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A320 Engine Fire System Question

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A320 Engine Fire System Question

Old 5th Aug 2009, 12:43
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A320 Engine Fire System Question

Hi

Can anyone shed any light on how Squib A and Squib B are controlled? When you press the BTL 1 button in the flight deck - does the system use squib A, squib B or both to discharge bottle 1? Can the flight deck influence which squib is used?

Basically, I am in the dark as to how the squibs fit into the engire fire protection system. Reference is made to squib A and squib B. Is there a squib A and B for bottle 1 AND a separate squib A and B for bottle 2?

Classic case of a picture speaking a 1000 words. I do not have access to any engineering diagrams which show the relationship of SQUIB A and SQUIB B to fire bottle 1 and fire bottle 2?

Thanks for any thougts.

Peter
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Old 5th Aug 2009, 13:44
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Try this

SmartCockpit - Airline training guides, Aviation, Operations, Safety
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Old 5th Aug 2009, 14:30
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Hi Happybiker

These are the manuals that I have been reading.

Unfortunately, they do not answer my query.

Any other suggestions anyone?

Thanks

Peter

Last edited by Butter side-up; 5th Aug 2009 at 14:31. Reason: Typ
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Old 5th Aug 2009, 15:20
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Peter , there are 2 bottles for each engine (located in the pylons fwd and aft of the round access panels you can see).
Each bottle has one squib.
Press the left switch (AGENT 1) and Bottle 1's squib fires.
Press the right switch (AGENT 2) and Bottle 2's squib fires.

Both bottles share a common discharge pipe.

Same system for the CFM or IAE engine.
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Old 5th Aug 2009, 16:53
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Devil

Fargoo

Thanks for the reply.

I thought that the system set up was as you described - until I read the following in the Electrical Supply section of the Fire Protection chapter in the systems manual that we have:

BTL 1 SQUIB A - HOT 1
BTL 1 SQUIB B - HOT 2
BTL 2 SQUIB A - DC 2
BTL 2 SQUIB B - DC 2

Here it talks about BTL 1 having squib A and squib B - and similarly for bottle 2.

This is why I am confused - does each fire bottle have two squibs (if so, why need two)?

Or does each engine have two squibs - EACH of which could discharge bottle 1 or bottle 2 for that engine? If so, is the above saying that the firing mechanism for the squib to fire into bottle 1 is suppplied of separate HOT buses, whereas the firing mechanism for the squib to fire into bottle 2 is supplied by the DC bus? Which squib is used when you fire the Agent 1 switch in the flight deck into a particular engine - squib A or squib B? Does it depend on whether Agent 2 has been fired (out of sequence) into that engine? Is squib A always the first to be fired? So many questions!!!

It seems amazing that there is not an Airbus diagram to illustrate this!

Any thoughts?

Thanks for taking an interest. Life goes on - but I would like to get to the bottom of this in time.

Peter
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Old 5th Aug 2009, 18:48
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More confusion

Each squib has two filaments, for bottle one on each engine there are two independant 28v circuit breakers supplying from the hot battery bus.

For bottle two on each engine there are two independant 28v circuit breakers supplying from the 28v DC BUS 2.

To summarise, each engine has 2 bottles. Each bottle has one squib. Internally each squib has two filaments in case of failure of a filament. Bottle one both filaments supplied from Hot Bat Bus. Bottle two both filaments supplied from DC Bus 2.

Hope this makes things clearer
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Old 5th Aug 2009, 19:02
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On top of that, firing order.

Simple.

If you press the Agent 1 button then Bottle 1's squib will fire.

If you press the Agent 2 button then Bottle 2's squib will fire.

There is no link to stop you firing No 2 first but SOP is to fire No 1 Agent then wait 30 secs and if you still have the fire warning fire No 2 Agent.

Hope this helps
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Old 5th Aug 2009, 19:25
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Fargoo

That certainly does help - and makes sense.

To test my understanding....

Would you agree that the reference to BTL1 SQUIB A and BTL1 SQUIB B in 1.26.60 could more illustratively clearly have been written as:

BTL 1 SQUIB - Filament A and
BTL 1 SQUIB - Filament B?

Do you have any diagrams showing ONE squib per bottle - and two filaments in that one squib?

Thanks

Peter
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Old 5th Aug 2009, 20:10
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I do agree it's badly worded. The C/B's are labelled BTL1 SQUIB A etc too which adds to the confusion!

This diagram should help



It illustrates No 2 Engine bottle 1 being fired. Bottle 1's squib is being supplied with two 28v dc supplies from the hot bat bus through the fire handle switches and finally passing through the depressed AGENT 1 pushbutton switch.

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Old 5th Aug 2009, 21:04
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Fargoo

Thanks for that.

Doubtless I can get less out of that diagram than you - but it does confirm you earlier explanation.

All the best

Peter
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Old 5th Aug 2009, 21:39
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No problem, here's an image that shows the engine bottle with just one squib also.

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Old 7th Feb 2023, 16:49
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Hello
I know it's very old post, but it seems to very interesting discussion. I have a question related to this. In the MEL for Fire protection (chap26), for Engine 1 loop A and engine 2 loop B, it mentions no ETOPS beyond 120min. Is that because those loops are the masters of each engine respectively ? I thought all loops are identical.
Quite confused by this. Thanks for any explanation.
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Old 10th Feb 2023, 11:57
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Squibs (or initiators) are electrical ignition devices that are used to activate various fire protection systems, including aircraft fire suppression systems. A squib typically consists of a small explosive charge that is detonated by an electrical current, which in turn ignites a pyrotechnic charge or opens a valve to discharge the fire suppressant.

In an aircraft fire suppression system, there may be two or more squibs per fire bottle, with each squib serving as a backup in case the other fails. These squibs are typically labeled as "Squib A" and "Squib B." The flight deck usually has a control panel that allows the crew to activate the fire suppression system, which then triggers one or both of the squibs.

The exact method of control depends on the specific design of the fire suppression system, but in general, the flight deck can choose which squib to use or use both squibs simultaneously. The choice of which squib to use may be based on factors such as the severity of the fire or the amount of suppressant remaining in the bottle.

In summary, there may be separate squibs A and B for each fire bottle, and the flight deck can usually select which squib(s) to use in an emergency. However, the exact configuration and control of the squibs will depend on the specific design of the aircraft's fire suppression system.
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