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-   -   Military policy on cycling CB's (https://www.pprune.org/military-aviation/619121-military-policy-cycling-cbs.html)

Chris Kebab 7th Mar 2019 14:01

I think it's fair to say that going back several years there was a - erm - lets say experience based pragmatic approach to the "management" of CBs by aircrew which did vary aircraft to aircraft. I am not aware it is encouraged any more!

Pontius Navigator 7th Mar 2019 15:20


Originally Posted by Radley (Post 10408290)
OAP, more so these days but back in the day when out in the Atlantic trying to keep hold of a slippery Akula you did what was necessary, safely and with knowledge, to get the job done.🤓

On Ops you do everything possible to get the kit working. Even fuse changes and resetting CB on nuclear weapons control systems was SOP. If necessary you would hold the CB in if it meant it worked. If a fuse blew, try a bigger fuse if the difference was success or mission failure. In modern ops, with so few aircraft and mass delivery of weapons, the whole ethos now is to preserve the aircraft and not press on to the target.

Prosecuting an SSN falls in to the bracket where you need to hang in there.

NutLoose 7th Mar 2019 22:45

The mighty Cessna 152 actually has a self resetting CB in the field circuit, it works on a bimetallic plate and trips and resets itself.

GlobalNav 8th Mar 2019 01:59

Circuit Protection
 
In spite of common practice and years ago even part of design and approved procedures, there is a safety objective behind avoiding excessive cycling of circuit breakers. It weakens them over time and diminishes their protective capabilities. FAA requires switches and controls be used instead of CBs for routine on/off purposes.

BEagle 8th Mar 2019 11:01


Even fuse changes and resetting CB on nuclear weapons control systems was SOP. If necessary you would hold the CB in if it meant it worked. If a fuse blew, try a bigger fuse if the difference was success or mission failure.
So whilst chasing some 'slippery Akula', you would hold in a tripping CB? What utterly crass folly which could have led to a fire, loss of aircraft and crew.....:rolleyes:

weemonkey 8th Mar 2019 11:14


Originally Posted by GlobalNav (Post 10410043)
In spite of common practice and years ago even part of design and approved procedures, there is a safety objective behind avoiding excessive cycling of circuit breakers. It weakens them over time and diminishes their protective capabilities. FAA requires switches and controls be used instead of CBs for routine on/off purposes.

Yes. 40 odd years of tripping white area cb's certainly proved that point.

On ops with a.c. armed, tripping and resetting certain cb's is about the only thing you can do to clear a fault without getting the a.c. downloaded...

NutLoose 8th Mar 2019 12:38


FAA requires switches and controls be used instead of CBs for routine on/off purposes.
Most modern light stuff combines the two as shown in the example below, the toggle switches also incorporate a built in CB as denoted by the value on the end of the toggle and trips the switch into the off position.


https://cimg4.ibsrv.net/gimg/pprune....e535d73ce7.jpg



ivor toolbox 8th Mar 2019 14:28


Originally Posted by Vendee (Post 10408260)
I'm reminded of the A340 ground incident at Toulouse during a high power engine run when the engineer pulled a CB to silence a noisy config warning. Unfortunately, the CB in question (ground proximity sensor) corrected the config error by putting the aircraft in a flight configuration, which meant releasing the parking brake. No chocks were fitted and the aircraft was destroyed.


Think it was not the engineer actually in charge of the run that pulled the cb, but someone else who was in a party of observers from the customer.

And as for holding tripped CB's In, if they keep tripping, well you can if you just want to exercise your fingers, for many years they have had to be trip free ( IE if tripped, and the condition that caused it is still present, will stay tripped internally even if one keeps a pudgy finger on it) in aviation applications.

Ttfn

Ttfn


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