“Deactivating” inop equipment - circuit breaker operation

[CerroTorre]

Ran into a question I couldn’t fully resolve recently. It’s a little pedantic and maybe the result of some over thinking but …

For example, an inop landing light can be flown legally in day VFR but still requires deactivation first. This question arose because the aircraft in question had the type of circuit breaker that is the “push to reset” type and not (to my limited knowledge) “pullable” in order to open the circuit. Holding them in did not “pop” them out.

Since “deactivation” requires making the equipment “unusable to the pilot or crew” one can’t simply fly while leaving the switch in the off position and call that “deactivated” (I know - dumb point but it came up), so how would one do an in-the-field deactivation to allow a legal flight home?

 

[CerroTorre]

Second question, why are these types of circuit breakers used? Or, more likely, what am I missing in my understanding of how they work?

 

[Bell206]

Since “deactivation” requires making the equipment “unusable to the pilot or crew” one can’t simply fly while leaving the switch in the off position and call that “deactivated”

There was FAA guidance at one time that stated this exact thing. Turning the switch off and placarding the switch per Part 91.213(d) meets the intent. There have been many discussions on this but its boils down to what you choose to do and how you sign it off.

why are these types of circuit breakers used?

They cost less than the other types.

 

[CerroTorre]

Copy. So a grey area that, by necessity involves some discretion on the part of the pilot depending on the particulars of the equipment involved and the failure mode/cause. i.e. use good judgement, don’t be a dummy, and follow the rules. And hope you don’t get unlucky with an overly uptight ramp inspection.

Seems appropriate although mildly, annoyingly ambiguous. But tolerable. Like a lot of regs.

I’d be interested to read the FAA guidance on this if anyone has the reference.

“They cost less” - makes sense.

Thanks for the reply Bell206

 

[Bell206]

I’d be interested to read the FAA guidance on this if anyone has the reference.

The go to reference was AC 91-67 which was cancelled. A copy is linked below. The cancellation notice stated the AC was no longer aligned with ICAO guidance so they cancelled it. Still haven't been able to find out what was "misaligned".
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-67.pdf

 

[Half Fast]

There was FAA guidance at one time that stated this exact thing. Turning the switch off and placarding the switch per Part 91.213(d) meets the intent. There have been many discussions on this but its boils down to what you choose to do and how you sign it off.

In my Beech, some of the switches are also the breakers, similar to this part: https://www.aircraftspruce.com/cata...MIg6Sis9zq-gIVSIlaBR09yA9eEAQYASABEgLSyfD_BwE . In fact, my landing light is an example. So when I turn off the switch, I've "pulled" the breaker.

When a landing light is burned out, hasn't it self-deactivated?

 

[asicer]

In my Beech, some of the switches are also the breakers, similar to this part: https://www.aircraftspruce.com/cata...MIg6Sis9zq-gIVSIlaBR09yA9eEAQYASABEgLSyfD_BwE . In fact, my landing light is an example. So when I turn off the switch, I've "pulled" the breaker.

The restart six-pack 172/182's have those on all the lights, pitot heat and fuel pump. Are yours like that the from the factory?

 

[3393RP]

First use a Sharpie and write "DNFW" on a piece of duct tape. Then place the tape on the landing light switch.

You're good.

Edit: NFG works too.

 

[Half Fast]

The restart six-pack 172/182's have those on all the lights, pitot heat and fuel pump. Are yours like that the from the factory?

Yes, AFAIK, but the plane is 53 years old.

 

[Bell206]

When a landing light is burned out, hasn't it self-deactivated?

Possibly, provided the bulb has been verified burnt. But if the landing light is out due to a short in the wire then its not really deactivated which could lead to other issues or "hazards" as indicated in 91.213.

 

[pfarber]

Tripping a breaker is usually the most convenient, but not the only way to deactivate an item. Problem is most other ways require an MX to isolate.

For a light, simply remove the bad bulb. The circuit is open and will not conduct.

The FAR does not state that a circuit must be de-energized as a breaker may have other working items on it that you can still use.

 

[Maxnr]

How about a log book entry in addition to labeling it afu. Must have if the aircraft has a Minimum Equipment List.

 

[Bell206]

How about a log book entry in addition to labeling it afu. Must have if the aircraft has a Minimum Equipment List.

FYI: 91.213(d) states if any maintenance is required to deactivate equipment and entry must be made in the logbook per Part 43 regardless if it has an MEL or any other listing.

 

[SoonerAviator]

Tripping a breaker is usually the most convenient, but not the only way to deactivate an item. Problem is most other ways require an MX to isolate.

For a light, simply remove the bad bulb. The circuit is open and will not conduct.

The FAR does not state that a circuit must be de-energized as a breaker may have other working items on it that you can still use.

Unless the short in the circuit was prior to the light bulb base . . .