C172 pilot had electrical failure.

Attributes
ACN	464990
Time
Date	200002
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : lit.airport
State Reference	AR
Altitude	msl single value : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lit.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	None
Person 1
Affiliation	other
Function	flight crew : single pilot oversight : pic
Qualification	pilot : private
Experience	flight time last 90 days : 35 flight time total : 1500 flight time type : 500
ASRS Report	464990
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical incursion : landing without clearance other anomaly other
Independent Detector	other controllera other controllerb other flight crewa
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During contact with lit approach control on 119.5, the controller notified me that he was not receiving transponder, please reset. I noticed as I reached over to do actual reset that the lights on the transponder were dim, including power and interrogation. It was then I noticed electrical discharge only on my ammeter. I had already been given 'expect runway 18' clearance and I had been listening to traffic on the frequency. Although I could not raise approach on radio #1, or tower on #2, I was in a position to finish the approach and landing without adversely effecting either approaching or departing traffic on runway 18. I turned off all power usage except #1 radio, but still could not reach ATC. I reported short final, then clear of runway 18, then I taxied to parking. I'm not certain if I ever received a light from the tower. Corrective actions: I am making a scan of voltmeter as a standard periodic part of monitoring aircraft system and I am having the battery charging system reviewed by a mechanic. The incipient loss of electrical power is not obvious to a pilot who is not looking for specific signs. An additional remedy would be to carry a backup hand-held transmitter. I tried after landing to phone the tower to explain what occurred but all I could get was an answering machine. I did not leave a message. I have had my favorite mechanic check out the airplane and he found the problem to be a broken bracket that holds the alternator in place.

Original NASA ASRS Text

Title: C172 PLT HAD ELECTRICAL FAILURE.

Narrative: DURING CONTACT WITH LIT APCH CTL ON 119.5, THE CTLR NOTIFIED ME THAT HE WAS NOT RECEIVING XPONDER, PLEASE RESET. I NOTICED AS I REACHED OVER TO DO ACTUAL RESET THAT THE LIGHTS ON THE XPONDER WERE DIM, INCLUDING PWR AND INTERROGATION. IT WAS THEN I NOTICED ELECTRICAL DISCHARGE ONLY ON MY AMMETER. I HAD ALREADY BEEN GIVEN 'EXPECT RWY 18' CLRNC AND I HAD BEEN LISTENING TO TFC ON THE FREQ. ALTHOUGH I COULD NOT RAISE APCH ON RADIO #1, OR TWR ON #2, I WAS IN A POS TO FINISH THE APCH AND LNDG WITHOUT ADVERSELY EFFECTING EITHER APCHING OR DEPARTING TFC ON RWY 18. I TURNED OFF ALL PWR USAGE EXCEPT #1 RADIO, BUT STILL COULD NOT REACH ATC. I RPTED SHORT FINAL, THEN CLR OF RWY 18, THEN I TAXIED TO PARKING. I'M NOT CERTAIN IF I EVER RECEIVED A LIGHT FROM THE TWR. CORRECTIVE ACTIONS: I AM MAKING A SCAN OF VOLTMETER AS A STANDARD PERIODIC PART OF MONITORING ACFT SYS AND I AM HAVING THE BATTERY CHARGING SYS REVIEWED BY A MECH. THE INCIPIENT LOSS OF ELECTRICAL PWR IS NOT OBVIOUS TO A PLT WHO IS NOT LOOKING FOR SPECIFIC SIGNS. AN ADDITIONAL REMEDY WOULD BE TO CARRY A BACKUP HAND-HELD XMITTER. I TRIED AFTER LNDG TO PHONE THE TWR TO EXPLAIN WHAT OCCURRED BUT ALL I COULD GET WAS AN ANSWERING MACHINE. I DID NOT LEAVE A MESSAGE. I HAVE HAD MY FAVORITE MECH CHK OUT THE AIRPLANE AND HE FOUND THE PROB TO BE A BROKEN BRACKET THAT HOLDS THE ALTERNATOR IN PLACE.

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.