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Fire Extinguishers in Aircraft Engines

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Fire Extinguishers in Aircraft Engines

Old 5th Aug 2009, 03:02
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Fire Extinguishers in Aircraft Engines

I have been told previously that the fire extinguishers on the end of the Fire Handle / button / lever were 'engine wreckers' - if you fired the extinguisher into the engine, the engine would suffer damage from the extinguishant that would render it good for nothing but scrap.

You might argue that you would only fire an extinguisher into an engine that was burning so who cares whether it ended up as scrap.

But what if you were receiving ambiguous indications and that 'you thought' the engine MIGHT be burning ?
If you fire the extinguisher into the engine 'just in case' and the engine was in fact NOT on fire, have you damaged the engine beyond repair ?

Thanks in advance for your replies.

Cheers,
Wings
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Old 5th Aug 2009, 09:18
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if you fired the extinguisher into the engine, the engine would suffer damage from the extinguishant that would render it good for nothing but scrap.
I think you have a misunderstanding here. The extinguishant (on every type I have been familar with) is not discharged into the engine, but into the nacelle or engine bay, outside the engine casing. There is constant fire inside a turbine engine - the absence of it is called a flameout. If there is fire in the engine bay or nacelle, you have a major problem, and that is where the extinguishing agent will go.

Does it wreck the engine? Not as much as a continuing fire would.
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Old 5th Aug 2009, 09:58
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If the aircraft Halon system has been operated whilst the engine is above max continuous,then the engine case is inspected/washed with water,other than that (always assuming it was a spurious warning) no action required.

If a ground fire occurred & extinguishant has entered the core it could vary from a wash/inspection to engine removal for a shop visit;Although this would all be dependant upon the type of extinguishant employed.
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Old 5th Aug 2009, 11:03
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Agreed. Extinguishant is discharged into the cowling around the engine. A quick wash and wipe and new bottle and away you go! It might help also to repair the original problem.
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Old 5th Aug 2009, 11:52
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I think that the confusion here lays with the use of External Chemicals. This topic normally comes up when talking about "Tail-pipe" fires,

Because the external chemicals are highly corrosive their use is not recommended WHEN POSSIBLE. Example: Engine Fire during start / shut down... "...Use bleed air / ground starter air to extinguish..." The remaining issue, is determining if it is a tailpipe fire, or a fire that can be combated with the on board equipment (within nacelle/cowlings, etc)

In-flight engine nacelle fires present different issues. Recently two 767 pilots operating for a Japanese based carrier blew both bottles when they experienced an engine fire during take-off. Both of them were presented with awards from their company for "Wrecking" that engine.

Which brings us to "Wrecking". I'm not sure I agree with this. Many years ago (about 16) a colleague operated an aircraft which was subsequently found to have had one of it's extinguishers discharged. The aircraft (Shorts Sky van) was operated like this for some time before the discarged bottle was was discovered (apparently an intentional coverup) I don't recall that the engine was damaged to any extent. Maybe one of the Engineers in this forum can speak more intelligently on this item.


Enter the issue of "Ambiguous Indications". The outcome of this scenario will be subject to the experience of the crew and other factors. An experienced group of folks may (or may not) see other factors (Bleed Air Leak, etc) and realize that a few seconds of thought before pushing that button or pulling that handle may yield a different end result. Additionally, an understanding of the type of fire detection system installed on the aircraft may prove beneficial.

Examples:

Photocell type detector which detects light - A slight change of heading or bank angle, and the fire disappears. Engine Fire? Without any other indication, I'd say ...probably not.


Heat Detector type - Pull thrust toward idle and fire warning quickly goes out. Move it forward again, slowly, and at some point the fire warning returns. Probably a bleed air issue, but again, will need to quickly review other indications.

There are several other examples which come to mind, and each would be handled according to their individual experience levels and circumstances.

That said, when it comes to safety, and more appropriately when it comes to an event that has compromised safety, the cost incurred with any successful solution (Extinguishing the fire) is irrelevant.

The bottom line; take a short moment to consider all the indications before deciding on the course of action, then do what's necessary to ensure a safe outcome.

On a similar, but separate subject. The chemical may (or may not) be corrosive, but they are definitely environmentally unfriendly. A few years ago some studies were conducted which looked at alternative types of extinguishing agents.

That study can be read here.

http://www.fire.tc.faa.gov/pdf/engine.pdf
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Old 23rd Aug 2009, 10:31
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Extinguishing agent is ported to the Exterior of the engine,below the Cowls.
regds
MEL.
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Old 23rd Aug 2009, 15:25
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Depends on the extinguishing media.

Halon is a low-specific-heat gas that does not result in shock cooling of the hot engine cases, and is thus fairly benign to an engine's integrity.

Other gases - perhaps more environmentally friendly - have higher specific heat values, and the shock cooling they cause is not good to compressor/turbine cases, which after all are highly loaded pressure vessels.

So the choice of extinguishant is a tug-of-war between the engineering camp and the greenies.
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Old 25th Aug 2009, 10:17
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Fire Extinguishers in Aircraft

Wings, fire extinguisher systems fitted to aircraft are there to help save lives and airframes, not for any other reason. The last thing a pilot confronted with an engine fire would be considering would be the effect on the engine of using the fire extinguisher. As others have said, the extinguisher agent does not get injected into the engine, but into the engine nacelle. Additionally, when the Fire Handle or Fire Switch is activated, as well as arming the extinguisher system, all flammable liquids to the engine are shut off as is bleed air if applicable. As I said, the sole purpose of the fire extinguishing system is to extinguish any fire which occurs within the nacelle.
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Old 25th Aug 2009, 13:31
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Ummm let's see... fire on the jet? I think you got a lot more to worry about than saving the company money on a new engine. Besides... that's why god invented insurance, and warranties
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