Looking for design reference on aircraft circuit breakers 2

[kontiki99]

I'm looking for and circuit breaker protection for aircraft power distribution systems. Anyone know where I should be looking?

In theory, there is no difference between theory and practice however, experience suggests that in practice, there is!

My posts reflect my personal views and are not in any way endorsed or approved by any organization I'm affiliated with.

 

[WKTaylor]

Kontiki99

Circuit breakers are a necessary pain. When they need to work is when they are absolutely a life saver... however...

They age and deteriorate, corrode internally, fatigue [springs, pins, plastic, etc] and need constant maintenance such as visual isnspection for signs of overheating and manual breaking/popping and resetting to clean-off any arc-flash welds or corrosion between contact surfaces, etc [an make sure they work "ok" to the touch.

They SHOULD be tested every few years on a CB tester [used to verify that breakers function as planned under high stress circuit loads].

Most convential breakers under typical loads can last 15+/- years... however, if Mods are added and/or wiring loads increase, they may fail dramatically sooner [IE: a high current electric motor starts to sieze, etc]. This only gets worse in a extremely corrosive [sea coast] atmosphere.

OH yeah a single failed breaker in the middle of a panel can over-heat/burn and spread the damage through-out the adjacent breakers on the panel.

Typical CB related data/info [not specific CB specs] is as follows...

NOTE: Circuit breakers are technically an "electric overcurrent protective device".

NOTE: within these specs are references to many other useful/relevant specs/data, etc.

FAA AC25.13567-1 Circuit protective devices

FAA AC25-16 Electrical Fault and Fire Prevention and Protection

FAA AC43-206 Inspection, Prevention, Control, and Repair of Corrosion on Avionics Equipment

SAE ARP1199, DEVICES, ELECTRIC OVERCURRENT PROTECTIVE, SELECTION, APPLICATION, AND INSPECTION OF

SAE ARP4101/5 Aircraft Circuit Breaker and Fuse Arrangement

SAE ARP4404 Aircraft Electrical Installations

SAE AS50881 WIRING, AEROSPACE VEHICLE

SAE AS58091 Circuit Breakers, Trip-Free, Aircraft General Specification For

SAE J553 Circuit Breakers

SAE/TP 2006-01-2419 Arc Fault Protection, Application Techniques for Aircraft Circuit Breakers

MIL-DTL-27715 CIRCUIT BREAKER, TRIP-FREE, HIGH TEMPERATURE, AIRCRAFT GENERAL SPECIFICATION FOR

MIL-DTL-23928 PANELS, ELECTRICAL, POWER DISTRIBUTION AND MANUAL TRANSFER, CIRCUIT BREAKER TYPE

MIL-HDBK-522 GUIDELINES FOR INSPECTION OF AIRCRAFT ELECTRICAL WIRING INTERCONNECT SYSTEMS

MIL-HDBK-5400 ELECTRONIC EQUIPMENT, AIRBORNE GENERAL GUIDELINES FOR

MIL-STD-7080 SELECTION AND INSTALLATION OF AIRCRAFT ELECTRIC EQUIPMENT

WRDC-TR-90-4075 FAILURE ANALYSIS TECHNIQUES FOR THE EVALUATION OF ELECTRICAL AND ELECTRONIC COMPONENTS IN AIRCRAFT ACCIDENT INVESTIGATIONS

WL-TR-95-4004 AIRCRAFT MISHAP INVESTIGATION HANDBOOK FOR ELECTRONIC HARDWARE

DOT/FAA/AR-01/118 Aircraft Age-Related Degradation Study on Single- and Three-Phase Circuit Breakers

USAF T.O. 1-1-686-1, CLEANING AND CORROSION CONTROL VOLUME I CORROSION PROGRAM AND CORROSION THEORY
USAF T.O. 1-1-686-3, CLEANING AND CORROSION CONTROL VOLUME III AVIONICS AND ELECTRONICS
USAF T.O. 1-1-686-5, CLEANING AND CORROSION CONTROL VOLUME V CONSUMABLE MATERIALS AND EQUIPMENT FOR AVIONICS

USAF T.O. 1-1A-14 INSTALLATION AND REPAIR PRACTICES VOLUME 1 AIRCRAFT ELECTRIC AND ELECTRONIC WIRING

Etc... Gotta go back to work...



Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[kontiki99]

Thanks Wil,

I've been trying to better understand intermittent and one off trip problems on in service aircraft (large and small). The urgency is behind me, but its a subject that doesn't go away. Maybe the answer is a maintenance program. It's naive to expect a device with seldom exercised electrical contacts can be ignored forever.

In theory, there is no difference between theory and practice however, experience suggests that in practice, there is!

My posts reflect my personal views and are not in any way endorsed or approved by any organization I'm affiliated with.

 

[WKTaylor]

K99...

You are correct sir.

Reason I beacame so versed on CBs is that airborne CB [panel] fires are dangerous and messy; and CBs have a surprising number of fault/failure modes which cause all sorts of electrical system maintenance grief.

We discovered that a maintenance program that deliberately cycles each circuit breaker in an aircraft [and in MiL acft there can be +200, here/there, accessible/nonaccessible, various 'sizes' and types] makes a huge difference in minimizing electrical problems... and identifying CB deterioration early.

At one depot site a I tried to persuade a QA chief to allow this maintenance testing... and he pushed-back hard, saying hell-no... until a jet had a major CB panel fire during a return delivery flight... then he "warmed-up" to the idea of simple CB cycling.

Remarkable how You can "feel" a CB that is "not right". We also had a CB tester on-site so suspected CBs could be stress-checked; which proved to be an eye-opener for 'non-believers' when supposedly "good breakers" failed in weird ways.

BTW... one problem that aggravated electrical trouble-shooting as much as CB aging/deterioration was poor cleanlieness within male/female connectors [both sides] and/or bent/loose/sunken pins... especially in large/complex connectors.

Regards, Wil Taylor

Trust Me! I'm an engineer!

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[3DDave]

I am going though the list of specs, got to MIL-HDBK-522, and found a good tip right off:

NOTE: A bright white light (not red or night vision green) with an incandescent (conventional) bulb has been shown to be the most effective in identifying discrepancies. LED light bulbs are not recommended for inspections.

Definitely true on not using the LEDs. Fluorescent lights also have a notched spectrum that can mask color cues.

Thanks!