Narrative:

I completed my checklist; including a complete run-up; and with all gauges; including the alternator load meter showing normal indications. I received takeoff clearance; acknowledged the clearance; and started my takeoff roll. Just before rotation; I received another call from the tower clearing me for takeoff; which I again acknowledged; thinking my original acknowledgement had been blocked by another radio transmission. When airborne; I heard 1 or 2 more calls from the tower; and I realized that they were unable to copy my xmissions. Soon afterward the radios began to put out a lot of noise; with no intelligible audio. At that point it became clear that I had experienced radio failure. While I had indicated to clearance delivery before taxi that I was requesting an initial altitude of 2000 ft; I stayed low at 600 ft to exit the class 'C' airspace as soon as possible. When I was out of the airspace; I checked the aircraft voltage with a small digital multimeter I carry; and found that it had dropped to approximately 9 volts on a 14 volt system with a 12 volt battery; which explained the radio failures. This was even with a charge indicating on the original piper installed load meter. I tried to determine why the battery would be low with the alternator still showing a charge. I believe the alternator was actually still charging as indicated; and it was doing so at the lower amount that would be consistent with the load that a charged battery and normal system loads would require. I realized however that I was experiencing a net discharge due to the alternator not keeping up with the electrical load that existed at the time; even though it was attempting to. A cessna type charge-discharge meter would have shown a net discharge; and would have been immediately noticeable; but the piper load meter just shows alternator output. Unless a voltmeter is also installed; the pilot has no way of knowing if that indicated output is adequate for the electrical load; even with output showing. This of course; would not be a problem with a total failure of the alternator as there would be zero alternator output indicated; but a partial failure; which is not uncommon; could result in the pilot not realizing what was happening. An additional clue was that one of the radios had some receiver background noise that was not quite normal; even though it was still receiving and transmitting satisfactorily up to the total failure. After understanding that I only had partial alternator output; I reduced electrical load; and the voltage on the battery came back up; and I was able to complete my trip with normal radio communications. At the first opportunity; I called FSS and had them relay to the tower that I had experienced an electrical failure and that we were ok. They relayed back that they appreciated the information; since we had stayed low and they had lost radar contact. They probably didn't see the transponder since it probably also failed due to low electrical system voltage. Subsequent maintenance revealed that the alternator brushes were worn; explaining the reduced alternator output. It is also of interest that we had backup in the form of a handheld battery pwred GPS; and a handheld communications/VOR navigation radio. However; by the time the hand held radio was accessed and used; we were beyond its range to communicate with the tower.

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Original NASA ASRS Text

Title: A PIPER PA-32-300 ACFT PILOT EXPERIENCED RADIO COMMUNICATION PROBLEMS SHORTLY AFTER TAKEOFF.

Narrative: I COMPLETED MY CHKLIST; INCLUDING A COMPLETE RUN-UP; AND WITH ALL GAUGES; INCLUDING THE ALTERNATOR LOAD METER SHOWING NORMAL INDICATIONS. I RECEIVED TKOF CLRNC; ACKNOWLEDGED THE CLRNC; AND STARTED MY TKOF ROLL. JUST BEFORE ROTATION; I RECEIVED ANOTHER CALL FROM THE TWR CLRING ME FOR TKOF; WHICH I AGAIN ACKNOWLEDGED; THINKING MY ORIGINAL ACKNOWLEDGEMENT HAD BEEN BLOCKED BY ANOTHER RADIO XMISSION. WHEN AIRBORNE; I HEARD 1 OR 2 MORE CALLS FROM THE TWR; AND I REALIZED THAT THEY WERE UNABLE TO COPY MY XMISSIONS. SOON AFTERWARD THE RADIOS BEGAN TO PUT OUT A LOT OF NOISE; WITH NO INTELLIGIBLE AUDIO. AT THAT POINT IT BECAME CLR THAT I HAD EXPERIENCED RADIO FAILURE. WHILE I HAD INDICATED TO CLRNC DELIVERY BEFORE TAXI THAT I WAS REQUESTING AN INITIAL ALT OF 2000 FT; I STAYED LOW AT 600 FT TO EXIT THE CLASS 'C' AIRSPACE ASAP. WHEN I WAS OUT OF THE AIRSPACE; I CHKED THE ACFT VOLTAGE WITH A SMALL DIGITAL MULTIMETER I CARRY; AND FOUND THAT IT HAD DROPPED TO APPROX 9 VOLTS ON A 14 VOLT SYS WITH A 12 VOLT BATTERY; WHICH EXPLAINED THE RADIO FAILURES. THIS WAS EVEN WITH A CHARGE INDICATING ON THE ORIGINAL PIPER INSTALLED LOAD METER. I TRIED TO DETERMINE WHY THE BATTERY WOULD BE LOW WITH THE ALTERNATOR STILL SHOWING A CHARGE. I BELIEVE THE ALTERNATOR WAS ACTUALLY STILL CHARGING AS INDICATED; AND IT WAS DOING SO AT THE LOWER AMOUNT THAT WOULD BE CONSISTENT WITH THE LOAD THAT A CHARGED BATTERY AND NORMAL SYS LOADS WOULD REQUIRE. I REALIZED HOWEVER THAT I WAS EXPERIENCING A NET DISCHARGE DUE TO THE ALTERNATOR NOT KEEPING UP WITH THE ELECTRICAL LOAD THAT EXISTED AT THE TIME; EVEN THOUGH IT WAS ATTEMPTING TO. A CESSNA TYPE CHARGE-DISCHARGE METER WOULD HAVE SHOWN A NET DISCHARGE; AND WOULD HAVE BEEN IMMEDIATELY NOTICEABLE; BUT THE PIPER LOAD METER JUST SHOWS ALTERNATOR OUTPUT. UNLESS A VOLTMETER IS ALSO INSTALLED; THE PLT HAS NO WAY OF KNOWING IF THAT INDICATED OUTPUT IS ADEQUATE FOR THE ELECTRICAL LOAD; EVEN WITH OUTPUT SHOWING. THIS OF COURSE; WOULD NOT BE A PROB WITH A TOTAL FAILURE OF THE ALTERNATOR AS THERE WOULD BE ZERO ALTERNATOR OUTPUT INDICATED; BUT A PARTIAL FAILURE; WHICH IS NOT UNCOMMON; COULD RESULT IN THE PLT NOT REALIZING WHAT WAS HAPPENING. AN ADDITIONAL CLUE WAS THAT ONE OF THE RADIOS HAD SOME RECEIVER BACKGROUND NOISE THAT WAS NOT QUITE NORMAL; EVEN THOUGH IT WAS STILL RECEIVING AND XMITTING SATISFACTORILY UP TO THE TOTAL FAILURE. AFTER UNDERSTANDING THAT I ONLY HAD PARTIAL ALTERNATOR OUTPUT; I REDUCED ELECTRICAL LOAD; AND THE VOLTAGE ON THE BATTERY CAME BACK UP; AND I WAS ABLE TO COMPLETE MY TRIP WITH NORMAL RADIO COMS. AT THE FIRST OPPORTUNITY; I CALLED FSS AND HAD THEM RELAY TO THE TWR THAT I HAD EXPERIENCED AN ELECTRICAL FAILURE AND THAT WE WERE OK. THEY RELAYED BACK THAT THEY APPRECIATED THE INFO; SINCE WE HAD STAYED LOW AND THEY HAD LOST RADAR CONTACT. THEY PROBABLY DIDN'T SEE THE XPONDER SINCE IT PROBABLY ALSO FAILED DUE TO LOW ELECTRICAL SYS VOLTAGE. SUBSEQUENT MAINT REVEALED THAT THE ALTERNATOR BRUSHES WERE WORN; EXPLAINING THE REDUCED ALTERNATOR OUTPUT. IT IS ALSO OF INTEREST THAT WE HAD BACKUP IN THE FORM OF A HANDHELD BATTERY PWRED GPS; AND A HANDHELD COMS/VOR NAV RADIO. HOWEVER; BY THE TIME THE HAND HELD RADIO WAS ACCESSED AND USED; WE WERE BEYOND ITS RANGE TO COMMUNICATE WITH THE TWR.

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.