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Comment by bb101 | Hacker News Reader

I've read a few posts on here about people getting off their A380 flights feeling better sans dry throats, chapped lips, etc. I find that a bit odd, as the A380 still uses bleed air systems, unlike the A350 and 787 which use filtered air. All other factors being equal, there should be no difference between air quality on a 777 and A380. Perhaps I'm missing something?

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All bleed systems are filtered. The comparison you meant to make is between bleed air and air delivered by electric compressors, as on the 787.

The A350 & A380 (and all current Airbus airliners) use bleed air from the engines, just like all other airliners bar the 787.

The reason that people feel better after long flights on more modern aircraft like the A380, A350 and 787 than they do on older aircraft is due to lower cabin altitude and thus higher cabin humidity, which is largely down to the use of more composites in the construction, which can handle the higher humidity without corrosion problems. This better cabin environment is possible with bleed air or with electric compressors.

As an aside, the 787 also offers some protection from "fume events" (leakage of combustion byproducts or oil fumes from the engine into the cabin) since it doesn't use bleed air. However, there's still oil in the electric compressors so there's still some (much diminished) risk of fume events.

The likelihood of an incident like that even with a bleed air system is rather tiny, considering the air comes from the cold bypass section of the engines, and there's a redundancy in that multiple engines are available to provide it. If all your engines are emitting fumes, you have bigger problems than the air quality in the cabin (and you have oxygen masks to deal with it)

It's true that fume events are rare, but they do happen. It seems that leaking seals are one cause. If you search aviation incident databases there seem to be one or two reported fume events somewhere in the world per month on average, which is indeed a tiny incidence compared to the volume of air traffic.

There is actually quite a few fume evenths monthly, and a rather concerning report[1] from one of them.

[1] http://avherald.com/h?article=4b6eb830/0006&opt=7168

Fume events are rare as long as you define them as being above regulated threshold of contaminants in the cabin. This is fine for most people, but others (my partner included) have sensitivities to the contaminants, which trigger neurological symptoms whenever she flies, even in "safe" conditions. These days she wears a mask whenever flying and doesn't get symptoms - except the 787, where it's not necessary.

Before we worked out the issue (the risk of which really should be communicated by airlines) she was sicks for weeks after flying. And although unlikely, she once was caught in a fume event and couldn't work for months. Others on the plane were badly affected too. This is serious stuff and the 787 is great progress.

>"fume events" (leakage of combustion byproducts or oil fumes from the engine into the cabin)

is that why the cabin of airplanes smell like jet fuel for the first few minutes of rake-off?

Fume events are usually described as smelling like dirty socks or a wet dog. There was a fume event a few years ago that ended up going very badly for one of the pilots:

http://avherald.com/h?article=4b6eb830&opt=1024

The fuel smell at the beginning of the flight might just be happening because the engines and/or APU are ingesting the exhaust of the aircraft in front of you while on the taxiway, and some of that exhaust smell ends up in the bleed air that eventually enters the cabin.

I actually feel the difference most for B787, less exhausted and not as dehydrated after 8+ hour flights. A reason for me to book B787 wherever possible. I believe the A350 should be similar but wasn't able to test it yet on long-haul.

A380 is relatively quiet but air quality isn't really comparable with the Dreamliner.

I'm really curious what this is btw. I read so much about the 787 having a better cabin atmosphere but all my 787 flights where quite underwhealming and the automatically controlled window shades at least on two BA flights I was on where really frustrating because they simulated night until right the moment we were landing and then it propelled me into late afternoon sunlight conditions. I absolutely hated that sensation.

Can airplanes have a different cabin pressure? If so, maybe A380 has it higher, and in theory that should help to avoid dehydration.

Yes, newer aircraft have a lower cabin “altitude”. They also have higher humidity since there are more compositie materials and less risk of rust.

The A380 and 787 use exactly the same aircon packs, just more of them in the former case.

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