Can smoke detectors really detect methane?
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Can smoke detectors really detect methane?
If so, what else? From Aviation Herald;
"A Singapore Airlines Boeing 747-400 freighter, registration 9V-SFI performing flight SQ-7108 from Adelaide,SA (Australia) to Kuala Lumpur (Malaysia) with 4 crew and a cargo of 2,186 sheep, was enroute at FL320 about 400nm south of Denpasar (Indonesia) when the crew received a smoke indication in a cargo bay, descended the aircraft to FL250 and diverted to Bali Denpasar for a safe landing about 45 minutes later. Emergency services did not find any trace of fire, heat or smoke.
The smoke indication was identified to be the result of exhaust gasses and manure produced by the sheep.
The aircraft was able to depart again after about 2.5 hours on the ground in Denpasar and reached Kuala Lumpur about 2.5 hours later."
Incident: Singapore B744 near Denpasar on Oct 26th 2015, sheepish smoke indication
"A Singapore Airlines Boeing 747-400 freighter, registration 9V-SFI performing flight SQ-7108 from Adelaide,SA (Australia) to Kuala Lumpur (Malaysia) with 4 crew and a cargo of 2,186 sheep, was enroute at FL320 about 400nm south of Denpasar (Indonesia) when the crew received a smoke indication in a cargo bay, descended the aircraft to FL250 and diverted to Bali Denpasar for a safe landing about 45 minutes later. Emergency services did not find any trace of fire, heat or smoke.
The smoke indication was identified to be the result of exhaust gasses and manure produced by the sheep.
The aircraft was able to depart again after about 2.5 hours on the ground in Denpasar and reached Kuala Lumpur about 2.5 hours later."
Incident: Singapore B744 near Denpasar on Oct 26th 2015, sheepish smoke indication
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Extremely unlikely and a candidate for Snopes.
The methane molecules are too small to be "seen" by the detectors. A less gullible explanation would revolve around dust or fleas.
The methane molecules are too small to be "seen" by the detectors. A less gullible explanation would revolve around dust or fleas.
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Are ionisation type detectors still used on aircraft? The standard cargo smoke detector just uses a beam of light and a light sensor (photo cell). An air sample is sucked through the detector and smoke increases the amount of light reaching the sensor.
It's not unknown that excess moisture in the air (due to various factors, including animal waste products) causes condensation on light emittors/sensors and causes the cargo fire test to fail. However, for a smoke alarm, two sensors need to be affected.
It's not unknown that excess moisture in the air (due to various factors, including animal waste products) causes condensation on light emittors/sensors and causes the cargo fire test to fail. However, for a smoke alarm, two sensors need to be affected.
From past experience it would seem the cause is a build up in humidity. Recall an aircraft having to turn back with a similar problem in Australia.
http://www.skybrary.aero/bookshelf/books/2086.pdf
http://www.skybrary.aero/bookshelf/books/2086.pdf
Are ionisation type detectors still used on aircraft?
Boeing uses both technologies in some aircraft. However it appears from the info on Boeing's website that the 747-400F uses photoelectric sensors exclusively.
The wave of the future as far as optimal smoke detector performance is concerned appears to be with integrated multi-sensor detection systems utilizing 2, 3 or more detection technologies.
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Ionization type detectors are flying all over the world on a variety of different aircraft types right now!