WX. Aircraft flown was a cessna 340A. Probable cause of engine problem: because engines ultimately smoothed out, pilot surmises problem may have been caused by ice particles suspended in fuel and ingested during initial climb. Although aircraft engines were preheated and ran normally during runup, fuel in wings could have been below or at freezing temperatures. Problem probably could have been avoided through use of de-ice additive to fuel. As of the date of this report, electrical problem has not been diagnosed. Contributing factors may have been high electrical loads through preventive use of de-icing equipment. Partial electrical was eventually restored through reset of alternator circuits and alternating between system on at any one time. Availability of a handheld radio is considered by this pilot to be an important part of safety equipment. It doesn't do a great deal of good, however, unless the battery is fully charged. Ours was low, and so it would only be used sparingly.

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Original NASA ASRS Text

Title: PVT PLT OF A C340 ACFT LEFT ASSIGNED ALT DUE TO INFLT ENCOUNTER WITH ICING WX CONDITIONS AND HAD COMPLETE PRIMARY ELECTRICAL SUPPLY PROB.

Narrative: UPON INITIAL CLB OUT OF SUN VALLEY IN LIGHT SNOW ON AN IFR FLT PLAN, ENG BEGAN RUNNING VERY ROUGH, MISSING AND SPUTTERING. BECAUSE OF WX AND TERRAIN, RETURN TO KSUN WAS NOT DEEMED FEASIBLE SO PLT CONTINUED CLB TO ASSIGNED ALT OF 9000 FT MSL ENRTE TO DEST/NEAREST ARPT, TWIN FALLS. UPON REACHING ASSIGNED ALT, ENGS WERE RUNNING SMOOTHLY AND WITHIN NORMAL OPERATING LIMITS. SHORTLY AFTER MAKING CONTACT WITH APCH CTL, ACFT SUFFERED COMPLETE ELECTRICAL FAILURE CUTTING OFF COMS AND NAV EQUIP IN IMC. PLT CLBED TO 11000 FT FOR TERRAIN CLRNC FINDING VMC BTWN LAYERS. HANDHELD RADIO WAS ON BOARD AND PARTIAL COMS AND NAV WAS RESTORED. ALTHOUGH PLT SQUAWKED 7700, IT IS NOT BELIEVED THAT APCH CTL RECEIVED BECAUSE OF ELECTRICAL PROB AND NON RADAR ENVIRONMENT. BECAUSE APCH INTO TWF WOULD HAVE REQUIRED FLYING INTO IMC WITH ONLY LIMITED RELIABILITY ON PARTIALLY RESTORED ELECTRONICS, PLT REQUESTED AND WAS GRANTED DEV ON IFR FLT PLAN TO LAS VEGAS, MCCLELLEN, THE NEAREST ARPT WITH VFR AND CLR SKIES. PRIOR TO RECEIVING CLRNC TO LAS, ACFT CIRCLED OVER TWF, PROBABLY OFF AIRWAY AND IN CONFLICT WITH ORIGINAL CLRNC. WHEN CLRED FOR ILS APCH INTO TWF, PLT DECLINED. ENRTE TO LAS, GRADUALLY CLBED TO 17000 FT TO AVOID WX. FLT THEREAFTER WENT SOMEWHAT ROUTINE EXCEPT FOR ONE DEV FROM ASSIGNED ALT OF 17000 FT DOWN TO APPROX 15500 FT DUE TO ICE AND WX. ACFT FLOWN WAS A CESSNA 340A. PROBABLE CAUSE OF ENG PROB: BECAUSE ENGS ULTIMATELY SMOOTHED OUT, PLT SURMISES PROB MAY HAVE BEEN CAUSED BY ICE PARTICLES SUSPENDED IN FUEL AND INGESTED DURING INITIAL CLB. ALTHOUGH ACFT ENGS WERE PREHEATED AND RAN NORMALLY DURING RUNUP, FUEL IN WINGS COULD HAVE BEEN BELOW OR AT FREEZING TEMPS. PROB PROBABLY COULD HAVE BEEN AVOIDED THROUGH USE OF DE-ICE ADDITIVE TO FUEL. AS OF THE DATE OF THIS RPT, ELECTRICAL PROB HAS NOT BEEN DIAGNOSED. CONTRIBUTING FACTORS MAY HAVE BEEN HIGH ELECTRICAL LOADS THROUGH PREVENTIVE USE OF DE-ICING EQUIP. PARTIAL ELECTRICAL WAS EVENTUALLY RESTORED THROUGH RESET OF ALTERNATOR CIRCUITS AND ALTERNATING BTWN SYS ON AT ANY ONE TIME. AVAILABILITY OF A HANDHELD RADIO IS CONSIDERED BY THIS PLT TO BE AN IMPORTANT PART OF SAFETY EQUIP. IT DOESN'T DO A GREAT DEAL OF GOOD, HOWEVER, UNLESS THE BATTERY IS FULLY CHARGED. OURS WAS LOW, AND SO IT WOULD ONLY BE USED SPARINGLY.

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.