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Boeing CB statement contradictiom

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Boeing CB statement contradictiom

Old 13th Sep 2015, 04:46
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Boeing CB statement contradictiom

Right I know I only got a B in English at school but still scratching my head on this one;

In flight, reset of a tripped circuit breaker is not recommended unless directed by a non-normal checklist. However, a tripped circuit breaker may be reset once, after a short cooling period (approximately 2 minutes), if in the judgment of the captain, the situation resulting from the circuit breaker trip has a significant adverse effect on safety

So if its not directed and you have a tripped CB, can you reset it.

And then this one;

Flight crew cycling (pulling and resetting) of a circuit breaker to clear a non-normal condition is not recommended, unless directed by a non-normal checklist.

Related am I right in thinking that the LOT 767 crew would have had an easier day if they had checked their panels?
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Old 13th Sep 2015, 07:35
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There is no contradiction there... If it popped out by itself, you can reset it if the commander deems it necessary for flight safety of if directed by a checklist. Recycling a circuit breaker however to reset a system is not recommended.
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Old 13th Sep 2015, 10:28
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Boeing CB statement contradictiom

You should read up on the report of that incident. That particular CB was not immediately obviously involved with the gear, and was not part of the gear checklist. Ask yourself why the technicians on the ground with all that time and diagrams hadn't figured it out.
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Old 13th Sep 2015, 16:40
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I don't see a contradiction there either, but then English is not my native language.
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Old 13th Sep 2015, 18:04
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I have never quite understood this paranoia with regard to the reset of a cb other than the well understood issue of fuel pumps. Certainly, a check of cb panels is a must when things start to go awry; sadly the days of manufacturers supplying a list of circuit breakers on the flightdeck seems to be a thing of the past. In a pevious life, a flight engineer of my mine opened up a panel and used a small piece of silver cigarette paper to jump between two contacts behind said panel - that might be going a little too far today !
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Old 13th Sep 2015, 18:20
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Grades and CBs?

OK, your "B" in English may have been a gift. Native or not, at least we understand your meaning and faaar better than those who write 'Engrish.' Get over it.
I too often wonder about the overly restrictive rules about circuit breakers. There is a huge difference between pulling and then pushing one on your own, as opposed to simply resetting one that has popped on its own. Short of a most critical system, if the books says two minutes for cooling, I'd give it five, kill the on/off of the device where possible and reset Only One Time. (If it burps again or when the device is powered up again, you've got a problem and must fly or divert without that device or system.
References to LOT must refer to their gear-up landing a couple of years ago. Given the length of that flight, I've always been surprised that the pilots, thier own Mx and even Boeing's engineers apparently never tried or suggested a breaker scan or a reset of a specific breaker. As I recall, the bird belly landed and with a critical, gear-related breaker in the OPEN position. I think I also recall that the Mx folks never found any fault other than the popped breaker. Why - I guess we will never know. That said, leaving it open for most of the flight and then resetting the breaker while doing the landing configuration would have posed little or no risk. It is just one of those things that this little brain will never understand. I was not there and there could have been other considerations that did not make it into the final report. There are but a dozen or so folks who do know - and they are not talking.
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Old 13th Sep 2015, 20:26
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B757/767/737: On various occasions a reset CB after a system failure avoided a diversion or AOG. It takes a modicum of common sense & knowledge to know when to give it a try and when not to. Much of manufacturers' speak is legal speak, not technical. If you are in the poo and need to extract yourself then certain sensible resources are necessary. Pulling/Resetting a CB on a failed minor system might be one such occasion. Either that or ignore MEL and pretend failure happened when in flight. The books will try to have you all which way. Black & white it ain't.
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Old 13th Sep 2015, 22:17
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.. keeping in mind, of course, that the label on the CB may not indicate ALL the services which take power from that circuit ie you don't necessarily KNOW what may have a problem ... you just might give yourself an unwanted surprise by playing with the panel.

It gets worse as the electrical/electronic complexity of the aircraft increases ...

Perhaps best to follow the published operational guidance as a general rule ?
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Old 14th Sep 2015, 00:03
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And what do you do when your B787 does not have CB's?

JT does make a very good point though with the increased systems complexity a "simple CB" reset/pull may leave you in a world of hurt that you could not imagine.

One the engineers showed me was the simple park brake, the number of systems that that simple lever affected was astonishing.
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Old 14th Sep 2015, 03:49
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Classic Boeing thinking

Captain's Discretion:

Early final approach, windy and limited tarmac at destination, loss of HYD, ALTN TE FLAPS motor trips. Do you reset?

FWD center tank pump trips. Plenty of kerosene, near end of segment. Do you reset?

APU Fire Bell goes off. APU GCU CB trips. Do you reset?

My decisions would be: Yes, No, and No.
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Old 14th Sep 2015, 03:51
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And what do you do when your B787 does not have CB's?
Send the FO rearward with a schematic and the manufacturer-provided set of wire cutters?
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Old 14th Sep 2015, 04:38
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The B787 does have CBs. They're just not the physical kind. They are accessed on a DU.
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Old 14th Sep 2015, 04:47
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The E170/190 has remote CBs (as well as normal ones) also.
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Old 14th Sep 2015, 05:28
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To those considering resetting CBs against manufacturer's procedures, read this from john_tullamarine's post;

.. keeping in mind, of course, that the label on the CB may not indicate ALL the services which take power from that circuit ie you don't necessarily KNOW what may have a problem ... you just might give yourself an unwanted surprise by playing with the panel.
....and then read it again. And again.

CP
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Old 14th Sep 2015, 05:40
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To those considering resetting CBs against manufacturer's procedures...........
That's just the thing Cap, Boeing leaves room for the commander's discretion for those items not appearing in the NNC as it relates to the continued safe operation of the aircraft. What does that mean? They don't really say. It's one of those things that are decided case by case.

Of course this in no way negates our good Mr. Tullamarine's excellent post.
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Old 14th Sep 2015, 08:57
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The B787 does have CBs. They're just not the physical kind. They are accessed on a DU.
Apart from the normal (thermal) CBs in the aft electronics bay.
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Old 14th Sep 2015, 12:12
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Just to make sure what we're tiling about: there's resetting a popped CB and pulling & resetting CB in the hope of recovering a malfunctioning system. In the former case, if there us enough left to get you home with no action then why risk anything; so leave the CB popped.
In single FMC a/c I've recovered a crashed FMC by pulling/resetting a CB. Indeed, on B757 TR we were taught to do so. B737 I've recovered a dead VHF radio box by pull/reset & a VOR nav box & TCAS FAIL. In all cases I was confident that no other major systems were involved, but the VHF & Nav box being u/s was an AOG(MEL) at next landing.
Regarding connected systems: I heard a story (decides ago) B767. Capt could not engage A/T on takeoff. No problem, it often came in after airborne. 'Cept this time it didn't. He tried a CB pull/reset. However, the EEC's detected this de-powering of A/T as a double engine failure and out dropped the RAT. Captain elected to dump fuel and return. As a result the crew was out of hours and SBY had to be called out etc. etc etc. Once we progressed beyond simple B732 the sparks & electrons of these new fangled beasts move along routes and in and out of circuits we have no idea about.
Another on a B757 was someone trying to recover an IDG he could not get online after engine start. Applying some old B707/727 logic he tried resetting the GCB & bus-tie breaker. Except this action blew up the bus. Ouch.
BEWARE. or bring back those old warriors of yore called FE's. On that subject, I wonder why the pilots' unions and engineering dept of airlines did not insist on having voice communications back to base tech dept once FE's disembarked. Pilots have little tech knowledge, but out on an ETOPS route a cosy chat with a home engineer might solve mean a problem. It did for me when out over mid-Atlantic and the company had SAT phones. B767 mid-90's. Very useful and saved a massive amount in avoiding a diversion & AOG.
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Old 14th Sep 2015, 12:52
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Early final approach, windy and limited tarmac at destination, loss of HYD, ALTN TE FLAPS motor trips. Do you reset?

My advice (as an Engineer with thirty+ years experience) if you're on approach FORGET the damn c/b and fly the damn plane. It takes ages to run down all the permutations of a single circuit breaker popping and the possible affects on seemingly unrelated systems- more time than most pilots have on approach.
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Old 14th Sep 2015, 13:48
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"Early" was the operative word Aveng, that is prior to any stabilised approach SOP. I do get your meaning.

The example was illustrative, but taken to the full stop of your suggestion, go around, land safely with some boards out below.

Last edited by vapilot2004; 14th Sep 2015 at 14:11.
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Old 14th Sep 2015, 15:35
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High power electric motor trips the CB. That is not good. You take a high risk resetting it. Remember the DC-9 and rear toilet motor CB incident that resulted in an onboard fire. The LDR for TE flaps UP is not so great an increase on a dry/good runway. If you are at minimum fuel you still have an ALTN. It would be a bad hair day if that too was as limiting a runway as destination. Electric motors tripping CB could mean mechanical malfunction creating heat, short circuit creating sparks, stuck flaps leading to handling problems, etc. etc. Park it somewhere non-limiting and have a coffee.
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