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

punkalouver 6th Mar 2019 03:56

Military policy on cycling CB's
 
Seems to be a bit of a no-no on the civilian side but what about in the military. An F-14 story I read recently was quite interesting. Of course...it is during combat ops.

"Another mission that stood out was one I flew with LT Larry "Lobes" Sidbury. Lobes was our Training Officer, a phenomenal pilot and warfighter, later he became CO of VFA-31. Anyway, on deck we had an error with the AWG-15 Stores Management System, meaning if it couldn't be fixed we couldn't drop bombs. Lobes said we'd launch and try to figure it out airborne. Airborne I ran all the bits, pulled the circuit breakers and yet the error held firm. I asked Lobes if we should notify the ship and let them launch the spare. He said "hell no, keep pulling the breakers, you have two hours to get it working!" The Tomcat had over 100 circuit breakers in the back that the RIO could access and it was common practice to cycle them to get the offending system back on-line. Well I kept cycling the breakers and low and behold after about an hour we were back in business"


Vendee 6th Mar 2019 07:39

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.

Onceapilot 6th Mar 2019 07:49

Punka, Mil aircraft operate within a framework of regulations, orders and SOP, just like Civ aircraft. The implications of cycling CB's are similar and, subject to specific proceedures according to type and operator, as you would expect. :)

OAP

Radley 6th Mar 2019 08:06

CB the pulling of
 
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.🤓

TURIN 6th Mar 2019 09:11


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.

If you mean this one Etih....A340 Toulouse then no. CBs had nothing to do with it.

NutLoose 6th Mar 2019 09:33

Remember the RAF Tristar :)
seized pump and holding in a CB on a run ( BA eng ) resulted in explosion of said pump with a fire to boot and a lot of damage in the wing.


..

BEagle 6th Mar 2019 09:45

During my F-4 course, my nav reset a tripped radar CB about 12 times before letting me know.

I suggested that it might be trying to tell him something and to leave it tripped!

Airbus were rather surprised to learn that resetting tripped CBs was quite routine in the VC10 - whereas in their aircraft it most certainly was not!

Saintsman 6th Mar 2019 11:19

Almost the same as resetting CB's. 'Black' Boxes were routinely re-racked to cure faults.

bvcu 6th Mar 2019 16:54


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.

Not quite correct ! Airbus park brake was not full pressure so on high power run you use one guy on toe brakes to get full pressure. However the ran all 4 engines at high power which no brake system will hold !

ShyTorque 6th Mar 2019 17:09

There is no one answer, military or civilian. The pertinent flight manual for the type is the place to look.....

Lyneham Lad 6th Mar 2019 17:50

Cycling CB's. The aeronautical equivalent to the IT Dept's "do a reboot..."

H Peacock 6th Mar 2019 17:50

There's a huge difference between resetting a non-tripped CB and resetting a tripped CB.

If you know your systems well enough then why not pull the Stores Management computer CB to reset it? It's being used simply as an on off switch. I have done this many times in an attempt to bring a piece of kit on line and often works. That said, you have to know that turning said piece of kit off won't cause further problems.

Resetting a tripped CB can be done with caution, but as for holding in a tripping CB that's asking for trouble.

Onceapilot 6th Mar 2019 17:52


Originally Posted by ShyTorque (Post 10408763)
There is no one answer, military or civilian. The pertinent flight manual for the type is the place to look.....

Yes, I tried to extinguish this dopey thread on my reply @ #3. :rolleyes:


OAP

ORAC 6th Mar 2019 19:38


Dan Winterland 7th Mar 2019 03:20


Airbus were rather surprised to learn that resetting tripped CBs was quite routine in the VC10 - whereas in their aircraft it most certainly was not!
The A330/340 doesn't have CBs accessible in the cockpit - they are all under the floor in the radio electrics bay. There are some reset buttons which look a bit like CBs on the overhead panels, mainly for computers, but CB resets in flight aren't allowed or even possible without going 'downstairs'. If a CB pops, the monitoring system lets you know and you can see which one by looking at the CB systems page on the alerting system.

BEagle 7th Mar 2019 04:27

Hi Dan - I was referring to the A310MRTT. There are some CBs at the Fuel Operator's Station and I was developing abnormal procedures. If a pod failed to respond when the master p/b was pressed, I asked whether the CBs should be checked and if one had tripped, it could be reset.

Much sucking of teeth and "No!" was the answer.

Two's in 7th Mar 2019 12:14


Originally Posted by H Peacock (Post 10408792)
There's a huge difference between resetting a non-tripped CB and resetting a tripped CB.



This!

Resetting a tripped CB is a great way to practice your "Smoke in the cockpit" drills. Using it to cycle a serviceable system is not a terrible idea at a pinch, but ignorance is not bliss when switching power in and out.

TURIN 7th Mar 2019 13:09

The A320 even has an AMM reference for 'computer resets' in ATA chapter 24. Very useful. :O

Surplus 7th Mar 2019 13:23

I guess it depends on the A/C type. Resetting CB's on one A/C was normal (I'm not talking about tripped ones.) Another Air Force and aircraft type it was taboo and they lost a lot of sorties because of it. Who was right?

Timelord 7th Mar 2019 13:34

A USN E2 dropped into Lossie for fuel late one Friday afternoon for fuel en route to the Farnborough air show. Unfortunately the VASS power set seemed not to be compatible with the E2 systems. Every time they tried to start the engines all the power tripped off. With rapidly approaching airfield closures at Lossie and Farnborough the Aircraft Commander and I were trying to get Oceanic to talk to their C130and get it diverted in, , trying to keep the airfield open, talking to Farnborough etc when the VASS sergeant came in and announced all was well, the engines were running and would the AC like to get aboard. Once they were on their way I asked the VASS guy how he had done it, “Easy” he says,” their crew chief in the cockpit, and me in the power compartment holding the CBs in”

I’m not sure that was actually “policy” though!

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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