Narrative:

Checked in with approach; descended to 3000 ft on the arrival. Leaving the last fix; I was cleared 2000 ft; direct intersection and expect the GPS approach. AAA airport was reporting 700 ft overcast; wind 020 degrees at 9 KTS. At 3000 ft; autoplt was chasing +/-100 ft. Turned off altitude hold; hand flew level. Hmmmm; no concern seen it happen before; but wait -- only at gross and high altitude. Hindsight. As I was almost abeam the field; with about 20 mi to go (south to initial fix then turn inbound) the CNX80 GPS flashed 'unable to command transponder.' hmmmm. Couldn't recycle. Next; I noted the GPS light on the CDI was very dim. Hmmmm. Next; the GPS display flickered several times. Ehhh? Maybe the brightness from in and out of clouds. Never see it change that fast. Hmmmm. Now; about 3 mi southwest of airport; famous aviation quote 'why is that doing that?' then; communication #2 (radio) went blank. My worst nightmare is coming true. I brag I can lose gyros and vacuum because autoplt is electric. But; lose electricity; no autoplt no radio; no navigation of any kind. In IMC. Approach to minimums. Training kicked in. Ammeter looked zero (bear in mind the square gauge has 3 markings; 0; at 1/2 way 35 amp; at right 75 amp. I am used to seeing it around 10-ish (close to zero). I shut down all electrical system except the GPS. I keyed the microphone and said 'pan pan' no transmit light. No transponder to squawk 7600. No radio to call. (GPS is smart; saved energy during the emergency by not transmitting.) decision time. I could hear approach keep calling me. I knew I had a bizjet following me #2 for the approach. I have a dim line showing position and final approach course on the GPS. Do I follow regulations? Fly to intersection as expected; then fly the approach? I declared an emergency and immediately turned to the final fix. No reason to prolong flight an extra 7-10 mins. I heard approach tell the bizjets (2 now) fly vectors 180 degrees; we have a missing aircraft over intersection. The CDI didn't work; best I could do was fly the airplane symbol over the course line on the GPS. I broke out right at 700 ft; about 1000 ft southeast of the runway. What a beautiful sight of bright lights. I flashed my landing light at the tower; that was enough to kill the GPS. (Who cares at this point?) never saw green light from tower; again who cares? Taxied to parking; deplaned. It now looks like I lost the alternator. Looks like I flew almost 2 hours on battery (gill sealed; pay extra for it!). Have the plane towed to the mechanics. Open cowling; problem found instantly. The (probably $1.00) part; lug that attaches the battery wire to the alternator had broken off; after 1200 hours of service. Charged the battery; fixed the wire; probably got off for under $70. Started right up; showed 35 amp charge. Lessons learned: from now on; I will keep my handheld garmin GPS 196 (with approachs) and plenty of batteries in the aircraft.

Related reports:

Google
 

Original NASA ASRS Text

Title: PA28 PLT HAS ELECTRICAL FAILURE IN IMC DURING APCH WITH LOSS OF COM AND NAV EQUIP; DECLARES AN EMER.

Narrative: CHKED IN WITH APCH; DSNDED TO 3000 FT ON THE ARR. LEAVING THE LAST FIX; I WAS CLRED 2000 FT; DIRECT INTXN AND EXPECT THE GPS APCH. AAA ARPT WAS RPTING 700 FT OVCST; WIND 020 DEGS AT 9 KTS. AT 3000 FT; AUTOPLT WAS CHASING +/-100 FT. TURNED OFF ALT HOLD; HAND FLEW LEVEL. HMMMM; NO CONCERN SEEN IT HAPPEN BEFORE; BUT WAIT -- ONLY AT GROSS AND HIGH ALT. HINDSIGHT. AS I WAS ALMOST ABEAM THE FIELD; WITH ABOUT 20 MI TO GO (S TO INITIAL FIX THEN TURN INBOUND) THE CNX80 GPS FLASHED 'UNABLE TO COMMAND XPONDER.' HMMMM. COULDN'T RECYCLE. NEXT; I NOTED THE GPS LIGHT ON THE CDI WAS VERY DIM. HMMMM. NEXT; THE GPS DISPLAY FLICKERED SEVERAL TIMES. EHHH? MAYBE THE BRIGHTNESS FROM IN AND OUT OF CLOUDS. NEVER SEE IT CHANGE THAT FAST. HMMMM. NOW; ABOUT 3 MI SW OF ARPT; FAMOUS AVIATION QUOTE 'WHY IS THAT DOING THAT?' THEN; COM #2 (RADIO) WENT BLANK. MY WORST NIGHTMARE IS COMING TRUE. I BRAG I CAN LOSE GYROS AND VACUUM BECAUSE AUTOPLT IS ELECTRIC. BUT; LOSE ELECTRICITY; NO AUTOPLT NO RADIO; NO NAV OF ANY KIND. IN IMC. APCH TO MINIMUMS. TRAINING KICKED IN. AMMETER LOOKED ZERO (BEAR IN MIND THE SQUARE GAUGE HAS 3 MARKINGS; 0; AT 1/2 WAY 35 AMP; AT R 75 AMP. I AM USED TO SEEING IT AROUND 10-ISH (CLOSE TO ZERO). I SHUT DOWN ALL ELECTRICAL SYS EXCEPT THE GPS. I KEYED THE MIKE AND SAID 'PAN PAN' NO XMIT LIGHT. NO XPONDER TO SQUAWK 7600. NO RADIO TO CALL. (GPS IS SMART; SAVED ENERGY DURING THE EMER BY NOT XMITTING.) DECISION TIME. I COULD HEAR APCH KEEP CALLING ME. I KNEW I HAD A BIZJET FOLLOWING ME #2 FOR THE APCH. I HAVE A DIM LINE SHOWING POS AND FINAL APCH COURSE ON THE GPS. DO I FOLLOW REGS? FLY TO INTXN AS EXPECTED; THEN FLY THE APCH? I DECLARED AN EMER AND IMMEDIATELY TURNED TO THE FINAL FIX. NO REASON TO PROLONG FLT AN EXTRA 7-10 MINS. I HEARD APCH TELL THE BIZJETS (2 NOW) FLY VECTORS 180 DEGS; WE HAVE A MISSING ACFT OVER INTXN. THE CDI DIDN'T WORK; BEST I COULD DO WAS FLY THE AIRPLANE SYMBOL OVER THE COURSE LINE ON THE GPS. I BROKE OUT R AT 700 FT; ABOUT 1000 FT SE OF THE RWY. WHAT A BEAUTIFUL SIGHT OF BRIGHT LIGHTS. I FLASHED MY LNDG LIGHT AT THE TWR; THAT WAS ENOUGH TO KILL THE GPS. (WHO CARES AT THIS POINT?) NEVER SAW GREEN LIGHT FROM TWR; AGAIN WHO CARES? TAXIED TO PARKING; DEPLANED. IT NOW LOOKS LIKE I LOST THE ALTERNATOR. LOOKS LIKE I FLEW ALMOST 2 HRS ON BATTERY (GILL SEALED; PAY EXTRA FOR IT!). HAVE THE PLANE TOWED TO THE MECHS. OPEN COWLING; PROB FOUND INSTANTLY. THE (PROBABLY $1.00) PART; LUG THAT ATTACHES THE BATTERY WIRE TO THE ALTERNATOR HAD BROKEN OFF; AFTER 1200 HRS OF SVC. CHARGED THE BATTERY; FIXED THE WIRE; PROBABLY GOT OFF FOR UNDER $70. STARTED RIGHT UP; SHOWED 35 AMP CHARGE. LESSONS LEARNED: FROM NOW ON; I WILL KEEP MY HANDHELD GARMIN GPS 196 (WITH APCHS) AND PLENTY OF BATTERIES IN THE ACFT.

Data retrieved from NASA's ASRS site as of January 2009 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.