Should I touch that circuit breaker?

Have you ever looked carefully at the emergency and abnormal procedures in your operator’s handbook? Did you notice that the procedures often ask you to locate circuit breakers as part of the checklist?

CB panel in Cessna
Can you locate the important breakers without looking?

Checklists are great, but consider this: can you locate all of the circuit breakers mentioned in the procedures in less than five seconds?

Why not? It’s a bad idea to hunt for circuit breakers during an abnormal situation.

Every pilot should know the location of important circuit breakers, so here’s your homework:

  1. Go through all of the emergency and abnormal procedures in your operating handbook carefully. Write down every single CB mentioned in the procedures.
  2. Take that list of CBs to your aircraft and spend five minutes locating every single one of them.
  3. Spend another five minutes locating them with your eyes closed to mimic smoke and a dark cockpit.
  4. Do this every other time you fly until you can confidently locate all of them. Refresh every six months.

Tip: In our OH-58D, we would locate the CBs in relation to the corner of the CB panel. For example: “Hydraulics is 4 up and 3 over.” Use this tip to remember your important circuit breakers. At night and under night vision goggles, this method was a life saver. I could locate any important CB by feel since I would be at risk for spatial disorientation if I looked up for an extended period of time while the aircraft turned.

I want to mention one more thing with respect to circuit breakers: before you run out thinking you can pull circuit breakers, you should understand there are some general rules to pulling circuit breakers (regardless of the aircraft).

  1. You may push a popped circuit breaker back in once but…
  2. Never push a CB back in a second time. You are asking for an electrical fire!
  3. If you push a CB back in even once, be wary of an electrical fire and possible smoke in the cockpit.
  4. Some pilots will never push a circuit breaker back in if it’s above 10 amps. Think about it: if something was serious enough to pop a CB above 10 amps, are you sure you want to recreate the situation?
  5. If you are unsure, never touch a circuit breaker unless the emergency and abnormal checklist call for it.

Talk to your instructor about pushing in circuit breakers. There are some instances, like night IMC, where you may seriously consider touching even a high amp circuit breaker.

Most of the time it’s a good idea just to leave it popped. Some pilots never touch CBs. This isn’t a black and white issue, though, so spend some quality time staring at your circuit breaker panel imaging scenarios where you may or may not push circuit breakers. As always, your operator’s manual is king.

Any experiences or thoughts on circuit breakers? Leave a comment below so we can learn from each other.

9 Comments

  • All good food for thought.

    I am of the “don’t touch ’em persuasion”. In fact, I tend to think that airplanes should be designed so pilot’s can’t get at them except for the few breakers that may need to be pulled for a non-fire situation (like an autopilot runaway). Modern airplanes have enough electrical backup for orientation and navigation that just shutting the system down at the first sign of smoke should not be that big a deal. Troubleshooting in the air has proven, numerous times, to be a bad idea.

  • Word of experienced.
    One, popped CB is followed by some warning or flag. If youre trained properly, you know wheater to reset, or not.
    Two, popped CB with no indication, don’t touch. Go to Abnormal check list.
    Three, popped CB in group that supports ground/flight mode respectively, calls for excessive caution. Resseting in half the cases have no effect.

  • Hmmm…yes and no. The standard procedure for the last 20 years or so in the airline world is that a popped CB may be reset one time BUT only if necessary for the safety of flight. The second reset is, as you pointed out, absolutely verboten. Several CBs are prohibited from being reset in any circumstance…most notably fuel pump CBs.

    I have to express some skepticism at the risk management profile of memorizing CB locations, at least in the civilian world. Get familiar with them, most certainly. Memorizing by feel…maybe not. Of all the manufacturer procedures that call for pulling and resetting a CB, how many are absolutely necessary for the safety of flight? Now, compare that risk profile against the risk of inadvertantly pulling the wrong breaker. There may be some circumstances in which the former outweights the latter, but my guess is that most of the time, you could be exposing yourself to more risk, by pulling an incorrect CB based on feel, than the original risk warrants.

    The pitch trim CBs on the MD80 are one such critical set of breakers. They have to be accessed extremely quickly in certain cases of a runaway stabilizer. Typically, they are painted with nail polish or flat white paint. Although I’m not familiar with any GA airplanes these days, I have to believe that a similar technique would work for the very small number of CBs that are really that critical.

  • Most light aircraft circuit breakers are of the inexpensive ( ! ) but primative thermal type. Thus, after they trip, they typically require a cool-down interval before they will exhibit “normal” behavior. A hasty reset rarely will endure.

  • It’s not a bad idea to verify that all the CB’s can be pulled out. Sometimes they go bad or get difficult to pull. If that’s the case, they may not pop as advertised. Just a thought

  • The number & types of CB’s popped can also be a troubleshooting aid. With one engine of a DC-9 in serious trouble, the 6 popped CB’s helped us realize the problem was a burst engine accessory air duct that sliced through a cable bundle. Allowed us to keep the engine at idle, and not shut it down on a dark night, until we were back on the ground.

  • Eric:
    FYI, even the primative thermal breakers are required to be “trip free.” That means that even if the button cannot pop out – or is prevented from popping out, as by an insistent pilot – the breaker trip mechanism inside the housing still does its job. But you have no VISUAL indication of the tripped condition.

  • I like the “only push it in, even once, if necessary for flight safety”; I had collars around a few typically critical ones for tactile identification.

    Keep the good stuff coming!!

  • This is not directly related to this topic, but a few years ago at Oshkosh, I heard a talk given by an FAA maintenance inspector. He said the FAA had done tests on circuit breakers in older airplanes. They found that they popped at significantly higher amp values than they were rated for. However, they also found that if they were pulled & reset a few times they would pop considerably closer to their rated amperage. So it is probably a good idea, if you CBs that can be pulled, to pull all your breakers & reset them once in while when the airplane is on the ground with the power shut off,

Leave a Reply

Your email address will not be published. Required fields are marked *