Narrative:

While taking a local VFR flight in clear skies in the denver metropolitan area, my aircraft suffered a complete electrical system failure. All system were lost including both radios, ADF, and transponder. I detected the onset of the failure by noticing the gradual dimming of the radio frequency display lights. Shortly thereafter, (ie, mins) all electrical system went dark. After an estimated 5-10 mins of troubleshooting on my part, I determined that I was not going to restore power. I would have to return to centennial report for landing without obtaining the current ATIS information or being in radio contact the control tower. I did not intend to operate on battery power any longer than necessary. I entered the class D airspace in an area and at an altitude typical of airport traffic and proceeded to approach the airport area. When approximately 2-3 mi from the airport, I signaled the control tower by waving (ie, rolling) my wings in a fashion designed to indicate that my aircraft had a problem. At that time I had the control tower in clear view. I studied the tower carefully for light signals but received none. After having determined that there appeared to be no aircraft in the traffic pattern for runway 17R, I entered the runway 17R pattern downwind midfield at pattern altitude. During the downwind phase I constantly monitored the tower for signals but received none. I continued with the approach, turned base and final without any indication of light signals from the control tower. At that point I committed the aircraft for landing and proceeded to land without receiving an authorizing light signal. At any given time, centennial airport is quite busy and it is especially busy at that time of the morning. In my judgement, although I had received neither clearance nor denial to land, it was safer for me to complete the landing than to go around and wait for an authorizing signal (which I was unsure as to whether I would receive or not). Conditions at that moment were extremely favorable as there were no other aircraft (that I could see) in the pattern or on the ground in the immediate vicinity of my intended runway. After completion of the landing rollout I taxied to and stopped at the intersection of runway 17L where clearance to taxi is required to cross the runway. I did finally receive a flashing green light for taxi clearance from the tower at that time. I taxied back to my parking area without further incident.

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Original NASA ASRS Text

Title: A C172 PLT RPTS AN ELECTRICAL FAILURE AND A SUBSEQUENT LNDG AT A CLASS D ARPT WITHOUT A CLRNC VIA THE TWR CTLR'S LIGHT SIGNALS.

Narrative: WHILE TAKING A LCL VFR FLT IN CLR SKIES IN THE DENVER METROPOLITAN AREA, MY ACFT SUFFERED A COMPLETE ELECTRICAL SYS FAILURE. ALL SYS WERE LOST INCLUDING BOTH RADIOS, ADF, AND XPONDER. I DETECTED THE ONSET OF THE FAILURE BY NOTICING THE GRADUAL DIMMING OF THE RADIO FREQ DISPLAY LIGHTS. SHORTLY THEREAFTER, (IE, MINS) ALL ELECTRICAL SYS WENT DARK. AFTER AN ESTIMATED 5-10 MINS OF TROUBLESHOOTING ON MY PART, I DETERMINED THAT I WAS NOT GOING TO RESTORE PWR. I WOULD HAVE TO RETURN TO CENTENNIAL RPT FOR LNDG WITHOUT OBTAINING THE CURRENT ATIS INFO OR BEING IN RADIO CONTACT THE CTL TWR. I DID NOT INTEND TO OPERATE ON BATTERY PWR ANY LONGER THAN NECESSARY. I ENTERED THE CLASS D AIRSPACE IN AN AREA AND AT AN ALT TYPICAL OF ARPT TFC AND PROCEEDED TO APCH THE ARPT AREA. WHEN APPROX 2-3 MI FROM THE ARPT, I SIGNALED THE CTL TWR BY WAVING (IE, ROLLING) MY WINGS IN A FASHION DESIGNED TO INDICATE THAT MY ACFT HAD A PROB. AT THAT TIME I HAD THE CTL TWR IN CLR VIEW. I STUDIED THE TWR CAREFULLY FOR LIGHT SIGNALS BUT RECEIVED NONE. AFTER HAVING DETERMINED THAT THERE APPEARED TO BE NO ACFT IN THE TFC PATTERN FOR RWY 17R, I ENTERED THE RWY 17R PATTERN DOWNWIND MIDFIELD AT PATTERN ALT. DURING THE DOWNWIND PHASE I CONSTANTLY MONITORED THE TWR FOR SIGNALS BUT RECEIVED NONE. I CONTINUED WITH THE APCH, TURNED BASE AND FINAL WITHOUT ANY INDICATION OF LIGHT SIGNALS FROM THE CTL TWR. AT THAT POINT I COMMITTED THE ACFT FOR LNDG AND PROCEEDED TO LAND WITHOUT RECEIVING AN AUTHORIZING LIGHT SIGNAL. AT ANY GIVEN TIME, CENTENNIAL ARPT IS QUITE BUSY AND IT IS ESPECIALLY BUSY AT THAT TIME OF THE MORNING. IN MY JUDGEMENT, ALTHOUGH I HAD RECEIVED NEITHER CLRNC NOR DENIAL TO LAND, IT WAS SAFER FOR ME TO COMPLETE THE LNDG THAN TO GO AROUND AND WAIT FOR AN AUTHORIZING SIGNAL (WHICH I WAS UNSURE AS TO WHETHER I WOULD RECEIVE OR NOT). CONDITIONS AT THAT MOMENT WERE EXTREMELY FAVORABLE AS THERE WERE NO OTHER ACFT (THAT I COULD SEE) IN THE PATTERN OR ON THE GND IN THE IMMEDIATE VICINITY OF MY INTENDED RWY. AFTER COMPLETION OF THE LNDG ROLLOUT I TAXIED TO AND STOPPED AT THE INTXN OF RWY 17L WHERE CLRNC TO TAXI IS REQUIRED TO CROSS THE RWY. I DID FINALLY RECEIVE A FLASHING GREEN LIGHT FOR TAXI CLRNC FROM THE TWR AT THAT TIME. I TAXIED BACK TO MY PARKING AREA WITHOUT FURTHER INCIDENT.

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.