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rsrandazzo

engine flame out

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Ben-A "Flame Out" is when the engine stops running for unknown reasons. ie: "The flame insdie the engine goes out." Could be caused by a wide range of mechanical problems.An "Engine Fire" may or may not mean that you have a fire in the engine nacelle. There is no such thing as a fire detector, per se- so what you have are some temperature sensing loops that provide monitoring of the temperature inside the nacelle areas, but outside the actual engine core itself.If the temperature in the nacelle area rises above a particular temperature limit, OR if the sensing loops lose conductivity for unknown reasons, you will get a fire warning for that engine. I believe the temperature limitation in this case is 325C (might be 425, I'm a bit fuzzy on it right now.)So- to recap:Flameout: The flame that should be on the inside of the engine goes out.Engine Fire: You might have flame in places around the engine that you shouldn't. Hope that helps. ;-)


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Guest D17S

Don't know if you're interested in this level of detail, but there are a couple of types of fire loops these days. I think the one Robert was describing is the one that is built, well, kinda like a coax cable. There's an inner conductor, an insulator around this inner conductor and an outer conductor around that. The insulator between the inner conductor and the outer conductor is heat sensitive. At X degrees, this insulator starts to loose it's ability to insulate. As this insulator starts to loose it's insulating capability, electricity (current / amperage) actually begins to flow between the two conductors. There's a current monitor that constantly watches this. Like any good chaperone, it wants to see no contact between these conductors . . . and just like in real life, one conductor is fully charged and ready to go and the other, prudently well grounded. Ideally, the current monitor chaperone wants to see no electricity flowing between these two. But as soon as it sees just too much current flowing between the two conductors, it hits the fire bell. Fire warning. (Dang. Busted again!) Newer types use gas filled tubes with pressure sensors at the ends (see it coming?) As the gas heats up, it expands and pressurizes the tube. As things heat up, the pressure senders will sense this increase in pressure and finally ring the bell too. (Another "learning tool" analogy for this one? . . . Anyone? Robert's giving a prize.)

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Hi,1) as long as the temperture rises to a certain level in the nacelle, no matter there is fire or not, the fire warning will horn? 2)And even though the fire extinguish itself rather than by the crew's action, the fire horn will still be actived?3) if the fire horn goes on, it may be caused by engine fire, flame out, or loop failure, is it correct?4)when engine horn goes on, the pilots need to address it immediately, is it correct? Or there is time tolerance for it. that's mean when we have engine failure after V1, should I rotate and stablize the aircraft (ie gear up, climb out at V2) first before addressing the fire issue. Sorry for asking so many question, but I want to know something in detail. thanksben

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Thanks you very much...learning doesn't hurt...However, I think 744 and A340 are using wire, is it correct? and how about the 777 GE90 engine, is it using the gas one??thanks againben

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Guest D17S

You got it. The fire sensing / detection system has nothing whatever to do with flames or actual fires . . . other than flames and fires tend to throw off just a bit of heat! All the detection system can tell about is heat. We get fire warnings for just bleed air leaks from nacelle pneumatic ducting from time to time. So if the fire went out all by itself, the system wouldn

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Fire detection systems are a lot smarter than they used to be. 744 fire detectors know the difference between a fire and a fault by the way the loop electrical resistance changes.The fire detection loops are in pairs (both loops need to detect a fire before a fire warning is sounded). Dual loop faults are dual faults, and do not generate fire warnings. If one of the loops fails, then the detection system reconfigures to sound a fire alarm if the remaining, operational loop senses a fire.The RB211 has an additional overheat (and test) system, called the turbine overheat system. A second test button can be found on the overhead panel. It's not modelled in the sim, but it basically monitors the turbine case cooling system.Cheers.Q>

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"1) as long as the temperture rises to a certain level in the nacelle, no matter there is fire or not, the fire warning will horn?"I'm not sure how you'd generate so much heat without fire. There are detection loops around the bleed air components on a CF6 engine, but these generate OVERHEAT Cautions rather than fire warnings. I'm not sure if this is what Sam is referring to or not. "2)And even though the fire extinguish itself rather than by the crew's action, the fire horn will still be actived?"The fire detection system and the fire extinguishing system are independent, so the horn and visual warnings will remain whilst the fire is active... and should go away when the fire no longer exists. The crew, of course, can manually cancel the noise at any time.3) if the fire horn goes on, it may be caused by engine fire, flame out, or loop failure, is it correct?NO fire warning will result from a loop failure on the 744. Fires generate an increase in resistance and capacitance in the loops over a certain timescale. With this data, the detector system is capable of distinguishing between faults and fires."4)when engine horn goes on, the pilots need to address it immediately, is it correct? Or there is time tolerance for it. that's mean when we have engine failure after V1, should I rotate and stablize the aircraft (ie gear up, climb out at V2) first before addressing the fire issue."The engine fire warnings are inhibited during critical stages of flight. You will not know if there is a fire between V1 and 400' Radi Altitude. If V1 is unknown to the aircraft, the inhibit starts at a certain angle during rotation. If the aircraft fails to reach 400', the warnings will appear after a certain time delay.Hope this helps.Cheers.Q>

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"Fires -do not- generate increases in resistance."Correct... a simple slip of the tongue on my part... trying to consolidate notes from a variety of sources."Faults generate increases in resistance."Depends on the fault. My training notes on Graviner fire detection systems say that a "normal fault" is a short to ground."Nothing in a fire loop creates any kind of capacitive property."Also depends on the system. This is why detector cards have to match the type of loops fitted to an engine.Quote from some 744 training notes on the Graviner System:"The system monitors resistance for fault detection and capacitance for fire detection"Let the games begin...Cheers.Q>

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Guest D17S

Short to ground of what? There are probably thousands bits and pieces to this system. (It's true

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"I agree completely that an excessively low resistance to ground (of this mystery component) should latch a fault. But I would be concerned if this was the only way this system could detect a fault."It's not the only way....On the Graviner system:Short circuit: One that will register a fault without testingOpen circuit: One that will show when a (cockpit) test is performed"So the question becomes "What is this mystery component that shorts to ground to produce a fault?" You would have to ask the designer why he/she chose to produce a system which makes you do a test to find a particular type of fault, but shorts could come from any number of components in the Graviner system. The loops not only consist of the harder metal-sheathed sensing elements, but also normal interloop wiring. Actually, the sheathed elements on the Graviner system are not the most rubust of engine components and can be crushed causing a short between inner and outer (the outer is grounded).The Graviner type sensing loop has a single copper wire inside the metal sheath, unlike the Kidde loop which has two conductors inside the sheath (as you described). If Ben is looking for (ultra) specifics, then I apologize.... My intent with most of my messages is to make them as palatable to the general reader as possible.Cheers.Q>

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Guest D17S

Well said. also: "You would have to ask the designer why he/she chose to produce a system which makes you do a test to find a particular type of fault, but shorts could come from any number of components in the Graviner system."Does this mean I can put away my DVOM and my megger and just press a button? Please say it isn't so! I was actually kinda disappointed when they updated the 747-200s with a central digital fuel quantity processor unit (CDFQPU? heck, I don't know). But the point was that the dang thing constantly monitored the HiZ and LoZ circuits (and the implied capacitance). The crazy thing even had a TDR (time domain reflectometer. . like radar for wires) function that could tell you not only what wire was broken, but where it was broken. And here I'd been the sorcerer with my mysterious and magicly test boxes all these years . . . and now all anyone has to do is go push a button. Progress? Gotta say yes. But, hummm. Sadly, it's becoming less and less important to even know how this stuff works . . . it's passing to the next generation. It

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