Narrative:

The second incident experienced during this flight was communication difficulty which resulted from equipment failure on my aircraft. I had difficulty starting the aircraft due to a weak battery. On run up check the amp meter indicated normal operation of the alternator so I had no reason to suspect further difficulty. Although I did not detect it at the time, the weak battery and possible low charge rate may have been effecting my communications equipment at the time I was preparing to depart. Immediately after departure I attempted to contact tower to request a turn on course. Tower did not respond and on my second attempt I noticed that my transmission did not sound normal. I switched radios and tried again but noticed the same indication that I was not getting out. I then heard tower talking to another aircraft but the reception was weak and barely readable. Realizing I had a probable low voltage condition I turned off all electrical equipment except the transponder and my #1 communication radio. I was immediately able to contact tower and was instructed to make left traffic and contact departure when established on crosswind. I do not believe I missed any communications with tower. After completing the left turn I continued to trouble-shoot the problem and called departure. My initial contact with departure was difficult and required several exchanges to establish radar contact and obtain on course instructions. Eventually I was able to get the alternator on line and confirm it's operation by a position deflection of the amp meter indicator. Believing my problem was resolved I decided to continue to my destination. Communications with departure remained strong and normal until I was given frequency change about 25 mi out from mfe. I contacted san angelo FSS and opened my VFR flight plan. Approximately 2/3 of the way to laredo (lrd), my destination, I turned on a VOR receiver. No signal reception was indicated. I attempted to contact FSS without success. Realizing I may arrive at lrd without communication capability I reviewed the VFR sectional for alternatives but found none where ground communications would be available. I turned off all electrical equipment in hope that enough power might be conserved to make initial contact at lrd. Upon arriving at lrd I turned the communication radio on and attempted to contact the tower. When I was unable to make contact I continued inbound observing for traffic. I detected an aircraft departing runway 17 so I descended to traffic pattern altitude, approached at a 45 degree angle to runway 17, made left hand traffic, observing the tower for light signals and landed on runway 17. This problem was caused by equipment failure and inadequate system condition indicators. The aircraft was a PA-28-181. The amp meter on this particular aircraft normally has a very low amp meter indication, usually less than 1 needle width above zero unless fully loaded with all electrical system including pitot heat. The altitude caution light is mounted on the instrument panel just below a glare shield and is a button type with back lighted letters. In daylight it is virtually impossible to detect whether or not this light is illuminated. This problem can be resolved by installation of a different amp meter which will give a more prominent indication of charging condition and installation of an altitude failure caution light better than the weak back lighted button type which is currently installed.

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Original NASA ASRS Text

Title: RADIO COM PROB NOTWITHSTANDING. ATX PLT CONTINUES TO DEST ARPT. CITES ACFT ELECTRICAL ELECTRONIC PANEL DESIGN PROB.

Narrative: THE SECOND INCIDENT EXPERIENCED DURING THIS FLT WAS COM DIFFICULTY WHICH RESULTED FROM EQUIP FAILURE ON MY ACFT. I HAD DIFFICULTY STARTING THE ACFT DUE TO A WEAK BATTERY. ON RUN UP CHK THE AMP METER INDICATED NORMAL OP OF THE ALTERNATOR SO I HAD NO REASON TO SUSPECT FURTHER DIFFICULTY. ALTHOUGH I DID NOT DETECT IT AT THE TIME, THE WEAK BATTERY AND POSSIBLE LOW CHARGE RATE MAY HAVE BEEN EFFECTING MY COMS EQUIP AT THE TIME I WAS PREPARING TO DEPART. IMMEDIATELY AFTER DEP I ATTEMPTED TO CONTACT TWR TO REQUEST A TURN ON COURSE. TWR DID NOT RESPOND AND ON MY SECOND ATTEMPT I NOTICED THAT MY XMISSION DID NOT SOUND NORMAL. I SWITCHED RADIOS AND TRIED AGAIN BUT NOTICED THE SAME INDICATION THAT I WAS NOT GETTING OUT. I THEN HEARD TWR TALKING TO ANOTHER ACFT BUT THE RECEPTION WAS WEAK AND BARELY READABLE. REALIZING I HAD A PROBABLE LOW VOLTAGE CONDITION I TURNED OFF ALL ELECTRICAL EQUIP EXCEPT THE XPONDER AND MY #1 COM RADIO. I WAS IMMEDIATELY ABLE TO CONTACT TWR AND WAS INSTRUCTED TO MAKE L TFC AND CONTACT DEP WHEN ESTABLISHED ON XWIND. I DO NOT BELIEVE I MISSED ANY COMS WITH TWR. AFTER COMPLETING THE L TURN I CONTINUED TO TROUBLE-SHOOT THE PROB AND CALLED DEP. MY INITIAL CONTACT WITH DEP WAS DIFFICULT AND REQUIRED SEVERAL EXCHANGES TO ESTABLISH RADAR CONTACT AND OBTAIN ON COURSE INSTRUCTIONS. EVENTUALLY I WAS ABLE TO GET THE ALTERNATOR ON LINE AND CONFIRM IT'S OP BY A POS DEFLECTION OF THE AMP METER INDICATOR. BELIEVING MY PROB WAS RESOLVED I DECIDED TO CONTINUE TO MY DEST. COMS WITH DEP REMAINED STRONG AND NORMAL UNTIL I WAS GIVEN FREQ CHANGE ABOUT 25 MI OUT FROM MFE. I CONTACTED SAN ANGELO FSS AND OPENED MY VFR FLT PLAN. APPROX 2/3 OF THE WAY TO LAREDO (LRD), MY DEST, I TURNED ON A VOR RECEIVER. NO SIGNAL RECEPTION WAS INDICATED. I ATTEMPTED TO CONTACT FSS WITHOUT SUCCESS. REALIZING I MAY ARRIVE AT LRD WITHOUT COM CAPABILITY I REVIEWED THE VFR SECTIONAL FOR ALTERNATIVES BUT FOUND NONE WHERE GND COMS WOULD BE AVAILABLE. I TURNED OFF ALL ELECTRICAL EQUIP IN HOPE THAT ENOUGH PWR MIGHT BE CONSERVED TO MAKE INITIAL CONTACT AT LRD. UPON ARRIVING AT LRD I TURNED THE COM RADIO ON AND ATTEMPTED TO CONTACT THE TWR. WHEN I WAS UNABLE TO MAKE CONTACT I CONTINUED INBOUND OBSERVING FOR TFC. I DETECTED AN ACFT DEPARTING RWY 17 SO I DSNDED TO TFC PATTERN ALT, APCHED AT A 45 DEG ANGLE TO RWY 17, MADE L HAND TFC, OBSERVING THE TWR FOR LIGHT SIGNALS AND LANDED ON RWY 17. THIS PROB WAS CAUSED BY EQUIP FAILURE AND INADEQUATE SYS CONDITION INDICATORS. THE ACFT WAS A PA-28-181. THE AMP METER ON THIS PARTICULAR ACFT NORMALLY HAS A VERY LOW AMP METER INDICATION, USUALLY LESS THAN 1 NEEDLE WIDTH ABOVE ZERO UNLESS FULLY LOADED WITH ALL ELECTRICAL SYS INCLUDING PITOT HEAT. THE ALT CAUTION LIGHT IS MOUNTED ON THE INST PANEL JUST BELOW A GLARE SHIELD AND IS A BUTTON TYPE WITH BACK LIGHTED LETTERS. IN DAYLIGHT IT IS VIRTUALLY IMPOSSIBLE TO DETECT WHETHER OR NOT THIS LIGHT IS ILLUMINATED. THIS PROB CAN BE RESOLVED BY INSTALLATION OF A DIFFERENT AMP METER WHICH WILL GIVE A MORE PROMINENT INDICATION OF CHARGING CONDITION AND INSTALLATION OF AN ALT FAILURE CAUTION LIGHT BETTER THAN THE WEAK BACK LIGHTED BUTTON TYPE WHICH IS CURRENTLY INSTALLED.

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.