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Lesson Learned: Circuit Breaker Pops Times Three!

By Eric McCarthy

After months of delays following an annual and the installation of new avionics, my friend Rich’s beloved and meticulously maintained 1985 C-172P was finally ready to fly again. I had one of my photo missions due and Rich graciously offered to fly with me out to the Imperial Valley to shoot the site. The flight would also serve as a shake-down run, an opportunity to put the new hardware to the test, and we were both anxious to get back in the saddle and ‘slip the surely bonds.’

The plane was in its usual spot at Palomar (KCRQ) and by the time I got there, Rich had already preflighted it and was patiently awaiting my arrival. I had left early but traffic on the 5 had conspired to make me late – not just a few minutes late, but a half hour late! I’ve tried many times, unsuccessfully, to beat Rich to the plane, but I failed miserably that morning… In fairness, he does have a 30-mile head start on me – he lives in town and I live 35 miles north – but still, I felt bad. 

I bring this up because my anxiety and frustration over being late may have affected my mental state as we prepared to depart. I didn’t feel ‘under pressure’ at the time, but subtle little things like this can add up.

Rich and I usually trade off flying PIC to and from my photo sites. Since it’s way easier and more comfortable to shoot out of the left side of the plane, and we planned to take the photos before refueling at Imperial (KIPL), I would be the PIC for the first leg. This would also provide an opportunity for Rich to try out his new equipment.

Preflight complete, we proceeded through the checklist to engine start: a couple of shots of prime, master on, “Clear prop!”ignition: start – the engine responded with a smooth start and settled nicely into its idle. With the engine idling, I checked the oil pressure, and flipped on the Avionics Master, but Rich immediately noticed and called out the low voltage warning light; I looked down and saw that the “ALT FLD” circuit breaker had ‘popped’ and attempted to reset it. This was my first experience in almost 40 years of flying, with a circuit breaker popping – I wasn’t really sure what to expect when I reached to reset it, but I wasn’t expecting the limp breaker button I got – I guess I thought it to be like the plunger on a ball-point pen, firmly held in position whether in or out. Well, it wasn’t going to reset, so we shut down. We hopped out and made a quick check of the v-belt that drives the alternator, checked for smoke and any other noticeable problems; all seemed in order. 

Back in the cockpit, with the master off, I reset the circuit breaker and, again following the checklist, we started the engine. Again, the low voltage light illuminated and the “ALT FLD” circuit breaker popped… Hmmm, that’s odd… Well, let’s give it one more try… Again, the circuit breaker popped; we shut down.

Hmmm…well, the plane did just come out of the shop; maybe something got disconnected or misconnected during all the installation commotion… Rich called his mechanic, described what we were experiencing and asked if he would take a quick look. 

“Sure – bring it by…”

Getting the plane to the mechanic would involve a short hop to Fallbrook Air Park (L18), a small, uncontrolled airport about 15 miles north of Palomar, but at least now we had a plan: get a quick fix, then onward and upward! 

We knew that if the circuit breaker popped again before we departed or on the way to L18, the battery should last the 20 minutes it would take to get there. And if it didn’t, the Garmin G5’s and the Aera GPS each have their own internal batteries, so they’d still work and besides, it was a nice VFR day. The only potential problems would be that we’d have no radios and no flaps. The lack of radios didn’t really concern us – Fallbrook’s an uncontrolled field usually hosting light traffic. We should be able to join the traffic pattern with minimal fuss.

The lack of flaps was more of a concern: landing on the USS Fallbrookwith its 2,160-foot runway could be a challenge – overruns at L18 have claimed planes flown by better pilots – but a 172 in a flat-out dive doesn’t go all thatfast, so as long as we planned for a no-flaps landing and came over the fence between 65 - 70 knots, we should be able to stop in the allotted space.

We started up and, wouldn’t you know it – now that we had an appointment with a mechanic – the circuit breaker didn’t pop! Still, we shed all extra load: no lights, Nav/Comm 2 and the DME off, and we even unplugged the Stratus in the back seat. We were wondering how the circuit breaker would hold up through the run up, but it held just fine. We departed and flew a completely uneventful flight to L18. Guess it was just an intermittent problem…maybe something loose?

The mechanic removed the cowling, brought out his multimeter, and ran through some tests. He chased down some wiring, checked to make sure the connections were secure, and found some ‘weakness’ in the alternator but nothing conclusive, so he moved to the next step and removed the alternator for further examination. This revealed a loose stud that could have been causing a fault – this was encouraging and supported our notion of something loose causing an intermittent problem. He tightened the stud, ran through some more testing, reinstalled the alternator and determined that all was good. Cleared for takeoff!

We departed L18, dodging clouds as we climbed to clear the 5,600-foot ridgeline at Julian VOR (JLI). It was pretty gusty as we left Fallbrook so we climbed to 9,500-feet seeking smoother air on top of the clouds and to put some extra altitude between us and the mountains. Downdrafts on the lee side of a ridge can be detrimental to your health…

As expected, the clouds evaporated as we entered the desert on the other side of the ridge, but it was still pretty breezy as we descended to the photo site. We completed the photo mission and headed to Imperial (KIPL) to refuel. As is often the case at Imperial, it was hot and the wind was blowing pretty strong – 21, gusting to 34 knots – but fortunately right down runway 21. I caught it just right and greased one on – lucky!

Refueled, we were ready for the one hour flight back to the coast. Rich flew the return leg; because of all the delays getting out to Imperial, we half expected that the clouds would have filled in as the marine layer crept back onshore, but that didn’t happen and Rich was able to complete the flight VFR with a nice landing of his own. 

All of this without any further problems with the circuit breaker. So I guess we solved the problem, right?

The next day I got a text from Rich; he had planned some recurrent training with his instructor – and the same thing happened again! Three times the ‘ALT FLD’ circuit breaker popped! This time the mechanic recommended a new alternator, a new alternator control unit, and a new circuit breaker.

This got me thinking: had we made a bad choice in flying the plane to Fallbrook that day? Had we taken an unwarranted and unacceptable risk?

I began to analyze the situation, circumstances, and our thought processes. I began by looking at what we knew: the circuit breaker had popped; the ammeter showed a discharge (as expected); there was no smoke or any other telltales that might indicate imminent danger; the avionics were working – and would continue to work even if the circuit breaker popped; the battery should last the 20 minutes it would take us to fly to Fallbrook – especially since we had reduced the load by shutting off redundant and unnecessary equipment; and the mechanic had said he’d take a look at it. 

Then I began to examine what I thought might be some of our subconscious thoughts: Rich and I have flown quite a bit with each other over the past few years, and we respect each other’s skill and judgment as pilots. I know Rich to be a good pilot; he’s smart and safety-oriented, and hey – it’s his plane! I’ll put some words in Rich’s mouth: he knows I’ve been flying for a long time and I’m a pretty good pilot; he also knows I’m generally risk-averse – he’s seen me cancel mid-flight to spend the night away from home rather than blunder into worsening conditions; and, I was PIC for this leg. Both of us wanted to complete the mission; and, again, the mechanic had said he’s take a look at it – no dire warnings – “Step away slowly…”or “Run! She’s gonna blow!” or anything like that. That was reassuring and it seemed reasonable at the time that we should make the flight.

But the fact that I’m even thinking about this now tells me that I probably should have thought more about it then… 

Three items really stood out to me: 

• From my perspective: “It’s his plane”– in other words, he knows his plane – if Rich says it’s ok, it’s ok!

• From what I perceived to be Rich’s perspective: “Eric’s PIC”– or, if he says it’s ok, it’s ok!

• And for both of us: the mission-mindset– a trait I think we share with almost every other pilot – we wanted to fly and complete the mission at hand.

None of these were conscious thoughts, but rather subtle, subconscious proddings. Add to this the fact that I was late arriving and anxious not to disappoint any further and you begin to see some causal factors that may have influenced my/our thought processes. 

I put all of this into a safety briefing for my Civil Air Patrol squadron, hoping to learn from a room full of experience. We’ve got former and active military pilots, airline pilots, and experienced GA pilots in our squadron, as well as several guys with significant maintenance experience, both in the military and in CAP. In short: plenty of experience I could draw on. 

So I posed the question: had we taken an unnecessary risk?

The sobering response came quickly from a man with more flight time than I’ll ever have, more experience in the maintenance shack, and who I deeply respect: “Why would you even try to reset the circuit breaker three times? In the airlines we got one attempt to reset – then the plane is grounded. You don’t know what’s going on electrically – the plane could catch fire in flight!”

Yikes! I hadn’t even considered that! I just assumed that the alternator had failed; maybe it had, or maybe there was a fault in the wiring from the alternator; maybe it was shorting through a chafed wire near a fuel line – I had no idea…but this was an eye-opening revelation to me. 

Nobody likes to be exposed for making a bad decision, even though I’d asked for it by presenting it to the squadron. I imagine I’ll get further feedback from some of you when you read this. I’m okay with that – in fact, I look forward to learning from others so I can make better, more informed decisions in the future, just as I hope others will learn from my experiences. We assume risk every time we mount up in our aerial steeds, but we also try to minimize risk wherever possible. One way to do that is to continue to learn about our chosen avocation. Everything worked out fine – this time. But it might not have…

That’s all for now; until next time – fly safe!


Editor’s Note: Letters to the Editor are welcomed. Email to vickie@inflightusa.comor mail to P.O. Box 5402, San Mateo, CA 94402.


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