Narrative:

What started out as a training flight towards the instrument rating turned into an unplanned learning event on emergency procedures; IFR and VFR. The instrument student; a CFI friend of his as passenger; and I took off near sunset to practice basic attitude instrument flight procedures and introduction to instrument VOR tracking. About 1/2 hour into the flight; 2 things happened: the first was that the student or CFI passenger made a comment about whether the interior lights were getting dimmer. I looked at the ammeter (which is on the right side of the panel; in front of me); but somehow in the normally relatively dim red panel flood light; I misread the gauge. What was actually a discharge reading appeared to me to be a 'no charge/discharge' indication; which is how many ammeters read 'normal.' the second event was the student complaining about the glare from an unlabeled amber light located between the attitude indicator and the heading indicator. Initially he asked me if I had something to cover it; to reduce the glare. (I have seen this light on 2 previous flts; but the student was unsure as to its purpose. The aircraft belongs to a flying club to which the student belongs. It is an original model C172; and much modified from its original panel and equipment. Even though I have over 1500 hours in C172's in a variety of models dating from the mid 1960's to the mid 2000's; this airplane is actually still an unfamiliar aircraft to me. One anomaly is the unlabeled light mentioned above.) while I was looking for something to deal with the glare from the light; I asked whether anyone knew what the light indicated. I have asked on a previous flight; but the student was unsure. I believe the CFI passenger proffered that it might be a generator warning light. I continued to look at the visible exterior and interior light for any sign of dimming; as well as the ammeter; which I was still misinterping. (In hindsight; it was increasingly more difficult to read/interpretation due to the dimming light.) after a few mins; I was growing more uncomfortable with the possibility of an electrical failure at night; and suggested we start back towards the airport. I had the student begin to shed unnecessary electrical equipment (landing light) and tested the comrdos to see if we could still transmit. About this time; the #1 communication began to fade 'off' and 'on.' I also shined my flashlight on the ammeter; which I could now see was indicating a discharge of about 20 amps. I then had the student turn off the transponder and strobe to save what remaining batter power we could. While we returned to enter the traffic pattern at ZZZ; I made a 'blind' transmission on ZZZ tower frequency declaring an emergency; but received no response. I then tried to contact them via my cell phone; but was unable to establish cell service. I instructed both the student and CFI passenger to be extremely vigilant outside; because we were now essentially invisible to both radar and visual contact. As we entered the class D airspace from the west; another aircraft in closed left traffic to runway 1 at ZZZ was evident. We fell in behind that aircraft; made another attempt at a 'blind' transmission to the local controller; and continued to watch the tower cabin attendant for any sign of a light signal. Additionally; I had the student cycle the landing light switch several times while headed toward the tower; in the off chance they might see the light. (The light appeared to illuminate; but was apparently not seen by the tower). After the preceding aircraft made a touch-and-go; we landed on runway 1; rolled down to exit at taxiway K; squeezed past a piper waiting to depart at taxiway K; and stopped clear of that aircraft and the runway. I then tried; again (successfully; this time) to contact ZZZ tower on my cell phone. When they answered; I declared our emergency status; and gave a short account of our situation. They had not received either of our xmissions; and did not mention if they had seen our landing light signal. The controller did say they 'thought they had seen a ghost;' and then cleared us to our ramp area; which we were able to taxi to with a combination of local knowledge and externally held flashlight.(a relatively moonlit sky helped considerably!). After we were parked; I called tower again via cell phone to let them know we were completely clear. What I learned most from this event is that an aircraft can be 'unfamiliar' even with lots of experience in the same type. In retrospect; I should have relied less on the student's familiarity with 'his' aircraft; and reviewed the plane more before acting as PIC. The basic problem turned out to be a popped generator circuit breaker; mounted in a difficult-to-view location. Aircraft of this vintage have virtually nothing in the way of abnormal checklists/QRH's; and I'm guilty of 'assuming' the generator had simply died and couldn't be reactivated. A particular irony on this flight was the emphasis I placed during the preflight briefing on the need to monitor system (ammeter; oil; vacuum) instruments even more diligently than during VFR operations; in order to foresee an approaching problem before it reaches a critical level.

Related reports:

Google
 

Original NASA ASRS Text

Title: C172 INSTRUCTOR AND STUDENT REPORT GENERATOR FAILURE THAT GOES UNDIAGNOSED UNTIL THE BATTERY IS NEARLY DEPLETED. PILOTS RETURN FOR SUCCESSFUL NO LIGHT NO RADIO NIGHT LANDING. TRIPPED CIRCUIT BREAKER CAUSED THE PROBLEM.

Narrative: WHAT STARTED OUT AS A TRAINING FLT TOWARDS THE INST RATING TURNED INTO AN UNPLANNED LEARNING EVENT ON EMER PROCS; IFR AND VFR. THE INST STUDENT; A CFI FRIEND OF HIS AS PAX; AND I TOOK OFF NEAR SUNSET TO PRACTICE BASIC ATTITUDE INST FLT PROCS AND INTRODUCTION TO INST VOR TRACKING. ABOUT 1/2 HR INTO THE FLT; 2 THINGS HAPPENED: THE FIRST WAS THAT THE STUDENT OR CFI PAX MADE A COMMENT ABOUT WHETHER THE INTERIOR LIGHTS WERE GETTING DIMMER. I LOOKED AT THE AMMETER (WHICH IS ON THE R SIDE OF THE PANEL; IN FRONT OF ME); BUT SOMEHOW IN THE NORMALLY RELATIVELY DIM RED PANEL FLOOD LIGHT; I MISREAD THE GAUGE. WHAT WAS ACTUALLY A DISCHARGE READING APPEARED TO ME TO BE A 'NO CHARGE/DISCHARGE' INDICATION; WHICH IS HOW MANY AMMETERS READ 'NORMAL.' THE SECOND EVENT WAS THE STUDENT COMPLAINING ABOUT THE GLARE FROM AN UNLABELED AMBER LIGHT LOCATED BTWN THE ATTITUDE INDICATOR AND THE HDG INDICATOR. INITIALLY HE ASKED ME IF I HAD SOMETHING TO COVER IT; TO REDUCE THE GLARE. (I HAVE SEEN THIS LIGHT ON 2 PREVIOUS FLTS; BUT THE STUDENT WAS UNSURE AS TO ITS PURPOSE. THE ACFT BELONGS TO A FLYING CLUB TO WHICH THE STUDENT BELONGS. IT IS AN ORIGINAL MODEL C172; AND MUCH MODIFIED FROM ITS ORIGINAL PANEL AND EQUIP. EVEN THOUGH I HAVE OVER 1500 HRS IN C172'S IN A VARIETY OF MODELS DATING FROM THE MID 1960'S TO THE MID 2000'S; THIS AIRPLANE IS ACTUALLY STILL AN UNFAMILIAR ACFT TO ME. ONE ANOMALY IS THE UNLABELED LIGHT MENTIONED ABOVE.) WHILE I WAS LOOKING FOR SOMETHING TO DEAL WITH THE GLARE FROM THE LIGHT; I ASKED WHETHER ANYONE KNEW WHAT THE LIGHT INDICATED. I HAVE ASKED ON A PREVIOUS FLT; BUT THE STUDENT WAS UNSURE. I BELIEVE THE CFI PAX PROFFERED THAT IT MIGHT BE A GENERATOR WARNING LIGHT. I CONTINUED TO LOOK AT THE VISIBLE EXTERIOR AND INTERIOR LIGHT FOR ANY SIGN OF DIMMING; AS WELL AS THE AMMETER; WHICH I WAS STILL MISINTERPING. (IN HINDSIGHT; IT WAS INCREASINGLY MORE DIFFICULT TO READ/INTERP DUE TO THE DIMMING LIGHT.) AFTER A FEW MINS; I WAS GROWING MORE UNCOMFORTABLE WITH THE POSSIBILITY OF AN ELECTRICAL FAILURE AT NIGHT; AND SUGGESTED WE START BACK TOWARDS THE ARPT. I HAD THE STUDENT BEGIN TO SHED UNNECESSARY ELECTRICAL EQUIP (LNDG LIGHT) AND TESTED THE COMRDOS TO SEE IF WE COULD STILL XMIT. ABOUT THIS TIME; THE #1 COM BEGAN TO FADE 'OFF' AND 'ON.' I ALSO SHINED MY FLASHLIGHT ON THE AMMETER; WHICH I COULD NOW SEE WAS INDICATING A DISCHARGE OF ABOUT 20 AMPS. I THEN HAD THE STUDENT TURN OFF THE XPONDER AND STROBE TO SAVE WHAT REMAINING BATTER PWR WE COULD. WHILE WE RETURNED TO ENTER THE TFC PATTERN AT ZZZ; I MADE A 'BLIND' XMISSION ON ZZZ TWR FREQ DECLARING AN EMER; BUT RECEIVED NO RESPONSE. I THEN TRIED TO CONTACT THEM VIA MY CELL PHONE; BUT WAS UNABLE TO ESTABLISH CELL SVC. I INSTRUCTED BOTH THE STUDENT AND CFI PAX TO BE EXTREMELY VIGILANT OUTSIDE; BECAUSE WE WERE NOW ESSENTIALLY INVISIBLE TO BOTH RADAR AND VISUAL CONTACT. AS WE ENTERED THE CLASS D AIRSPACE FROM THE W; ANOTHER ACFT IN CLOSED L TFC TO RWY 1 AT ZZZ WAS EVIDENT. WE FELL IN BEHIND THAT ACFT; MADE ANOTHER ATTEMPT AT A 'BLIND' XMISSION TO THE LOCAL CTLR; AND CONTINUED TO WATCH THE TWR CAB FOR ANY SIGN OF A LIGHT SIGNAL. ADDITIONALLY; I HAD THE STUDENT CYCLE THE LNDG LIGHT SWITCH SEVERAL TIMES WHILE HEADED TOWARD THE TWR; IN THE OFF CHANCE THEY MIGHT SEE THE LIGHT. (THE LIGHT APPEARED TO ILLUMINATE; BUT WAS APPARENTLY NOT SEEN BY THE TWR). AFTER THE PRECEDING ACFT MADE A TOUCH-AND-GO; WE LANDED ON RWY 1; ROLLED DOWN TO EXIT AT TXWY K; SQUEEZED PAST A PIPER WAITING TO DEPART AT TXWY K; AND STOPPED CLEAR OF THAT ACFT AND THE RWY. I THEN TRIED; AGAIN (SUCCESSFULLY; THIS TIME) TO CONTACT ZZZ TWR ON MY CELL PHONE. WHEN THEY ANSWERED; I DECLARED OUR EMER STATUS; AND GAVE A SHORT ACCOUNT OF OUR SITUATION. THEY HAD NOT RECEIVED EITHER OF OUR XMISSIONS; AND DID NOT MENTION IF THEY HAD SEEN OUR LNDG LIGHT SIGNAL. THE CTLR DID SAY THEY 'THOUGHT THEY HAD SEEN A GHOST;' AND THEN CLRED US TO OUR RAMP AREA; WHICH WE WERE ABLE TO TAXI TO WITH A COMBINATION OF LOCAL KNOWLEDGE AND EXTERNALLY HELD FLASHLIGHT.(A RELATIVELY MOONLIT SKY HELPED CONSIDERABLY!). AFTER WE WERE PARKED; I CALLED TWR AGAIN VIA CELL PHONE TO LET THEM KNOW WE WERE COMPLETELY CLEAR. WHAT I LEARNED MOST FROM THIS EVENT IS THAT AN ACFT CAN BE 'UNFAMILIAR' EVEN WITH LOTS OF EXPERIENCE IN THE SAME TYPE. IN RETROSPECT; I SHOULD HAVE RELIED LESS ON THE STUDENT'S FAMILIARITY WITH 'HIS' ACFT; AND REVIEWED THE PLANE MORE BEFORE ACTING AS PIC. THE BASIC PROB TURNED OUT TO BE A POPPED GENERATOR CIRCUIT BREAKER; MOUNTED IN A DIFFICULT-TO-VIEW LOCATION. ACFT OF THIS VINTAGE HAVE VIRTUALLY NOTHING IN THE WAY OF ABNORMAL CHKLISTS/QRH'S; AND I'M GUILTY OF 'ASSUMING' THE GENERATOR HAD SIMPLY DIED AND COULDN'T BE REACTIVATED. A PARTICULAR IRONY ON THIS FLT WAS THE EMPHASIS I PLACED DURING THE PREFLT BRIEFING ON THE NEED TO MONITOR SYSTEM (AMMETER; OIL; VACUUM) INSTS EVEN MORE DILIGENTLY THAN DURING VFR OPS; IN ORDER TO FORESEE AN APCHING PROB BEFORE IT REACHES A CRITICAL LEVEL.

Data retrieved from NASA's ASRS site as of May 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.