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Old 24th May 2011, 14:34   #1 (permalink)
 
Join Date: May 2005
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Question Resetting circuit breakers -E170/E190

Hello:

Page I-2 of the E170/E190 QRH states: "Circuit breakers must not be reset."

Now to me there is only one way to read this statement however I have observed the following 2 practices on the line:

1-some consider a reset to take place only when the C/B is pushed back IN after it popped OUT. Accordingly they tell me that pulling a C/B which was not popped and pushing it back IN is not a reset, which makes it an acceptable practice.

2-some consider the above statement to only apply to the thermal C/Bs on each side of the pilots and have no problem with resetting electronic C/Bs through the MCDU.

I believe there might a case for 2 (although I am not sure of the legality of that practice) but I am pretty sure 1 is wrong: any thoughts?

Thank you
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Old 24th May 2011, 21:34   #2 (permalink)
 
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It really says that, in case of smoke or annunciated or non annunciated situation/EICAS message, the checklist asummes that, (among a lot of thing) , you didn't reset any CB.. in other words...... if you have a situation/EICAS message to solve.... you don't touch any CB, just go through the QRH first...
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Old 24th May 2011, 23:42   #3 (permalink)
 
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No specific help on the Embraer series aircraft...

Generally CB reset prohibition is for one of two reasons: Fire prevention, as in the case of fuel pumps, or unpredictable (or predictable but undesired) system reaction/interaction.
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Old 25th May 2011, 09:28   #4 (permalink)
 
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Generally, Maintenance guys call it RESETTING that the C/B is pushed back in after it is tripped due to overcurrent, and also it CYCLING that the C/B is pulled out and then pushed back when any system inoperative needs to be made operative again.

Usually, resetting C/B in flight is prohibited because it can cause much more critical problems than any system inoperative, especially such as fire(fuel boost pump)

please refer to below: it is a B737-800's QRH

In flight, reset of a trippe 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(app' 2 minutes), if in the judgment of the captain, the situation resulting from the C/B trip has a significant adverse effect on safety. On the ground , flight crew reset of a tripped C/B should only be done after maintenance has deternined that it is safe to reset the C/B. 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.
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Old 25th May 2011, 10:30   #5 (permalink)
 
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There is a difference.

As posted, resetting a CB that has tripped in flight is a big no no. They are there to protect circuits from over-current and prevent potential fires etc and as stated require maintenance to find the reason for the trip prior to resetting. They normally trip because they are doing their job!

Cycling CB's on the ground are done to force a particular system to re-boot due to a POST (Power Up Self Test) induced fault. It's a completely different scenario to trips. POST and power transfer induced faults are common in the highly computerised modern aircraft. CB resets are a standard procedure for maintenance. Airbus endorse it often in the Troubleshooting Manual Preamble & Procedures.

Since Embraer's are b@stardised Airbuses with stolen Boeing technology I wouldn't have any issue doing the same!! The other option is ALT CTRL DEL
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Old 25th May 2011, 15:15   #6 (permalink)
 
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Hi,

thank you for the feedback!

I guess I was not clear in my first post: my query is whether it is OK to pull a CB OUT then push it back IN? In other words, the breaker did not pop but I wish to reset the system?

Also, the Embraer in addition to the usual physical CBs also has "electronic" CBs which can be accessed from the MCDU: is it ok to reset them as described above?

Thank you all for your help!
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Old 26th May 2011, 03:47   #7 (permalink)
 
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Quote:
Generally, Maintenance guys call it RESETTING that the C/B is pushed back in after it is tripped due to overcurrent, and also it CYCLING that the C/B is pulled out and then pushed back when any system inoperative needs to be made operative again.
You brought up a good point.

The term "resetting" has been use for both situations. Bottom line is if a C/B pops it is an indication of a problem or potential problem that unless creates a dire safety problem should not be "reset" during flight. FLT800 drove a hightened threat to fuel system c/b's. Your company should better define this.

If you wish to revive a system that has failed (probably best under the guidance of Maintenance CTRL) or a process of your flight manual is normal and common. Pushing in a popped breaker is a dangerous action in flight.
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Old 26th May 2011, 03:52   #8 (permalink)
 
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Quote:
Also, the Embraer in addition to the usual physical CBs also has "electronic" CBs which can be accessed from the MCDU: is it ok to reset them as described above?
Douglass was the first to use RCCB's, same thing just a low voltage control circuit for a breaker in the DC-10 reset the high voltage breaker as opposed to a low voltage signal from an MCDU.
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Old 26th May 2011, 07:51   #9 (permalink)
JAR
 
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From our Company Emb 195 OPs Manual:

Circuit Breakers
If, during flight operations, a system failure is accompanied by a circuit breaker
tripping, one attempt may be made to reset the circuit breaker if:
A reset is specified in the relevant emergency or abnormal procedure.
OR
The system is essential to continued safe flight.
In all other circumstances, circuit breakers must not be reset.
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Old 26th May 2011, 16:13   #10 (permalink)
 
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Generally Embraer is quite clear about CBs:
In flight, a reset is a no no. On the ground, one attempt may be made to reset a popped CB.

You would get the best answer to your question from your Embraer representative. Each company operating Embraer is assigned somebody from Embraer for exactly this kind of question.

If you find out, let us know!
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Old 26th May 2011, 17:07   #11 (permalink)
 
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Take a look at your AOM Vol 1 chapter 4 Intro.

Quote:
- Circuit Breakers must not be reset.
NOTE: Circuit Breakers reset may be preformed when following the limitations and procedures specified in the GROUND RESETS
If you're not sure where that is turn to the back of Vol 1!

There you will find the following quote:
Quote:
LIMITATIONS:
- This chapter shall be used under the following conditions:
- Airplane on the ground with parking brake set;
- Each procedure may be excecuted only once.
and
Quote:
NOTE: This chapter should be used for reference only. Special approval from the regulatory authorities must be granted to use the information herein.
No charge
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Old 26th May 2011, 17:49   #12 (permalink)
 
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Hi!

Thanks for all the replies. I am aware of the ground resets but again my question is:

is it ok to reset (i.e. pull then push back) a CB which did NOT pop?

For example, you get "TCAS FAIL" during taxi: is it acceptable to reset the electronic CB (which shows IN) via the MCDU?

I know this works most of the time, I just don't know if it is acceptable/legal.

Thanks.
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Old 26th May 2011, 19:46   #13 (permalink)
 
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Ask Embraer!
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Old 26th May 2011, 21:23   #14 (permalink)
 
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Agree that for the official answer you need to ask Embraer (and possibly your own NAA, since they may have an opinion too)

In the context of that latter point, Transport Canada have a fairly firmly held opinion that Circuit Breakers are not switches, are not designed to be used as switches, and therefore should not be used as switches. Routinely using a CB as a switch may well result in usage (and wear, for example) of the CB to the point where it is no longer as reliable in performing the essential function for which it was installed on the a/c.

You may be able to argue that point with an electronic CB, but for actual physical units, TCCA have even been resistant to the use of CB pulls or resets to mitigate failure cases (pending a 'proper' fix) since it goes against their CB philosophy.

Obviously, your NAA may have a different take on the matter.
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Old 27th May 2011, 04:05   #15 (permalink)
 
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Quote:
For example, you get "TCAS FAIL" during taxi: is it acceptable to reset the electronic CB (which shows IN) via the MCDU?
During taxi, I would, even in flight, a TCAS FAIL is not a catastrophic situation. But first I would try try to reset the equip. or switch to the other.

There are situation that are common sense... like TCAS FAIL.. or RALT FAIL..
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Old 27th May 2011, 04:09   #16 (permalink)
 
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Usually in older planes, just one reset is allowed after waiting for a cool period (thermal CB)

Electronic CB are different ( I don't know much about them) but I guess they are like virtual swithes. But always just one time, no more
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Old 27th May 2011, 07:16   #17 (permalink)
 
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Thank you all for your kind assistance!
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Old 27th May 2011, 07:28   #18 (permalink)
 
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Reminds me of the first time I flew a Bristol Freighter after having discovered how to get to its flight deck/cockpit.

Notes said turn on the fuel booster pumps. Spent 10 minutes looking for the switches which didn't exist. Found the pump CB's and hey presto - they were used as the switches. Didn't care for that.
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Old 27th May 2011, 14:52   #19 (permalink)
 
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The documentation is quite explicit. The answer is quoted several times in this thread.

Quite simply NO!

CB should only be tripped or reset or cycled(Embraer do not use this term) as directed by the published procedure in compliance with the certified limitations of the aircraft and your local approvals which will never be less limiting.
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Old 27th May 2011, 16:11   #20 (permalink)
 
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Some general advice

To start off; I know nothing about this specific model.

1. Follow the checklist.
2. If the flight crew deems resetting or cycling a breaker necessary for safety reasons, keep the following in mind:

Resetting a tripped breaker (closing a breaker into an existing fault) has the potential to damage the breaker itself. Now you have two problems: The original fault and a failed (perhaps welded contact) breaker.

Cycling a breaker for a non-responsive system can result in that system 'latching up' in some undesired state. Some systems have alternate sources to which they will transfer and perhaps remain. Others have sufficient stored energy (usually incorporated to allow microprocessors to ride through power glitches) that a quick c/b cycle may not result in a system reboot. For example, remote sensors may go down while the processor continues to monitor them, resulting in the processor storing their status as failed.
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