Narrative:

While flying east from mansfield, oh on 3/mon/91, we had noticed a very strong wave effect over the mountains of east oh, wv and md. And although I don't recall seeding any deviation greater than 250' on my altimeter, encoder errors plus minor differences in altimeter setting in the air and those expected by ATC computers might have caused me to be perceived to have broken my assigned altitude. I should have requested a block altitude sooner. On our return flight w-ward from bwi on 3/thurs/91, the conditions were much the same with added light to moderate (occasional) turbulence. I was highly preoccupied with trying to hold my altitude, and having anticipated the mountain waves, having some success. About 100 NM west of bwi, we experienced complete electrical failure. The voltage regulator for the altimeter had failed high causing a circuit breaker to pop and save the system. Exacerbating the problem was the fact that battery fluid was very low, so its capacity was badly impaired. Having lost communication with center, we proceeded VFR to the nearest airport, landed, had the regulator replaced and 2 days later continued. I do not recall (nor does my wife) seeing the alternator warning light before the total failure, nor did I see the alternator current at 0. We were very occupied with the turbulence. The lesson learned is to not allow things like turbulence to distract one from a full and cognitive scan of all the INS. Exacerbating the poor engine INS scan was the fact that my yoke board restricts the view of those INS. It has already been modified to correct that.

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Original NASA ASRS Text

Title: LOW TIME SMA PLT USES LOST COM PROC WHEN HIS ACFT SUFFERS FROM PRIMARY ELECTRICAL SUPPLY PROBLEM.

Narrative: WHILE FLYING E FROM MANSFIELD, OH ON 3/MON/91, WE HAD NOTICED A VERY STRONG WAVE EFFECT OVER THE MOUNTAINS OF E OH, WV AND MD. AND ALTHOUGH I DON'T RECALL SEEDING ANY DEVIATION GREATER THAN 250' ON MY ALTIMETER, ENCODER ERRORS PLUS MINOR DIFFERENCES IN ALTIMETER SETTING IN THE AIR AND THOSE EXPECTED BY ATC COMPUTERS MIGHT HAVE CAUSED ME TO BE PERCEIVED TO HAVE BROKEN MY ASSIGNED ALT. I SHOULD HAVE REQUESTED A BLOCK ALT SOONER. ON OUR RETURN FLT W-WARD FROM BWI ON 3/THURS/91, THE CONDITIONS WERE MUCH THE SAME WITH ADDED LIGHT TO MODERATE (OCCASIONAL) TURB. I WAS HIGHLY PREOCCUPIED WITH TRYING TO HOLD MY ALT, AND HAVING ANTICIPATED THE MOUNTAIN WAVES, HAVING SOME SUCCESS. ABOUT 100 NM W OF BWI, WE EXPERIENCED COMPLETE ELECTRICAL FAILURE. THE VOLTAGE REGULATOR FOR THE ALTIMETER HAD FAILED HIGH CAUSING A CB TO POP AND SAVE THE SYS. EXACERBATING THE PROB WAS THE FACT THAT BATTERY FLUID WAS VERY LOW, SO ITS CAPACITY WAS BADLY IMPAIRED. HAVING LOST COM WITH CENTER, WE PROCEEDED VFR TO THE NEAREST ARPT, LANDED, HAD THE REGULATOR REPLACED AND 2 DAYS LATER CONTINUED. I DO NOT RECALL (NOR DOES MY WIFE) SEEING THE ALTERNATOR WARNING LIGHT BEFORE THE TOTAL FAILURE, NOR DID I SEE THE ALTERNATOR CURRENT AT 0. WE WERE VERY OCCUPIED WITH THE TURB. THE LESSON LEARNED IS TO NOT ALLOW THINGS LIKE TURB TO DISTRACT ONE FROM A FULL AND COGNITIVE SCAN OF ALL THE INS. EXACERBATING THE POOR ENG INS SCAN WAS THE FACT THAT MY YOKE BOARD RESTRICTS THE VIEW OF THOSE INS. IT HAS ALREADY BEEN MODIFIED TO CORRECT THAT.

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.