Don't reset that breaker?

[Wankel7]

Just wondering what some of the thoughts were on this article?

I would normally wait a minute or two after one pops to attempt a reset. However, its no longer recommended to even do that?

http://findarticles.com/p/articles/mi_m0UBT/is_9_14/ai_59816783

 

[avbug]

Resetting breakers multiple times is generally always a bad idea. Some pilots treat breaker openings as nothin, others use breakers as a switch. Invariably all seem to forget or misunderstand that the circuit breaker has only one purpose, and that is to protect the circuit wiring. It isn't there as a safety valve for equipment, it isn't even there to protect the equipent. It's there to protet the wiring, which is the weakest and quickest to heat part of the circuit in the event of a short.

Conventional wisdom lies in resetting the circuit breaker once. However, this my not always be advisable. There is no substitute for knowing the system, EXCEPT for following proceedure. Unless the published proceedure calls for resetting the circuit breaker, it should probably be left alone...and whereas most all proceeures don't allow for resetting the breaker more than once, one should stick closely to the poceedure and not experiment.

When you reset that breaker, especially if it's opened because of a feeder fault or short, you may be suddenly powering something entirely different than what you think is powered through or attached to that breaker. In fact, the circuit may be rerouted now due to the short, and you may be causing an entirely different set of problems.

When a breaker opens, referrence the appropriate checklist. Pilot discretion is always applicable, but in absence of an emergency or dire need, one should yield to the published proceedures and defer to those before striking out on one's own.


Some of the most dangerous arcing doesn't necessarily trip a breaker...it may result in arcing to another circuit in wire bundle which trips an entirely different breaker...resetting that breaker may result in fire, or re-energize a circuit that has been opened, and resupply the fire site with an ignition source.

As an example: On January 18, 1990, a US Air MD-80, en route to Cleveland from Buffalo, was forced to return to Buffalo when the cockpit filled with smoke from overheated electrical wire insulation. The left generator tripped off-line and the captain turned the right generator control switch to the "Off' position. He selected emergency power and initially was able to clear the smoke. The captain then started the auxiliary power unit (APU) and the cockpit again started to fill with smoke. The A.P.U. electrical power was then shut off and the emergency electrical power was turned back on. The aircraft returned to Buffalo with no further reports of smoke. It was found that the left generator phase B power feeder cable terminal, which is connected to a plastic terminal strip, had melted from intense arcing . The terminal, approximately, 15 inches of the cable, and the terminal stud had melted. The second source of smoke came from a fire started by the molten metal that sprayed an area forward of, and below the terminal strip. The only circuit breaker to trip was the cabin temperature control.

In another case, On November 24,1993, a MD-87 experienced smoke and a subsequent fire upon touchdown. The fire damage was severe, including a 1-foot-diameter hole in the skin. Investigation found that two wires, one 115 volts (V) and one 29V, had been pinched together and were arcing to the fuselage structures. Neither the 10-ampere (amp) circuit breaker (28V line) nor the 15-amp circuit breaker (115V line) tripped. This is a case of a breaker failing to open. However, had one of the breakers oened the source of the fire *may* have ceased...had the pilot reset it, and it probably would have stayed reset, the fire would have been restarted...or at least the ignition source re-energized. Serious stuff.

A couple of years prior to this, on March 17,1991,a Delta L-1011 en route from Frankfurt, Germany, to Atlanta, Georgia, was forced to make an unscheduled landing in Goose Bay, Labrador, Canada. About 7.5 hours into the flight, flames erupted from the base of the left cabin sidewall panel to the height of the seatback tray at the next to last row of passenger seats. The fire was extinguished and a precautionary landing was made. The ignition source of this fire was not determined; however, a possible source of ignition appeared to be an electrical fault. Some of the wires in a fifteen wire bundle located in the fire area exhibited evidence of arcing. Five circuit breakers connected to this wire bundle had tripped. Addressing only these breakers may have missed the point entirely, as the open breakers were a result of the fire...not feeder faults associated with their particular circuit functions. Resetting the breaker would have restored power to the circuit, or the shorted circuit, at the fire site.

 

[Coool Hand Luke]

Nice post.

 

[Wankel7]

Outstanding post Avbug! Thank you ... that was very informative

Here is a link to the Advisory Circular that talks about the FAA change feelings on resetting a breaker.

http://www.airweb.faa.gov/Regulator...681e9d8c5e86256e4a00744607/$FILE/AC120-80.pdf

 

[kingaira90]

Great info. It is company policy to not reset breakers in flight unless there is a published procedure. Nice to see more info on why that is a good idea. -kingaira90

 

[kirk]

Just wondering what some of the thoughts were on this article?

I would normally wait a minute or two after one pops to attempt a reset. However, its no longer recommended to even do that?

http://findarticles.com/p/articles/mi_m0UBT/is_9_14/ai_59816783

I just hope differentiation is maintained between a popped CB and a need to recycle one because a locked up gadget has no other ON/OFF switch installed.

 

[avbug]

Unless the published proceedure calls for it, opening a circuit breaker isn't a good idea (especially in flight), even for a "locked up gadget."

A ciruit breaker isn't a switch, at least not in the conventional sense of an operational switch for intentionally turning something on or off, or four routine interruptions in power supply. It's a protective device, only.

If a gadget has locked up, discovering the cause is probably more important than "unlocking" it. Discovering the cause is an endevor best done on the ground.

 

[B6 Tech]

Resetting breakers multiple times is generally always a bad idea. Some pilots treat breaker openings as nothin, others use breakers as a switch. Invariably all seem to forget or misunderstand that the circuit breaker has only one purpose, and that is to protect the circuit wiring. It isn't there as a safety valve for equipment, it isn't even there to protect the equipent. It's there to protet the wiring, which is the weakest and quickest to heat part of the circuit in the event of a short.

Conventional wisdom lies in resetting the circuit breaker once. However, this my not always be advisable. There is no substitute for knowing the system, EXCEPT for following proceedure. Unless the published proceedure calls for resetting the circuit breaker, it should probably be left alone...and whereas most all proceeures don't allow for resetting the breaker more than once, one should stick closely to the poceedure and not experiment.

When you reset that breaker, especially if it's opened because of a feeder fault or short, you may be suddenly powering something entirely different than what you think is powered through or attached to that breaker. In fact, the circuit may be rerouted now due to the short, and you may be causing an entirely different set of problems.

When a breaker opens, referrence the appropriate checklist. Pilot discretion is always applicable, but in absence of an emergency or dire need, one should yield to the published proceedures and defer to those before striking out on one's own.


Some of the most dangerous arcing doesn't necessarily trip a breaker...it may result in arcing to another circuit in wire bundle which trips an entirely different breaker...resetting that breaker may result in fire, or re-energize a circuit that has been opened, and resupply the fire site with an ignition source.

As an example: On January 18, 1990, a US Air MD-80, en route to Cleveland from Buffalo, was forced to return to Buffalo when the cockpit filled with smoke from overheated electrical wire insulation. The left generator tripped off-line and the captain turned the right generator control switch to the "Off' position. He selected emergency power and initially was able to clear the smoke. The captain then started the auxiliary power unit (APU) and the cockpit again started to fill with smoke. The A.P.U. electrical power was then shut off and the emergency electrical power was turned back on. The aircraft returned to Buffalo with no further reports of smoke. It was found that the left generator phase B power feeder cable terminal, which is connected to a plastic terminal strip, had melted from intense arcing . The terminal, approximately, 15 inches of the cable, and the terminal stud had melted. The second source of smoke came from a fire started by the molten metal that sprayed an area forward of, and below the terminal strip. The only circuit breaker to trip was the cabin temperature control.

In another case, On November 24,1993, a MD-87 experienced smoke and a subsequent fire upon touchdown. The fire damage was severe, including a 1-foot-diameter hole in the skin. Investigation found that two wires, one 115 volts (V) and one 29V, had been pinched together and were arcing to the fuselage structures. Neither the 10-ampere (amp) circuit breaker (28V line) nor the 15-amp circuit breaker (115V line) tripped. This is a case of a breaker failing to open. However, had one of the breakers oened the source of the fire *may* have ceased...had the pilot reset it, and it probably would have stayed reset, the fire would have been restarted...or at least the ignition source re-energized. Serious stuff.

A couple of years prior to this, on March 17,1991,a Delta L-1011 en route from Frankfurt, Germany, to Atlanta, Georgia, was forced to make an unscheduled landing in Goose Bay, Labrador, Canada. About 7.5 hours into the flight, flames erupted from the base of the left cabin sidewall panel to the height of the seatback tray at the next to last row of passenger seats. The fire was extinguished and a precautionary landing was made. The ignition source of this fire was not determined; however, a possible source of ignition appeared to be an electrical fault. Some of the wires in a fifteen wire bundle located in the fire area exhibited evidence of arcing. Five circuit breakers connected to this wire bundle had tripped. Addressing only these breakers may have missed the point entirely, as the open breakers were a result of the fire...not feeder faults associated with their particular circuit functions. Resetting the breaker would have restored power to the circuit, or the shorted circuit, at the fire site.

What online mag di you copy and paste that from? You should give credit to its true author.

 

[avbug]

Those are my statements, take them or leave them. What exactly is your problem?

The three example accounts I obtained in part from some discussion on aging aircraft wiring, and included my own comments.

 

[AngelKing]

B6, that is one of his shorter post.

AK